/*
 *  History:
 *  Started: Aug 9 by Lawrence Foard (entropy@world.std.com),
 *           to allow user process control of SCSI devices.
 *  Development Sponsored by Killy Corp. NY NY
 *
 * Original driver (sg.c):
 *        Copyright (C) 1992 Lawrence Foard
 * Version 2 and 3 extensions to driver:
 *        Copyright (C) 1998 - 2005 Douglas Gilbert
 *
 *  Modified  19-JAN-1998  Richard Gooch <rgooch@atnf.csiro.au>  Devfs support
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 */

static int sg_version_num = 30532;      /* 2 digits for each component */
#define SG_VERSION_STR "3.5.32"

/*
 *  D. P. Gilbert (dgilbert@interlog.com, dougg@triode.net.au), notes:
 *      - scsi logging is available via SCSI_LOG_TIMEOUT macros. First
 *        the kernel/module needs to be built with CONFIG_SCSI_LOGGING
 *        (otherwise the macros compile to empty statements).
 *
 */
#include <linux/config.h>
#include <linux/module.h>

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/mtio.h>
#include <linux/ioctl.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/smp_lock.h>
#include <linux/moduleparam.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/cdev.h>
#include <linux/seq_file.h>
#include <linux/blkdev.h>
#include <linux/delay.h>

#include "scsi.h"
#include <scsi/scsi_host.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_ioctl.h>
#include <scsi/sg.h>

#include "scsi_logging.h"

#ifdef CONFIG_SCSI_PROC_FS
#include <linux/proc_fs.h>
static char *sg_version_date = "20050117";

static int sg_proc_init(void);
static void sg_proc_cleanup(void);
#endif

#ifndef LINUX_VERSION_CODE
#include <linux/version.h>
#endif                          /* LINUX_VERSION_CODE */

#define SG_ALLOW_DIO_DEF 0
#define SG_ALLOW_DIO_CODE /* compile out by commenting this define */

#define SG_MAX_DEVS 32768

/*
 * Suppose you want to calculate the formula muldiv(x,m,d)=int(x * m / d)
 * Then when using 32 bit integers x * m may overflow during the calculation.
 * Replacing muldiv(x) by muldiv(x)=((x % d) * m) / d + int(x / d) * m
 * calculates the same, but prevents the overflow when both m and d
 * are "small" numbers (like HZ and USER_HZ).
 * Of course an overflow is inavoidable if the result of muldiv doesn't fit
 * in 32 bits.
 */
#define MULDIV(X,MUL,DIV) ((((X % DIV) * MUL) / DIV) + ((X / DIV) * MUL))

#define SG_DEFAULT_TIMEOUT MULDIV(SG_DEFAULT_TIMEOUT_USER, HZ, USER_HZ)

int sg_big_buff = SG_DEF_RESERVED_SIZE;
/* N.B. This variable is readable and writeable via
   /proc/scsi/sg/def_reserved_size . Each time sg_open() is called a buffer
   of this size (or less if there is not enough memory) will be reserved
   for use by this file descriptor. [Deprecated usage: this variable is also
   readable via /proc/sys/kernel/sg-big-buff if the sg driver is built into
   the kernel (i.e. it is not a module).] */
static int def_reserved_size = -1;      /* picks up init parameter */
static int sg_allow_dio = SG_ALLOW_DIO_DEF;

#define SG_SECTOR_SZ 512
#define SG_SECTOR_MSK (SG_SECTOR_SZ - 1)

#define SG_DEV_ARR_LUMP 32      /* amount to over allocate sg_dev_arr by */

static int sg_add(struct class_device *);
static void sg_remove(struct class_device *);

static Scsi_Request *dummy_cmdp;        /* only used for sizeof */

static DEFINE_RWLOCK(sg_dev_arr_lock);  /* Also used to lock
                                                           file descriptor list for device */

static struct class_interface sg_interface = {
        .add            = sg_add,
        .remove         = sg_remove,
};

typedef struct sg_scatter_hold { /* holding area for scsi scatter gather info */
        unsigned short k_use_sg; /* Count of kernel scatter-gather pieces */
        unsigned short sglist_len; /* size of malloc'd scatter-gather list ++ */
        unsigned bufflen;       /* Size of (aggregate) data buffer */
        unsigned b_malloc_len;  /* actual len malloc'ed in buffer */
        void *buffer;           /* Data buffer or scatter list (k_use_sg>0) */
        char dio_in_use;        /* 0->indirect IO (or mmap), 1->dio */
        unsigned char cmd_opcode; /* first byte of command */
} Sg_scatter_hold;

struct sg_device;               /* forward declarations */
struct sg_fd;

typedef struct sg_request {     /* SG_MAX_QUEUE requests outstanding per file */
        Scsi_Request *my_cmdp;  /* != 0  when request with lower levels */
        struct sg_request *nextrp;      /* NULL -> tail request (slist) */
        struct sg_fd *parentfp; /* NULL -> not in use */
        Sg_scatter_hold data;   /* hold buffer, perhaps scatter list */
        sg_io_hdr_t header;     /* scsi command+info, see <scsi/sg.h> */
        unsigned char sense_b[sizeof (dummy_cmdp->sr_sense_buffer)];
        char res_used;          /* 1 -> using reserve buffer, 0 -> not ... */
        char orphan;            /* 1 -> drop on sight, 0 -> normal */
        char sg_io_owned;       /* 1 -> packet belongs to SG_IO */
        volatile char done;     /* 0->before bh, 1->before read, 2->read */
} Sg_request;

typedef struct sg_fd {          /* holds the state of a file descriptor */
        struct sg_fd *nextfp;   /* NULL when last opened fd on this device */
        struct sg_device *parentdp;     /* owning device */
        wait_queue_head_t read_wait;    /* queue read until command done */
        rwlock_t rq_list_lock;  /* protect access to list in req_arr */
        int timeout;            /* defaults to SG_DEFAULT_TIMEOUT      */
        int timeout_user;       /* defaults to SG_DEFAULT_TIMEOUT_USER */
        Sg_scatter_hold reserve;        /* buffer held for this file descriptor */
        unsigned save_scat_len; /* original length of trunc. scat. element */
        Sg_request *headrp;     /* head of request slist, NULL->empty */
        struct fasync_struct *async_qp; /* used by asynchronous notification */
        Sg_request req_arr[SG_MAX_QUEUE];       /* used as singly-linked list */
        char low_dma;           /* as in parent but possibly overridden to 1 */
        char force_packid;      /* 1 -> pack_id input to read(), 0 -> ignored */
        volatile char closed;   /* 1 -> fd closed but request(s) outstanding */
        char cmd_q;             /* 1 -> allow command queuing, 0 -> don't */
        char next_cmd_len;      /* 0 -> automatic (def), >0 -> use on next write() */
        char keep_orphan;       /* 0 -> drop orphan (def), 1 -> keep for read() */
        char mmap_called;       /* 0 -> mmap() never called on this fd */
} Sg_fd;

typedef struct sg_device { /* holds the state of each scsi generic device */
        struct scsi_device *device;
        wait_queue_head_t o_excl_wait;  /* queue open() when O_EXCL in use */
        int sg_tablesize;       /* adapter's max scatter-gather table size */
        Sg_fd *headfp;          /* first open fd belonging to this device */
        volatile char detached; /* 0->attached, 1->detached pending removal */
        volatile char exclude;  /* opened for exclusive access */
        char sgdebug;           /* 0->off, 1->sense, 9->dump dev, 10-> all devs */
        struct gendisk *disk;
        struct cdev * cdev;     /* char_dev [sysfs: /sys/cdev/major/sg<n>] */
} Sg_device;

static int sg_fasync(int fd, struct file *filp, int mode);
static void sg_cmd_done(Scsi_Cmnd * SCpnt);     /* tasklet or soft irq callback */
static int sg_start_req(Sg_request * srp);
static void sg_finish_rem_req(Sg_request * srp);
static int sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size);
static int sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp,
                         int tablesize);
static ssize_t sg_new_read(Sg_fd * sfp, char __user *buf, size_t count,
                           Sg_request * srp);
static ssize_t sg_new_write(Sg_fd * sfp, const char __user *buf, size_t count,
                            int blocking, int read_only, Sg_request ** o_srp);
static int sg_common_write(Sg_fd * sfp, Sg_request * srp,
                           unsigned char *cmnd, int timeout, int blocking);
static int sg_u_iovec(sg_io_hdr_t * hp, int sg_num, int ind,
                      int wr_xf, int *countp, unsigned char __user **up);
static int sg_write_xfer(Sg_request * srp);
static int sg_read_xfer(Sg_request * srp);
static int sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer);
static void sg_remove_scat(Sg_scatter_hold * schp);
static void sg_build_reserve(Sg_fd * sfp, int req_size);
static void sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size);
static void sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp);
static char *sg_page_malloc(int rqSz, int lowDma, int *retSzp);
static void sg_page_free(char *buff, int size);
static Sg_fd *sg_add_sfp(Sg_device * sdp, int dev);
static int sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp);
static void __sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp);
static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id);
static Sg_request *sg_add_request(Sg_fd * sfp);
static int sg_remove_request(Sg_fd * sfp, Sg_request * srp);
static int sg_res_in_use(Sg_fd * sfp);
static int sg_allow_access(unsigned char opcode, char dev_type);
static int sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len);
static Sg_device *sg_get_dev(int dev);
static inline unsigned char *sg_scatg2virt(const struct scatterlist *sclp);
#ifdef CONFIG_SCSI_PROC_FS
static int sg_last_dev(void);
#endif

static Sg_device **sg_dev_arr = NULL;
static int sg_dev_max;
static int sg_nr_dev;

#define SZ_SG_HEADER sizeof(struct sg_header)
#define SZ_SG_IO_HDR sizeof(sg_io_hdr_t)
#define SZ_SG_IOVEC sizeof(sg_iovec_t)
#define SZ_SG_REQ_INFO sizeof(sg_req_info_t)

static int
sg_open(struct inode *inode, struct file *filp)
{
        int dev = iminor(inode);
        int flags = filp->f_flags;
        Sg_device *sdp;
        Sg_fd *sfp;
        int res;
        int retval;

        nonseekable_open(inode, filp);
        SCSI_LOG_TIMEOUT(3, printk("sg_open: dev=%d, flags=0x%x\n", dev, flags));
        sdp = sg_get_dev(dev);
        if ((!sdp) || (!sdp->device))
                return -ENXIO;
        if (sdp->detached)
                return -ENODEV;

        /* This driver's module count bumped by fops_get in <linux/fs.h> */
        /* Prevent the device driver from vanishing while we sleep */
        retval = scsi_device_get(sdp->device);
        if (retval)
                return retval;

        if (!((flags & O_NONBLOCK) ||
              scsi_block_when_processing_errors(sdp->device))) {
                retval = -ENXIO;
                /* we are in error recovery for this device */
                goto error_out;
        }

        if (flags & O_EXCL) {
                if (O_RDONLY == (flags & O_ACCMODE)) {
                        retval = -EPERM; /* Can't lock it with read only access */
                        goto error_out;
                }
                if (sdp->headfp && (flags & O_NONBLOCK)) {
                        retval = -EBUSY;
                        goto error_out;
                }
                res = 0;
                __wait_event_interruptible(sdp->o_excl_wait,
                        ((sdp->headfp || sdp->exclude) ? 0 : (sdp->exclude = 1)), res);
                if (res) {
                        retval = res;   /* -ERESTARTSYS because signal hit process */
                        goto error_out;
                }
        } else if (sdp->exclude) {      /* some other fd has an exclusive lock on dev */
                if (flags & O_NONBLOCK) {
                        retval = -EBUSY;
                        goto error_out;
                }
                res = 0;
                __wait_event_interruptible(sdp->o_excl_wait, (!sdp->exclude),
                                           res);
                if (res) {
                        retval = res;   /* -ERESTARTSYS because signal hit process */
                        goto error_out;
                }
        }
        if (sdp->detached) {
                retval = -ENODEV;
                goto error_out;
        }
        if (!sdp->headfp) {     /* no existing opens on this device */
                sdp->sgdebug = 0;
                sdp->sg_tablesize = sdp->device->host->sg_tablesize;
        }
        if ((sfp = sg_add_sfp(sdp, dev)))
                filp->private_data = sfp;
        else {
                if (flags & O_EXCL)
                        sdp->exclude = 0;       /* undo if error */
                retval = -ENOMEM;
                goto error_out;
        }
        return 0;

      error_out:
        scsi_device_put(sdp->device);
        return retval;
}

/* Following function was formerly called 'sg_close' */
static int
sg_release(struct inode *inode, struct file *filp)
{
        Sg_device *sdp;
        Sg_fd *sfp;

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_release: %s\n", sdp->disk->disk_name));
        sg_fasync(-1, filp, 0); /* remove filp from async notification list */
        if (0 == sg_remove_sfp(sdp, sfp)) {     /* Returns 1 when sdp gone */
                if (!sdp->detached) {
                        scsi_device_put(sdp->device);
                }
                sdp->exclude = 0;
                wake_up_interruptible(&sdp->o_excl_wait);
        }
        return 0;
}

static ssize_t
sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
{
        int k, res;
        Sg_device *sdp;
        Sg_fd *sfp;
        Sg_request *srp;
        int req_pack_id = -1;
        struct sg_header old_hdr;
        sg_io_hdr_t new_hdr;
        sg_io_hdr_t *hp;

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_read: %s, count=%d\n",
                                   sdp->disk->disk_name, (int) count));
        if ((k = verify_area(VERIFY_WRITE, buf, count)))
                return k;
        if (sfp->force_packid && (count >= SZ_SG_HEADER)) {
                if (__copy_from_user(&old_hdr, buf, SZ_SG_HEADER))
                        return -EFAULT;
                if (old_hdr.reply_len < 0) {
                        if (count >= SZ_SG_IO_HDR) {
                                if (__copy_from_user
                                    (&new_hdr, buf, SZ_SG_IO_HDR))
                                        return -EFAULT;
                                req_pack_id = new_hdr.pack_id;
                        }
                } else
                        req_pack_id = old_hdr.pack_id;
        }
        srp = sg_get_rq_mark(sfp, req_pack_id);
        if (!srp) {             /* now wait on packet to arrive */
                if (sdp->detached)
                        return -ENODEV;
                if (filp->f_flags & O_NONBLOCK)
                        return -EAGAIN;
                while (1) {
                        res = 0;        /* following is a macro that beats race condition */
                        __wait_event_interruptible(sfp->read_wait,
                                (sdp->detached || (srp = sg_get_rq_mark(sfp, req_pack_id))), 
                                                   res);
                        if (sdp->detached)
                                return -ENODEV;
                        if (0 == res)
                                break;
                        return res;     /* -ERESTARTSYS because signal hit process */
                }
        }
        if (srp->header.interface_id != '\0')
                return sg_new_read(sfp, buf, count, srp);

        hp = &srp->header;
        memset(&old_hdr, 0, SZ_SG_HEADER);
        old_hdr.reply_len = (int) hp->timeout;
        old_hdr.pack_len = old_hdr.reply_len; /* very old, strange behaviour */
        old_hdr.pack_id = hp->pack_id;
        old_hdr.twelve_byte =
            ((srp->data.cmd_opcode >= 0xc0) && (12 == hp->cmd_len)) ? 1 : 0;
        old_hdr.target_status = hp->masked_status;
        old_hdr.host_status = hp->host_status;
        old_hdr.driver_status = hp->driver_status;
        if ((CHECK_CONDITION & hp->masked_status) ||
            (DRIVER_SENSE & hp->driver_status))
                memcpy(old_hdr.sense_buffer, srp->sense_b,
                       sizeof (old_hdr.sense_buffer));
        switch (hp->host_status) {
        /* This setup of 'result' is for backward compatibility and is best
           ignored by the user who should use target, host + driver status */
        case DID_OK:
        case DID_PASSTHROUGH:
        case DID_SOFT_ERROR:
                old_hdr.result = 0;
                break;
        case DID_NO_CONNECT:
        case DID_BUS_BUSY:
        case DID_TIME_OUT:
                old_hdr.result = EBUSY;
                break;
        case DID_BAD_TARGET:
        case DID_ABORT:
        case DID_PARITY:
        case DID_RESET:
        case DID_BAD_INTR:
                old_hdr.result = EIO;
                break;
        case DID_ERROR:
                old_hdr.result = (srp->sense_b[0] == 0 && 
                                  hp->masked_status == GOOD) ? 0 : EIO;
                break;
        default:
                old_hdr.result = EIO;
                break;
        }

        /* Now copy the result back to the user buffer.  */
        if (count >= SZ_SG_HEADER) {
                if (__copy_to_user(buf, &old_hdr, SZ_SG_HEADER))
                        return -EFAULT;
                buf += SZ_SG_HEADER;
                if (count > old_hdr.reply_len)
                        count = old_hdr.reply_len;
                if (count > SZ_SG_HEADER) {
                        if ((res =
                             sg_read_oxfer(srp, buf, count - SZ_SG_HEADER)))
                                return -EFAULT;
                }
        } else
                count = (old_hdr.result == 0) ? 0 : -EIO;
        sg_finish_rem_req(srp);
        return count;
}

static ssize_t
sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp)
{
        sg_io_hdr_t *hp = &srp->header;
        int err = 0;
        int len;

        if (count < SZ_SG_IO_HDR) {
                err = -EINVAL;
                goto err_out;
        }
        hp->sb_len_wr = 0;
        if ((hp->mx_sb_len > 0) && hp->sbp) {
                if ((CHECK_CONDITION & hp->masked_status) ||
                    (DRIVER_SENSE & hp->driver_status)) {
                        int sb_len = sizeof (dummy_cmdp->sr_sense_buffer);
                        sb_len = (hp->mx_sb_len > sb_len) ? sb_len : hp->mx_sb_len;
                        len = 8 + (int) srp->sense_b[7];        /* Additional sense length field */
                        len = (len > sb_len) ? sb_len : len;
                        if (copy_to_user(hp->sbp, srp->sense_b, len)) {
                                err = -EFAULT;
                                goto err_out;
                        }
                        hp->sb_len_wr = len;
                }
        }
        if (hp->masked_status || hp->host_status || hp->driver_status)
                hp->info |= SG_INFO_CHECK;
        if (copy_to_user(buf, hp, SZ_SG_IO_HDR)) {
                err = -EFAULT;
                goto err_out;
        }
        err = sg_read_xfer(srp);
      err_out:
        sg_finish_rem_req(srp);
        return (0 == err) ? count : err;
}

static ssize_t
sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
{
        int mxsize, cmd_size, k;
        int input_size, blocking;
        unsigned char opcode;
        Sg_device *sdp;
        Sg_fd *sfp;
        Sg_request *srp;
        struct sg_header old_hdr;
        sg_io_hdr_t *hp;
        unsigned char cmnd[sizeof (dummy_cmdp->sr_cmnd)];

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_write: %s, count=%d\n",
                                   sdp->disk->disk_name, (int) count));
        if (sdp->detached)
                return -ENODEV;
        if (!((filp->f_flags & O_NONBLOCK) ||
              scsi_block_when_processing_errors(sdp->device)))
                return -ENXIO;

        if ((k = verify_area(VERIFY_READ, buf, count)))
                return k;       /* protects following copy_from_user()s + get_user()s */
        if (count < SZ_SG_HEADER)
                return -EIO;
        if (__copy_from_user(&old_hdr, buf, SZ_SG_HEADER))
                return -EFAULT;
        blocking = !(filp->f_flags & O_NONBLOCK);
        if (old_hdr.reply_len < 0)
                return sg_new_write(sfp, buf, count, blocking, 0, NULL);
        if (count < (SZ_SG_HEADER + 6))
                return -EIO;    /* The minimum scsi command length is 6 bytes. */

        if (!(srp = sg_add_request(sfp))) {
                SCSI_LOG_TIMEOUT(1, printk("sg_write: queue full\n"));
                return -EDOM;
        }
        buf += SZ_SG_HEADER;
        __get_user(opcode, buf);
        if (sfp->next_cmd_len > 0) {
                if (sfp->next_cmd_len > MAX_COMMAND_SIZE) {
                        SCSI_LOG_TIMEOUT(1, printk("sg_write: command length too long\n"));
                        sfp->next_cmd_len = 0;
                        sg_remove_request(sfp, srp);
                        return -EIO;
                }
                cmd_size = sfp->next_cmd_len;
                sfp->next_cmd_len = 0;  /* reset so only this write() effected */
        } else {
                cmd_size = COMMAND_SIZE(opcode);        /* based on SCSI command group */
                if ((opcode >= 0xc0) && old_hdr.twelve_byte)
                        cmd_size = 12;
        }
        SCSI_LOG_TIMEOUT(4, printk(
                "sg_write:   scsi opcode=0x%02x, cmd_size=%d\n", (int) opcode, cmd_size));
/* Determine buffer size.  */
        input_size = count - cmd_size;
        mxsize = (input_size > old_hdr.reply_len) ? input_size : old_hdr.reply_len;
        mxsize -= SZ_SG_HEADER;
        input_size -= SZ_SG_HEADER;
        if (input_size < 0) {
                sg_remove_request(sfp, srp);
                return -EIO;    /* User did not pass enough bytes for this command. */
        }
        hp = &srp->header;
        hp->interface_id = '\0';        /* indicator of old interface tunnelled */
        hp->cmd_len = (unsigned char) cmd_size;
        hp->iovec_count = 0;
        hp->mx_sb_len = 0;
        if (input_size > 0)
                hp->dxfer_direction = (old_hdr.reply_len > SZ_SG_HEADER) ?
                    SG_DXFER_TO_FROM_DEV : SG_DXFER_TO_DEV;
        else
                hp->dxfer_direction = (mxsize > 0) ? SG_DXFER_FROM_DEV : SG_DXFER_NONE;
        hp->dxfer_len = mxsize;
        hp->dxferp = (char __user *)buf + cmd_size;
        hp->sbp = NULL;
        hp->timeout = old_hdr.reply_len;        /* structure abuse ... */
        hp->flags = input_size; /* structure abuse ... */
        hp->pack_id = old_hdr.pack_id;
        hp->usr_ptr = NULL;
        if (__copy_from_user(cmnd, buf, cmd_size))
                return -EFAULT;
        /*
         * SG_DXFER_TO_FROM_DEV is functionally equivalent to SG_DXFER_FROM_DEV,
         * but is is possible that the app intended SG_DXFER_TO_DEV, because there
         * is a non-zero input_size, so emit a warning.
         */
        if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV)
                if (printk_ratelimit())
                        printk(KERN_WARNING
                               "sg_write: data in/out %d/%d bytes for SCSI command 0x%x--"
                               "guessing data in;\n" KERN_WARNING "   "
                               "program %s not setting count and/or reply_len properly\n",
                               old_hdr.reply_len - (int)SZ_SG_HEADER,
                               input_size, (unsigned int) cmnd[0],
                               current->comm);
        k = sg_common_write(sfp, srp, cmnd, sfp->timeout, blocking);
        return (k < 0) ? k : count;
}

static ssize_t
sg_new_write(Sg_fd * sfp, const char __user *buf, size_t count,
             int blocking, int read_only, Sg_request ** o_srp)
{
        int k;
        Sg_request *srp;
        sg_io_hdr_t *hp;
        unsigned char cmnd[sizeof (dummy_cmdp->sr_cmnd)];
        int timeout;
        unsigned long ul_timeout;

        if (count < SZ_SG_IO_HDR)
                return -EINVAL;
        if ((k = verify_area(VERIFY_READ, buf, count)))
                return k; /* protects following copy_from_user()s + get_user()s */

        sfp->cmd_q = 1; /* when sg_io_hdr seen, set command queuing on */
        if (!(srp = sg_add_request(sfp))) {
                SCSI_LOG_TIMEOUT(1, printk("sg_new_write: queue full\n"));
                return -EDOM;
        }
        hp = &srp->header;
        if (__copy_from_user(hp, buf, SZ_SG_IO_HDR)) {
                sg_remove_request(sfp, srp);
                return -EFAULT;
        }
        if (hp->interface_id != 'S') {
                sg_remove_request(sfp, srp);
                return -ENOSYS;
        }
        if (hp->flags & SG_FLAG_MMAP_IO) {
                if (hp->dxfer_len > sfp->reserve.bufflen) {
                        sg_remove_request(sfp, srp);
                        return -ENOMEM; /* MMAP_IO size must fit in reserve buffer */
                }
                if (hp->flags & SG_FLAG_DIRECT_IO) {
                        sg_remove_request(sfp, srp);
                        return -EINVAL; /* either MMAP_IO or DIRECT_IO (not both) */
                }
                if (sg_res_in_use(sfp)) {
                        sg_remove_request(sfp, srp);
                        return -EBUSY;  /* reserve buffer already being used */
                }
        }
        ul_timeout = msecs_to_jiffies(srp->header.timeout);
        timeout = (ul_timeout < INT_MAX) ? ul_timeout : INT_MAX;
        if ((!hp->cmdp) || (hp->cmd_len < 6) || (hp->cmd_len > sizeof (cmnd))) {
                sg_remove_request(sfp, srp);
                return -EMSGSIZE;
        }
        if ((k = verify_area(VERIFY_READ, hp->cmdp, hp->cmd_len))) {
                sg_remove_request(sfp, srp);
                return k;       /* protects following copy_from_user()s + get_user()s */
        }
        if (__copy_from_user(cmnd, hp->cmdp, hp->cmd_len)) {
                sg_remove_request(sfp, srp);
                return -EFAULT;
        }
        if (read_only &&
            (!sg_allow_access(cmnd[0], sfp->parentdp->device->type))) {
                sg_remove_request(sfp, srp);
                return -EPERM;
        }
        k = sg_common_write(sfp, srp, cmnd, timeout, blocking);
        if (k < 0)
                return k;
        if (o_srp)
                *o_srp = srp;
        return count;
}

static int
sg_common_write(Sg_fd * sfp, Sg_request * srp,
                unsigned char *cmnd, int timeout, int blocking)
{
        int k;
        Scsi_Request *SRpnt;
        Sg_device *sdp = sfp->parentdp;
        sg_io_hdr_t *hp = &srp->header;
        request_queue_t *q;

        srp->data.cmd_opcode = cmnd[0]; /* hold opcode of command */
        hp->status = 0;
        hp->masked_status = 0;
        hp->msg_status = 0;
        hp->info = 0;
        hp->host_status = 0;
        hp->driver_status = 0;
        hp->resid = 0;
        SCSI_LOG_TIMEOUT(4, printk("sg_common_write:  scsi opcode=0x%02x, cmd_size=%d\n",
                          (int) cmnd[0], (int) hp->cmd_len));

        if ((k = sg_start_req(srp))) {
                SCSI_LOG_TIMEOUT(1, printk("sg_write: start_req err=%d\n", k));
                sg_finish_rem_req(srp);
                return k;       /* probably out of space --> ENOMEM */
        }
        if ((k = sg_write_xfer(srp))) {
                SCSI_LOG_TIMEOUT(1, printk("sg_write: write_xfer, bad address\n"));
                sg_finish_rem_req(srp);
                return k;
        }
        if (sdp->detached) {
                sg_finish_rem_req(srp);
                return -ENODEV;
        }
        SRpnt = scsi_allocate_request(sdp->device, GFP_ATOMIC);
        if (SRpnt == NULL) {
                SCSI_LOG_TIMEOUT(1, printk("sg_write: no mem\n"));
                sg_finish_rem_req(srp);
                return -ENOMEM;
        }

        srp->my_cmdp = SRpnt;
        q = SRpnt->sr_device->request_queue;
        SRpnt->sr_request->rq_disk = sdp->disk;
        SRpnt->sr_sense_buffer[0] = 0;
        SRpnt->sr_cmd_len = hp->cmd_len;
        SRpnt->sr_use_sg = srp->data.k_use_sg;
        SRpnt->sr_sglist_len = srp->data.sglist_len;
        SRpnt->sr_bufflen = srp->data.bufflen;
        SRpnt->sr_underflow = 0;
        SRpnt->sr_buffer = srp->data.buffer;
        switch (hp->dxfer_direction) {
        case SG_DXFER_TO_FROM_DEV:
        case SG_DXFER_FROM_DEV:
                SRpnt->sr_data_direction = SCSI_DATA_READ;
                break;
        case SG_DXFER_TO_DEV:
                SRpnt->sr_data_direction = SCSI_DATA_WRITE;
                break;
        case SG_DXFER_UNKNOWN:
                SRpnt->sr_data_direction = SCSI_DATA_UNKNOWN;
                break;
        default:
                SRpnt->sr_data_direction = SCSI_DATA_NONE;
                break;
        }
        SRpnt->upper_private_data = srp;
        srp->data.k_use_sg = 0;
        srp->data.sglist_len = 0;
        srp->data.bufflen = 0;
        srp->data.buffer = NULL;
        hp->duration = jiffies; /* unit jiffies now, millisecs after done */
/* Now send everything of to mid-level. The next time we hear about this
   packet is when sg_cmd_done() is called (i.e. a callback). */
        scsi_do_req(SRpnt, (void *) cmnd,
                    (void *) SRpnt->sr_buffer, hp->dxfer_len,
                    sg_cmd_done, timeout, SG_DEFAULT_RETRIES);
        /* dxfer_len overwrites SRpnt->sr_bufflen, hence need for b_malloc_len */
        return 0;
}

static int
sg_srp_done(Sg_request *srp, Sg_fd *sfp)
{
        unsigned long iflags;
        int done;

        read_lock_irqsave(&sfp->rq_list_lock, iflags);
        done = srp->done;
        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return done;
}

static int
sg_ioctl(struct inode *inode, struct file *filp,
         unsigned int cmd_in, unsigned long arg)
{
        void __user *p = (void __user *)arg;
        int __user *ip = p;
        int result, val, read_only;
        Sg_device *sdp;
        Sg_fd *sfp;
        Sg_request *srp;
        unsigned long iflags;

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_ioctl: %s, cmd=0x%x\n",
                                   sdp->disk->disk_name, (int) cmd_in));
        read_only = (O_RDWR != (filp->f_flags & O_ACCMODE));

        switch (cmd_in) {
        case SG_IO:
                {
                        int blocking = 1;       /* ignore O_NONBLOCK flag */

                        if (sdp->detached)
                                return -ENODEV;
                        if (!scsi_block_when_processing_errors(sdp->device))
                                return -ENXIO;
                        result = verify_area(VERIFY_WRITE, p, SZ_SG_IO_HDR);
                        if (result)
                                return result;
                        result =
                            sg_new_write(sfp, p, SZ_SG_IO_HDR,
                                         blocking, read_only, &srp);
                        if (result < 0)
                                return result;
                        srp->sg_io_owned = 1;
                        while (1) {
                                result = 0;     /* following macro to beat race condition */
                                __wait_event_interruptible(sfp->read_wait,
                                        (sdp->detached || sfp->closed || sg_srp_done(srp, sfp)),
                                                           result);
                                if (sdp->detached)
                                        return -ENODEV;
                                if (sfp->closed)
                                        return 0;       /* request packet dropped already */
                                if (0 == result)
                                        break;
                                srp->orphan = 1;
                                return result;  /* -ERESTARTSYS because signal hit process */
                        }
                        write_lock_irqsave(&sfp->rq_list_lock, iflags);
                        srp->done = 2;
                        write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
                        result = sg_new_read(sfp, p, SZ_SG_IO_HDR, srp);
                        return (result < 0) ? result : 0;
                }
        case SG_SET_TIMEOUT:
                result = get_user(val, ip);
                if (result)
                        return result;
                if (val < 0)
                        return -EIO;
                if (val >= MULDIV (INT_MAX, USER_HZ, HZ))
                    val = MULDIV (INT_MAX, USER_HZ, HZ);
                sfp->timeout_user = val;
                sfp->timeout = MULDIV (val, HZ, USER_HZ);

                return 0;
        case SG_GET_TIMEOUT:    /* N.B. User receives timeout as return value */
                                /* strange ..., for backward compatibility */
                return sfp->timeout_user;
        case SG_SET_FORCE_LOW_DMA:
                result = get_user(val, ip);
                if (result)
                        return result;
                if (val) {
                        sfp->low_dma = 1;
                        if ((0 == sfp->low_dma) && (0 == sg_res_in_use(sfp))) {
                                val = (int) sfp->reserve.bufflen;
                                sg_remove_scat(&sfp->reserve);
                                sg_build_reserve(sfp, val);
                        }
                } else {
                        if (sdp->detached)
                                return -ENODEV;
                        sfp->low_dma = sdp->device->host->unchecked_isa_dma;
                }
                return 0;
        case SG_GET_LOW_DMA:
                return put_user((int) sfp->low_dma, ip);
        case SG_GET_SCSI_ID:
                result =
                    verify_area(VERIFY_WRITE, p, sizeof (sg_scsi_id_t));
                if (result)
                        return result;
                else {
                        sg_scsi_id_t __user *sg_idp = p;

                        if (sdp->detached)
                                return -ENODEV;
                        __put_user((int) sdp->device->host->host_no,
                                   &sg_idp->host_no);
                        __put_user((int) sdp->device->channel,
                                   &sg_idp->channel);
                        __put_user((int) sdp->device->id, &sg_idp->scsi_id);
                        __put_user((int) sdp->device->lun, &sg_idp->lun);
                        __put_user((int) sdp->device->type, &sg_idp->scsi_type);
                        __put_user((short) sdp->device->host->cmd_per_lun,
                                   &sg_idp->h_cmd_per_lun);
                        __put_user((short) sdp->device->queue_depth,
                                   &sg_idp->d_queue_depth);
                        __put_user(0, &sg_idp->unused[0]);
                        __put_user(0, &sg_idp->unused[1]);
                        return 0;
                }
        case SG_SET_FORCE_PACK_ID:
                result = get_user(val, ip);
                if (result)
                        return result;
                sfp->force_packid = val ? 1 : 0;
                return 0;
        case SG_GET_PACK_ID:
                result = verify_area(VERIFY_WRITE, ip, sizeof (int));
                if (result)
                        return result;
                read_lock_irqsave(&sfp->rq_list_lock, iflags);
                for (srp = sfp->headrp; srp; srp = srp->nextrp) {
                        if ((1 == srp->done) && (!srp->sg_io_owned)) {
                                read_unlock_irqrestore(&sfp->rq_list_lock,
                                                       iflags);
                                __put_user(srp->header.pack_id, ip);
                                return 0;
                        }
                }
                read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
                __put_user(-1, ip);
                return 0;
        case SG_GET_NUM_WAITING:
                read_lock_irqsave(&sfp->rq_list_lock, iflags);
                for (val = 0, srp = sfp->headrp; srp; srp = srp->nextrp) {
                        if ((1 == srp->done) && (!srp->sg_io_owned))
                                ++val;
                }
                read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
                return put_user(val, ip);
        case SG_GET_SG_TABLESIZE:
                return put_user(sdp->sg_tablesize, ip);
        case SG_SET_RESERVED_SIZE:
                result = get_user(val, ip);
                if (result)
                        return result;
                if (val < 0)
                        return -EINVAL;
                if (val != sfp->reserve.bufflen) {
                        if (sg_res_in_use(sfp) || sfp->mmap_called)
                                return -EBUSY;
                        sg_remove_scat(&sfp->reserve);
                        sg_build_reserve(sfp, val);
                }
                return 0;
        case SG_GET_RESERVED_SIZE:
                val = (int) sfp->reserve.bufflen;
                return put_user(val, ip);
        case SG_SET_COMMAND_Q:
                result = get_user(val, ip);
                if (result)
                        return result;
                sfp->cmd_q = val ? 1 : 0;
                return 0;
        case SG_GET_COMMAND_Q:
                return put_user((int) sfp->cmd_q, ip);
        case SG_SET_KEEP_ORPHAN:
                result = get_user(val, ip);
                if (result)
                        return result;
                sfp->keep_orphan = val;
                return 0;
        case SG_GET_KEEP_ORPHAN:
                return put_user((int) sfp->keep_orphan, ip);
        case SG_NEXT_CMD_LEN:
                result = get_user(val, ip);
                if (result)
                        return result;
                sfp->next_cmd_len = (val > 0) ? val : 0;
                return 0;
        case SG_GET_VERSION_NUM:
                return put_user(sg_version_num, ip);
        case SG_GET_ACCESS_COUNT:
                /* faked - we don't have a real access count anymore */
                val = (sdp->device ? 1 : 0);
                return put_user(val, ip);
        case SG_GET_REQUEST_TABLE:
                result = verify_area(VERIFY_WRITE, p,
                                     SZ_SG_REQ_INFO * SG_MAX_QUEUE);
                if (result)
                        return result;
                else {
                        sg_req_info_t rinfo[SG_MAX_QUEUE];
                        Sg_request *srp;
                        read_lock_irqsave(&sfp->rq_list_lock, iflags);
                        for (srp = sfp->headrp, val = 0; val < SG_MAX_QUEUE;
                             ++val, srp = srp ? srp->nextrp : srp) {
                                memset(&rinfo[val], 0, SZ_SG_REQ_INFO);
                                if (srp) {
                                        rinfo[val].req_state = srp->done + 1;
                                        rinfo[val].problem =
                                            srp->header.masked_status & 
                                            srp->header.host_status & 
                                            srp->header.driver_status;
                                        rinfo[val].duration =
                                            srp->done ? srp->header.duration :
                                            jiffies_to_msecs(
                                                jiffies - srp->header.duration);
                                        rinfo[val].orphan = srp->orphan;
                                        rinfo[val].sg_io_owned = srp->sg_io_owned;
                                        rinfo[val].pack_id = srp->header.pack_id;
                                        rinfo[val].usr_ptr = srp->header.usr_ptr;
                                }
                        }
                        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
                        return (__copy_to_user(p, rinfo,
                                SZ_SG_REQ_INFO * SG_MAX_QUEUE) ? -EFAULT : 0);
                }
        case SG_EMULATED_HOST:
                if (sdp->detached)
                        return -ENODEV;
                return put_user(sdp->device->host->hostt->emulated, ip);
        case SG_SCSI_RESET:
                if (sdp->detached)
                        return -ENODEV;
                if (filp->f_flags & O_NONBLOCK) {
                        if (test_bit(SHOST_RECOVERY,
                                     &sdp->device->host->shost_state))
                                return -EBUSY;
                } else if (!scsi_block_when_processing_errors(sdp->device))
                        return -EBUSY;
                result = get_user(val, ip);
                if (result)
                        return result;
                if (SG_SCSI_RESET_NOTHING == val)
                        return 0;
                switch (val) {
                case SG_SCSI_RESET_DEVICE:
                        val = SCSI_TRY_RESET_DEVICE;
                        break;
                case SG_SCSI_RESET_BUS:
                        val = SCSI_TRY_RESET_BUS;
                        break;
                case SG_SCSI_RESET_HOST:
                        val = SCSI_TRY_RESET_HOST;
                        break;
                default:

                        return -EINVAL;
                }
                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                        return -EACCES;
                return (scsi_reset_provider(sdp->device, val) ==
                        SUCCESS) ? 0 : -EIO;
        case SCSI_IOCTL_SEND_COMMAND:
                if (sdp->detached)
                        return -ENODEV;
                if (read_only) {
                        unsigned char opcode = WRITE_6;
                        Scsi_Ioctl_Command __user *siocp = p;

                        if (copy_from_user(&opcode, siocp->data, 1))
                                return -EFAULT;
                        if (!sg_allow_access(opcode, sdp->device->type))
                                return -EPERM;
                }
                return scsi_ioctl_send_command(sdp->device, p);
        case SG_SET_DEBUG:
                result = get_user(val, ip);
                if (result)
                        return result;
                sdp->sgdebug = (char) val;
                return 0;
        case SCSI_IOCTL_GET_IDLUN:
        case SCSI_IOCTL_GET_BUS_NUMBER:
        case SCSI_IOCTL_PROBE_HOST:
        case SG_GET_TRANSFORM:
                if (sdp->detached)
                        return -ENODEV;
                return scsi_ioctl(sdp->device, cmd_in, p);
        default:
                if (read_only)
                        return -EPERM;  /* don't know so take safe approach */
                return scsi_ioctl(sdp->device, cmd_in, p);
        }
}

static unsigned int
sg_poll(struct file *filp, poll_table * wait)
{
        unsigned int res = 0;
        Sg_device *sdp;
        Sg_fd *sfp;
        Sg_request *srp;
        int count = 0;
        unsigned long iflags;

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp))
            || sfp->closed)
                return POLLERR;
        poll_wait(filp, &sfp->read_wait, wait);
        read_lock_irqsave(&sfp->rq_list_lock, iflags);
        for (srp = sfp->headrp; srp; srp = srp->nextrp) {
                /* if any read waiting, flag it */
                if ((0 == res) && (1 == srp->done) && (!srp->sg_io_owned))
                        res = POLLIN | POLLRDNORM;
                ++count;
        }
        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);

        if (sdp->detached)
                res |= POLLHUP;
        else if (!sfp->cmd_q) {
                if (0 == count)
                        res |= POLLOUT | POLLWRNORM;
        } else if (count < SG_MAX_QUEUE)
                res |= POLLOUT | POLLWRNORM;
        SCSI_LOG_TIMEOUT(3, printk("sg_poll: %s, res=0x%x\n",
                                   sdp->disk->disk_name, (int) res));
        return res;
}

static int
sg_fasync(int fd, struct file *filp, int mode)
{
        int retval;
        Sg_device *sdp;
        Sg_fd *sfp;

        if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_fasync: %s, mode=%d\n",
                                   sdp->disk->disk_name, mode));

        retval = fasync_helper(fd, filp, mode, &sfp->async_qp);
        return (retval < 0) ? retval : 0;
}

static inline unsigned char *
sg_scatg2virt(const struct scatterlist *sclp)
{
        return (sclp && sclp->page) ?
            (unsigned char *) page_address(sclp->page) + sclp->offset : NULL;
}

/* When startFinish==1 increments page counts for pages other than the 
   first of scatter gather elements obtained from __get_free_pages().
   When startFinish==0 decrements ... */
static void
sg_rb_correct4mmap(Sg_scatter_hold * rsv_schp, int startFinish)
{
        void *page_ptr;
        struct page *page;
        int k, m;

        SCSI_LOG_TIMEOUT(3, printk("sg_rb_correct4mmap: startFinish=%d, scatg=%d\n", 
                                   startFinish, rsv_schp->k_use_sg));
        /* N.B. correction _not_ applied to base page of each allocation */
        if (rsv_schp->k_use_sg) {       /* reserve buffer is a scatter gather list */
                struct scatterlist *sclp = rsv_schp->buffer;

                for (k = 0; k < rsv_schp->k_use_sg; ++k, ++sclp) {
                        for (m = PAGE_SIZE; m < sclp->length; m += PAGE_SIZE) {
                                page_ptr = sg_scatg2virt(sclp) + m;
                                page = virt_to_page(page_ptr);
                                if (startFinish)
                                        get_page(page);
                                else {
                                        if (page_count(page) > 0)
                                                __put_page(page);
                                }
                        }
                }
        } else {                /* reserve buffer is just a single allocation */
                for (m = PAGE_SIZE; m < rsv_schp->bufflen; m += PAGE_SIZE) {
                        page_ptr = (unsigned char *) rsv_schp->buffer + m;
                        page = virt_to_page(page_ptr);
                        if (startFinish)
                                get_page(page);
                        else {
                                if (page_count(page) > 0)
                                        __put_page(page);
                        }
                }
        }
}

static struct page *
sg_vma_nopage(struct vm_area_struct *vma, unsigned long addr, int *type)
{
        Sg_fd *sfp;
        struct page *page = NOPAGE_SIGBUS;
        void *page_ptr = NULL;
        unsigned long offset;
        Sg_scatter_hold *rsv_schp;

        if ((NULL == vma) || (!(sfp = (Sg_fd *) vma->vm_private_data)))
                return page;
        rsv_schp = &sfp->reserve;
        offset = addr - vma->vm_start;
        if (offset >= rsv_schp->bufflen)
                return page;
        SCSI_LOG_TIMEOUT(3, printk("sg_vma_nopage: offset=%lu, scatg=%d\n",
                                   offset, rsv_schp->k_use_sg));
        if (rsv_schp->k_use_sg) {       /* reserve buffer is a scatter gather list */
                int k;
                unsigned long sa = vma->vm_start;
                unsigned long len;
                struct scatterlist *sclp = rsv_schp->buffer;

                for (k = 0; (k < rsv_schp->k_use_sg) && (sa < vma->vm_end);
                     ++k, ++sclp) {
                        len = vma->vm_end - sa;
                        len = (len < sclp->length) ? len : sclp->length;
                        if (offset < len) {
                                page_ptr = sg_scatg2virt(sclp) + offset;
                                page = virt_to_page(page_ptr);
                                get_page(page); /* increment page count */
                                break;
                        }
                        sa += len;
                        offset -= len;
                }
        } else {                /* reserve buffer is just a single allocation */
                page_ptr = (unsigned char *) rsv_schp->buffer + offset;
                page = virt_to_page(page_ptr);
                get_page(page); /* increment page count */
        }
        if (type)
                *type = VM_FAULT_MINOR;
        return page;
}

static struct vm_operations_struct sg_mmap_vm_ops = {
        .nopage = sg_vma_nopage,
};

static int
sg_mmap(struct file *filp, struct vm_area_struct *vma)
{
        Sg_fd *sfp;
        unsigned long req_sz = vma->vm_end - vma->vm_start;
        Sg_scatter_hold *rsv_schp;

        if ((!filp) || (!vma) || (!(sfp = (Sg_fd *) filp->private_data)))
                return -ENXIO;
        SCSI_LOG_TIMEOUT(3, printk("sg_mmap starting, vm_start=%p, len=%d\n",
                                   (void *) vma->vm_start, (int) req_sz));
        if (vma->vm_pgoff)
                return -EINVAL; /* want no offset */
        rsv_schp = &sfp->reserve;
        if (req_sz > rsv_schp->bufflen)
                return -ENOMEM; /* cannot map more than reserved buffer */

        if (rsv_schp->k_use_sg) { /* reserve buffer is a scatter gather list */
                int k;
                unsigned long sa = vma->vm_start;
                unsigned long len;
                struct scatterlist *sclp = rsv_schp->buffer;

                for (k = 0; (k < rsv_schp->k_use_sg) && (sa < vma->vm_end);
                     ++k, ++sclp) {
                        if (0 != sclp->offset)
                                return -EFAULT; /* non page aligned memory ?? */
                        len = vma->vm_end - sa;
                        len = (len < sclp->length) ? len : sclp->length;
                        sa += len;
                }
        } else {        /* reserve buffer is just a single allocation */
                if ((unsigned long) rsv_schp->buffer & (PAGE_SIZE - 1))
                        return -EFAULT; /* non page aligned memory ?? */
        }
        if (0 == sfp->mmap_called) {
                sg_rb_correct4mmap(rsv_schp, 1);        /* do only once per fd lifetime */
                sfp->mmap_called = 1;
        }
        vma->vm_flags |= (VM_RESERVED | VM_IO);
        vma->vm_private_data = sfp;
        vma->vm_ops = &sg_mmap_vm_ops;
        return 0;
}

/* This function is a "bottom half" handler that is called by the
 * mid level when a command is completed (or has failed). */
static void
sg_cmd_done(Scsi_Cmnd * SCpnt)
{
        Scsi_Request *SRpnt = NULL;
        Sg_device *sdp = NULL;
        Sg_fd *sfp;
        Sg_request *srp = NULL;
        unsigned long iflags;

        if (SCpnt && (SRpnt = SCpnt->sc_request))
                srp = (Sg_request *) SRpnt->upper_private_data;
        if (NULL == srp) {
                printk(KERN_ERR "sg_cmd_done: NULL request\n");
                if (SRpnt)
                        scsi_release_request(SRpnt);
                return;
        }
        sfp = srp->parentfp;
        if (sfp)
                sdp = sfp->parentdp;
        if ((NULL == sdp) || sdp->detached) {
                printk(KERN_INFO "sg_cmd_done: device detached\n");
                scsi_release_request(SRpnt);
                return;
        }

        /* First transfer ownership of data buffers to sg_device object. */
        srp->data.k_use_sg = SRpnt->sr_use_sg;
        srp->data.sglist_len = SRpnt->sr_sglist_len;
        srp->data.bufflen = SRpnt->sr_bufflen;
        srp->data.buffer = SRpnt->sr_buffer;
        /* now clear out request structure */
        SRpnt->sr_use_sg = 0;
        SRpnt->sr_sglist_len = 0;
        SRpnt->sr_bufflen = 0;
        SRpnt->sr_buffer = NULL;
        SRpnt->sr_underflow = 0;
        SRpnt->sr_request->rq_disk = NULL; /* "sg" _disowns_ request blk */

        srp->my_cmdp = NULL;

        SCSI_LOG_TIMEOUT(4, printk("sg_cmd_done: %s, pack_id=%d, res=0x%x\n",
                sdp->disk->disk_name, srp->header.pack_id, (int) SRpnt->sr_result));
        srp->header.resid = SCpnt->resid;
        /* N.B. unit of duration changes here from jiffies to millisecs */
        srp->header.duration =
            jiffies_to_msecs(jiffies - srp->header.duration);
        if (0 != SRpnt->sr_result) {
                struct scsi_sense_hdr sshdr;

                memcpy(srp->sense_b, SRpnt->sr_sense_buffer,
                       sizeof (srp->sense_b));
                srp->header.status = 0xff & SRpnt->sr_result;
                srp->header.masked_status = status_byte(SRpnt->sr_result);
                srp->header.msg_status = msg_byte(SRpnt->sr_result);
                srp->header.host_status = host_byte(SRpnt->sr_result);
                srp->header.driver_status = driver_byte(SRpnt->sr_result);
                if ((sdp->sgdebug > 0) &&
                    ((CHECK_CONDITION == srp->header.masked_status) ||
                     (COMMAND_TERMINATED == srp->header.masked_status)))
                        print_req_sense("sg_cmd_done", SRpnt);

                /* Following if statement is a patch supplied by Eric Youngdale */
                if (driver_byte(SRpnt->sr_result) != 0
                    && scsi_command_normalize_sense(SCpnt, &sshdr)
                    && !scsi_sense_is_deferred(&sshdr)
                    && sshdr.sense_key == UNIT_ATTENTION
                    && sdp->device->removable) {
                        /* Detected possible disc change. Set the bit - this */
                        /* may be used if there are filesystems using this device */
                        sdp->device->changed = 1;
                }
        }
        /* Rely on write phase to clean out srp status values, so no "else" */

        scsi_release_request(SRpnt);
        SRpnt = NULL;
        if (sfp->closed) {      /* whoops this fd already released, cleanup */
                SCSI_LOG_TIMEOUT(1, printk("sg_cmd_done: already closed, freeing ...\n"));
                sg_finish_rem_req(srp);
                srp = NULL;
                if (NULL == sfp->headrp) {
                        SCSI_LOG_TIMEOUT(1, printk("sg...bh: already closed, final cleanup\n"));
                        if (0 == sg_remove_sfp(sdp, sfp)) {     /* device still present */
                                scsi_device_put(sdp->device);
                        }
                        sfp = NULL;
                }
        } else if (srp && srp->orphan) {
                if (sfp->keep_orphan)
                        srp->sg_io_owned = 0;
                else {
                        sg_finish_rem_req(srp);
                        srp = NULL;
                }
        }
        if (sfp && srp) {
                /* Now wake up any sg_read() that is waiting for this packet. */
                kill_fasync(&sfp->async_qp, SIGPOLL, POLL_IN);
                write_lock_irqsave(&sfp->rq_list_lock, iflags);
                srp->done = 1;
                wake_up_interruptible(&sfp->read_wait);
                write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        }
}

static struct file_operations sg_fops = {
        .owner = THIS_MODULE,
        .read = sg_read,
        .write = sg_write,
        .poll = sg_poll,
        .ioctl = sg_ioctl,
        .open = sg_open,
        .mmap = sg_mmap,
        .release = sg_release,
        .fasync = sg_fasync,
};

static struct class_simple * sg_sysfs_class;

static int sg_sysfs_valid = 0;

static int sg_alloc(struct gendisk *disk, struct scsi_device *scsidp)
{
        Sg_device *sdp;
        unsigned long iflags;
        void *old_sg_dev_arr = NULL;
        int k, error;

        sdp = kmalloc(sizeof(Sg_device), GFP_KERNEL);
        if (!sdp) {
                printk(KERN_WARNING "kmalloc Sg_device failure\n");
                return -ENOMEM;
        }

        write_lock_irqsave(&sg_dev_arr_lock, iflags);
        if (unlikely(sg_nr_dev >= sg_dev_max)) {        /* try to resize */
                Sg_device **tmp_da;
                int tmp_dev_max = sg_nr_dev + SG_DEV_ARR_LUMP;
                write_unlock_irqrestore(&sg_dev_arr_lock, iflags);

                tmp_da = kmalloc(tmp_dev_max * sizeof(Sg_device *), GFP_KERNEL);
                if (unlikely(!tmp_da))
                        goto expand_failed;

                write_lock_irqsave(&sg_dev_arr_lock, iflags);
                memset(tmp_da, 0, tmp_dev_max * sizeof(Sg_device *));
                memcpy(tmp_da, sg_dev_arr, sg_dev_max * sizeof(Sg_device *));
                old_sg_dev_arr = sg_dev_arr;
                sg_dev_arr = tmp_da;
                sg_dev_max = tmp_dev_max;
        }

        for (k = 0; k < sg_dev_max; k++)
                if (!sg_dev_arr[k])
                        break;
        if (unlikely(k >= SG_MAX_DEVS))
                goto overflow;

        memset(sdp, 0, sizeof(*sdp));
        SCSI_LOG_TIMEOUT(3, printk("sg_alloc: dev=%d \n", k));
        sprintf(disk->disk_name, "sg%d", k);
        disk->first_minor = k;
        sdp->disk = disk;
        sdp->device = scsidp;
        init_waitqueue_head(&sdp->o_excl_wait);
        sdp->sg_tablesize = scsidp->host ? scsidp->host->sg_tablesize : 0;

        sg_nr_dev++;
        sg_dev_arr[k] = sdp;
        write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        error = k;

 out:
        if (error < 0)
                kfree(sdp);
        kfree(old_sg_dev_arr);
        return error;

 expand_failed:
        printk(KERN_WARNING "sg_alloc: device array cannot be resized\n");
        error = -ENOMEM;
        goto out;

 overflow:
        write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        printk(KERN_WARNING
               "Unable to attach sg device <%d, %d, %d, %d> type=%d, minor "
               "number exceeds %d\n", scsidp->host->host_no, scsidp->channel,
               scsidp->id, scsidp->lun, scsidp->type, SG_MAX_DEVS - 1);
        error = -ENODEV;
        goto out;
}

static int
sg_add(struct class_device *cl_dev)
{
        struct scsi_device *scsidp = to_scsi_device(cl_dev->dev);
        struct gendisk *disk;
        Sg_device *sdp = NULL;
        struct cdev * cdev = NULL;
        int error, k;

        disk = alloc_disk(1);
        if (!disk) {
                printk(KERN_WARNING "alloc_disk failed\n");
                return -ENOMEM;
        }
        disk->major = SCSI_GENERIC_MAJOR;

        error = -ENOMEM;
        cdev = cdev_alloc();
        if (!cdev) {
                printk(KERN_WARNING "cdev_alloc failed\n");
                goto out;
        }
        cdev->owner = THIS_MODULE;
        cdev->ops = &sg_fops;

        error = sg_alloc(disk, scsidp);
        if (error < 0) {
                printk(KERN_WARNING "sg_alloc failed\n");
                goto out;
        }
        k = error;
        sdp = sg_dev_arr[k];

        devfs_mk_cdev(MKDEV(SCSI_GENERIC_MAJOR, k),
                        S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP,
                        "%s/generic", scsidp->devfs_name);
        error = cdev_add(cdev, MKDEV(SCSI_GENERIC_MAJOR, k), 1);
        if (error) {
                devfs_remove("%s/generic", scsidp->devfs_name);
                goto out;
        }
        sdp->cdev = cdev;
        if (sg_sysfs_valid) {
                struct class_device * sg_class_member;

                sg_class_member = class_simple_device_add(sg_sysfs_class, 
                                MKDEV(SCSI_GENERIC_MAJOR, k), 
                                cl_dev->dev, "%s", 
                                disk->disk_name);
                if (IS_ERR(sg_class_member))
                        printk(KERN_WARNING "sg_add: "
                                "class_simple_device_add failed\n");
                class_set_devdata(sg_class_member, sdp);
                error = sysfs_create_link(&scsidp->sdev_gendev.kobj, 
                                          &sg_class_member->kobj, "generic");
                if (error)
                        printk(KERN_ERR "sg_add: unable to make symlink "
                                        "'generic' back to sg%d\n", k);
        } else
                printk(KERN_WARNING "sg_add: sg_sys INvalid\n");

        printk(KERN_NOTICE
               "Attached scsi generic sg%d at scsi%d, channel"
               " %d, id %d, lun %d,  type %d\n", k,
               scsidp->host->host_no, scsidp->channel, scsidp->id,
               scsidp->lun, scsidp->type);

        return 0;

out:
        put_disk(disk);
        if (cdev)
                cdev_del(cdev);
        return error;
}

static void
sg_remove(struct class_device *cl_dev)
{
        struct scsi_device *scsidp = to_scsi_device(cl_dev->dev);
        Sg_device *sdp = NULL;
        unsigned long iflags;
        Sg_fd *sfp;
        Sg_fd *tsfp;
        Sg_request *srp;
        Sg_request *tsrp;
        int k, delay;

        if (NULL == sg_dev_arr)
                return;
        delay = 0;
        write_lock_irqsave(&sg_dev_arr_lock, iflags);
        for (k = 0; k < sg_dev_max; k++) {
                sdp = sg_dev_arr[k];
                if ((NULL == sdp) || (sdp->device != scsidp))
                        continue;       /* dirty but lowers nesting */
                if (sdp->headfp) {
                        sdp->detached = 1;
                        for (sfp = sdp->headfp; sfp; sfp = tsfp) {
                                tsfp = sfp->nextfp;
                                for (srp = sfp->headrp; srp; srp = tsrp) {
                                        tsrp = srp->nextrp;
                                        if (sfp->closed || (0 == sg_srp_done(srp, sfp)))
                                                sg_finish_rem_req(srp);
                                }
                                if (sfp->closed) {
                                        scsi_device_put(sdp->device);
                                        __sg_remove_sfp(sdp, sfp);
                                } else {
                                        delay = 1;
                                        wake_up_interruptible(&sfp->read_wait);
                                        kill_fasync(&sfp->async_qp, SIGPOLL,
                                                    POLL_HUP);
                                }
                        }
                        SCSI_LOG_TIMEOUT(3, printk("sg_detach: dev=%d, dirty\n", k));
                        if (NULL == sdp->headfp) {
                                sg_dev_arr[k] = NULL;
                        }
                } else {        /* nothing active, simple case */
                        SCSI_LOG_TIMEOUT(3, printk("sg_detach: dev=%d\n", k));
                        sg_dev_arr[k] = NULL;
                }
                sg_nr_dev--;
                break;
        }
        write_unlock_irqrestore(&sg_dev_arr_lock, iflags);

        if (sdp) {
                sysfs_remove_link(&scsidp->sdev_gendev.kobj, "generic");
                class_simple_device_remove(MKDEV(SCSI_GENERIC_MAJOR, k));
                cdev_del(sdp->cdev);
                sdp->cdev = NULL;
                devfs_remove("%s/generic", scsidp->devfs_name);
                put_disk(sdp->disk);
                sdp->disk = NULL;
                if (NULL == sdp->headfp)
                        kfree((char *) sdp);
        }

        if (delay)
                msleep(10);     /* dirty detach so delay device destruction */
}

/* Set 'perm' (4th argument) to 0 to disable module_param's definition
 * of sysfs parameters (which module_param doesn't yet support).
 * Sysfs parameters defined explicitly below.
 */
module_param_named(def_reserved_size, def_reserved_size, int, S_IRUGO);
module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR);

MODULE_AUTHOR("Douglas Gilbert");
MODULE_DESCRIPTION("SCSI generic (sg) driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(SG_VERSION_STR);

MODULE_PARM_DESC(def_reserved_size, "size of buffer reserved for each fd");
MODULE_PARM_DESC(allow_dio, "allow direct I/O (default: 0 (disallow))");

static int __init
init_sg(void)
{
        int rc;

        if (def_reserved_size >= 0)
                sg_big_buff = def_reserved_size;

        rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), 
                                    SG_MAX_DEVS, "sg");
        if (rc)
                return rc;
        sg_sysfs_class = class_simple_create(THIS_MODULE, "scsi_generic");
        if ( IS_ERR(sg_sysfs_class) ) {
                rc = PTR_ERR(sg_sysfs_class);
                goto err_out;
        }
        sg_sysfs_valid = 1;
        rc = scsi_register_interface(&sg_interface);
        if (0 == rc) {
#ifdef CONFIG_SCSI_PROC_FS
                sg_proc_init();
#endif                          /* CONFIG_SCSI_PROC_FS */
                return 0;
        }
        class_simple_destroy(sg_sysfs_class);
err_out:
        unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), SG_MAX_DEVS);
        return rc;
}

static void __exit
exit_sg(void)
{
#ifdef CONFIG_SCSI_PROC_FS
        sg_proc_cleanup();
#endif                          /* CONFIG_SCSI_PROC_FS */
        scsi_unregister_interface(&sg_interface);
        class_simple_destroy(sg_sysfs_class);
        sg_sysfs_valid = 0;
        unregister_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
                                 SG_MAX_DEVS);
        if (sg_dev_arr != NULL) {
                kfree((char *) sg_dev_arr);
                sg_dev_arr = NULL;
        }
        sg_dev_max = 0;
}

static int
sg_start_req(Sg_request * srp)
{
        int res;
        Sg_fd *sfp = srp->parentfp;
        sg_io_hdr_t *hp = &srp->header;
        int dxfer_len = (int) hp->dxfer_len;
        int dxfer_dir = hp->dxfer_direction;
        Sg_scatter_hold *req_schp = &srp->data;
        Sg_scatter_hold *rsv_schp = &sfp->reserve;

        SCSI_LOG_TIMEOUT(4, printk("sg_start_req: dxfer_len=%d\n", dxfer_len));
        if ((dxfer_len <= 0) || (dxfer_dir == SG_DXFER_NONE))
                return 0;
        if (sg_allow_dio && (hp->flags & SG_FLAG_DIRECT_IO) &&
            (dxfer_dir != SG_DXFER_UNKNOWN) && (0 == hp->iovec_count) &&
            (!sfp->parentdp->device->host->unchecked_isa_dma)) {
                res = sg_build_direct(srp, sfp, dxfer_len);
                if (res <= 0)   /* -ve -> error, 0 -> done, 1 -> try indirect */
                        return res;
        }
        if ((!sg_res_in_use(sfp)) && (dxfer_len <= rsv_schp->bufflen))
                sg_link_reserve(sfp, srp, dxfer_len);
        else {
                res = sg_build_indirect(req_schp, sfp, dxfer_len);
                if (res) {
                        sg_remove_scat(req_schp);
                        return res;
                }
        }
        return 0;
}

static void
sg_finish_rem_req(Sg_request * srp)
{
        Sg_fd *sfp = srp->parentfp;
        Sg_scatter_hold *req_schp = &srp->data;

        SCSI_LOG_TIMEOUT(4, printk("sg_finish_rem_req: res_used=%d\n", (int) srp->res_used));
        if (srp->res_used)
                sg_unlink_reserve(sfp, srp);
        else
                sg_remove_scat(req_schp);
        sg_remove_request(sfp, srp);
}

static int
sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
{
        int ret_sz;
        int elem_sz = sizeof (struct scatterlist);
        int sg_bufflen = tablesize * elem_sz;
        int mx_sc_elems = tablesize;

        schp->buffer = sg_page_malloc(sg_bufflen, sfp->low_dma, &ret_sz);
        if (!schp->buffer)
                return -ENOMEM;
        else if (ret_sz != sg_bufflen) {
                sg_bufflen = ret_sz;
                mx_sc_elems = sg_bufflen / elem_sz;
        }
        schp->sglist_len = sg_bufflen;
        memset(schp->buffer, 0, sg_bufflen);
        return mx_sc_elems;     /* number of scat_gath elements allocated */
}

#ifdef SG_ALLOW_DIO_CODE
/* vvvvvvvv  following code borrowed from st driver's direct IO vvvvvvvvv */
        /* hopefully this generic code will moved to a library */

/* Pin down user pages and put them into a scatter gather list. Returns <= 0 if
   - mapping of all pages not successful
   - any page is above max_pfn
   (i.e., either completely successful or fails)
*/
static int 
st_map_user_pages(struct scatterlist *sgl, const unsigned int max_pages, 
                  unsigned long uaddr, size_t count, int rw,
                  unsigned long max_pfn)
{
        int res, i, j;
        unsigned int nr_pages;
        struct page **pages;

        nr_pages = ((uaddr & ~PAGE_MASK) + count + ~PAGE_MASK) >> PAGE_SHIFT;

        /* User attempted Overflow! */
        if ((uaddr + count) < uaddr)
                return -EINVAL;

        /* Too big */
        if (nr_pages > max_pages)
                return -ENOMEM;

        /* Hmm? */
        if (count == 0)
                return 0;

        if ((pages = kmalloc(max_pages * sizeof(*pages), GFP_ATOMIC)) == NULL)
                return -ENOMEM;

        /* Try to fault in all of the necessary pages */
        down_read(&current->mm->mmap_sem);
        /* rw==READ means read from drive, write into memory area */
        res = get_user_pages(
                current,
                current->mm,
                uaddr,
                nr_pages,
                rw == READ,
                0, /* don't force */
                pages,
                NULL);
        up_read(&current->mm->mmap_sem);

        /* Errors and no page mapped should return here */
        if (res < nr_pages)
                goto out_unmap;

        for (i=0; i < nr_pages; i++) {
                /* FIXME: flush superflous for rw==READ,
                 * probably wrong function for rw==WRITE
                 */
                flush_dcache_page(pages[i]);
                if (page_to_pfn(pages[i]) > max_pfn)
                        goto out_unlock;
                /* ?? Is locking needed? I don't think so */
                /* if (TestSetPageLocked(pages[i]))
                   goto out_unlock; */
        }

        /* Populate the scatter/gather list */
        sgl[0].page = pages[0]; 
        sgl[0].offset = uaddr & ~PAGE_MASK;
        if (nr_pages > 1) {
                sgl[0].length = PAGE_SIZE - sgl[0].offset;
                count -= sgl[0].length;
                for (i=1; i < nr_pages ; i++) {
                        sgl[i].offset = 0;
                        sgl[i].page = pages[i]; 
                        sgl[i].length = count < PAGE_SIZE ? count : PAGE_SIZE;
                        count -= PAGE_SIZE;
                }
        }
        else {
                sgl[0].length = count;
        }

        kfree(pages);
        return nr_pages;

 out_unlock:
        /* for (j=0; j < i; j++)
           unlock_page(pages[j]); */
        res = 0;
 out_unmap:
        if (res > 0)
                for (j=0; j < res; j++)
                        page_cache_release(pages[j]);
        kfree(pages);
        return res;
}


/* And unmap them... */
static int 
st_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages,
                    int dirtied)
{
        int i;

        for (i=0; i < nr_pages; i++) {
                if (dirtied && !PageReserved(sgl[i].page))
                        SetPageDirty(sgl[i].page);
                /* unlock_page(sgl[i].page); */
                /* FIXME: cache flush missing for rw==READ
                 * FIXME: call the correct reference counting function
                 */
                page_cache_release(sgl[i].page);
        }

        return 0;
}

/* ^^^^^^^^  above code borrowed from st driver's direct IO ^^^^^^^^^ */
#endif


/* Returns: -ve -> error, 0 -> done, 1 -> try indirect */
static int
sg_build_direct(Sg_request * srp, Sg_fd * sfp, int dxfer_len)
{
#ifdef SG_ALLOW_DIO_CODE
        sg_io_hdr_t *hp = &srp->header;
        Sg_scatter_hold *schp = &srp->data;
        int sg_tablesize = sfp->parentdp->sg_tablesize;
        struct scatterlist *sgl;
        int mx_sc_elems, res;
        struct scsi_device *sdev = sfp->parentdp->device;

        if (((unsigned long)hp->dxferp &
                        queue_dma_alignment(sdev->request_queue)) != 0)
                return 1;
        mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
        if (mx_sc_elems <= 0) {
                return 1;
        }
        sgl = (struct scatterlist *)schp->buffer;
        res = st_map_user_pages(sgl, mx_sc_elems, (unsigned long)hp->dxferp, dxfer_len, 
                                (SG_DXFER_TO_DEV == hp->dxfer_direction) ? 1 : 0, ULONG_MAX);
        if (res <= 0)
                return 1;
        schp->k_use_sg = res;
        schp->dio_in_use = 1;
        hp->info |= SG_INFO_DIRECT_IO;
        return 0;
#else
        return 1;
#endif
}

static int
sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
{
        int ret_sz;
        int blk_size = buff_size;
        unsigned char *p = NULL;

        if ((blk_size < 0) || (!sfp))
                return -EFAULT;
        if (0 == blk_size)
                ++blk_size;     /* don't know why */
/* round request up to next highest SG_SECTOR_SZ byte boundary */
        blk_size = (blk_size + SG_SECTOR_MSK) & (~SG_SECTOR_MSK);
        SCSI_LOG_TIMEOUT(4, printk("sg_build_indirect: buff_size=%d, blk_size=%d\n",
                                   buff_size, blk_size));
        if (blk_size <= SG_SCATTER_SZ) {
                p = sg_page_malloc(blk_size, sfp->low_dma, &ret_sz);
                if (!p)
                        return -ENOMEM;
                if (blk_size == ret_sz) {       /* got it on the first attempt */
                        schp->k_use_sg = 0;
                        schp->buffer = p;
                        schp->bufflen = blk_size;
                        schp->b_malloc_len = blk_size;
                        return 0;
                }
        } else {
                p = sg_page_malloc(SG_SCATTER_SZ, sfp->low_dma, &ret_sz);
                if (!p)
                        return -ENOMEM;
        }
/* Want some local declarations, so start new block ... */
        {                       /* lets try and build a scatter gather list */
                struct scatterlist *sclp;
                int k, rem_sz, num;
                int mx_sc_elems;
                int sg_tablesize = sfp->parentdp->sg_tablesize;
                int first = 1;

                /* N.B. ret_sz carried into this block ... */
                mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
                if (mx_sc_elems < 0)
                        return mx_sc_elems;     /* most likely -ENOMEM */

                for (k = 0, sclp = schp->buffer, rem_sz = blk_size;
                     (rem_sz > 0) && (k < mx_sc_elems);
                     ++k, rem_sz -= ret_sz, ++sclp) {
                        if (first)
                                first = 0;
                        else {
                                num =
                                    (rem_sz >
                                     SG_SCATTER_SZ) ? SG_SCATTER_SZ : rem_sz;
                                p = sg_page_malloc(num, sfp->low_dma, &ret_sz);
                                if (!p)
                                        break;
                        }
                        sclp->page = virt_to_page(p);
                        sclp->offset = offset_in_page(p);
                        sclp->length = ret_sz;

                        SCSI_LOG_TIMEOUT(5, printk("sg_build_build: k=%d, a=0x%p, len=%d\n",
                                          k, sg_scatg2virt(sclp), ret_sz));
                }               /* end of for loop */
                schp->k_use_sg = k;
                SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k_use_sg=%d, rem_sz=%d\n", k, rem_sz));
                schp->bufflen = blk_size;
                if (rem_sz > 0) /* must have failed */
                        return -ENOMEM;
        }
        return 0;
}

static int
sg_write_xfer(Sg_request * srp)
{
        sg_io_hdr_t *hp = &srp->header;
        Sg_scatter_hold *schp = &srp->data;
        int num_xfer = 0;
        int j, k, onum, usglen, ksglen, res;
        int iovec_count = (int) hp->iovec_count;
        int dxfer_dir = hp->dxfer_direction;
        unsigned char *p;
        unsigned char __user *up;
        int new_interface = ('\0' == hp->interface_id) ? 0 : 1;

        if ((SG_DXFER_UNKNOWN == dxfer_dir) || (SG_DXFER_TO_DEV == dxfer_dir) ||
            (SG_DXFER_TO_FROM_DEV == dxfer_dir)) {
                num_xfer = (int) (new_interface ? hp->dxfer_len : hp->flags);
                if (schp->bufflen < num_xfer)
                        num_xfer = schp->bufflen;
        }
        if ((num_xfer <= 0) || (schp->dio_in_use) ||
            (new_interface
             && ((SG_FLAG_NO_DXFER | SG_FLAG_MMAP_IO) & hp->flags)))
                return 0;

        SCSI_LOG_TIMEOUT(4, printk("sg_write_xfer: num_xfer=%d, iovec_count=%d, k_use_sg=%d\n",
                          num_xfer, iovec_count, schp->k_use_sg));
        if (iovec_count) {
                onum = iovec_count;
                if ((k = verify_area(VERIFY_READ, hp->dxferp,
                                     SZ_SG_IOVEC * onum)))
                        return k;
        } else
                onum = 1;

        if (0 == schp->k_use_sg) {      /* kernel has single buffer */
                for (j = 0, p = schp->buffer; j < onum; ++j) {
                        res = sg_u_iovec(hp, iovec_count, j, 1, &usglen, &up);
                        if (res)
                                return res;
                        usglen = (num_xfer > usglen) ? usglen : num_xfer;
                        if (__copy_from_user(p, up, usglen))
                                return -EFAULT;
                        p += usglen;
                        num_xfer -= usglen;
                        if (num_xfer <= 0)
                                return 0;
                }
        } else {                /* kernel using scatter gather list */
                struct scatterlist *sclp = (struct scatterlist *) schp->buffer;

                ksglen = (int) sclp->length;
                p = sg_scatg2virt(sclp);
                for (j = 0, k = 0; j < onum; ++j) {
                        res = sg_u_iovec(hp, iovec_count, j, 1, &usglen, &up);
                        if (res)
                                return res;

                        for (; p; ++sclp, ksglen = (int) sclp->length,
                                  p = sg_scatg2virt(sclp)) {
                                if (usglen <= 0)
                                        break;
                                if (ksglen > usglen) {
                                        if (usglen >= num_xfer) {
                                                if (__copy_from_user
                                                    (p, up, num_xfer))
                                                        return -EFAULT;
                                                return 0;

                                        }
                                        if (__copy_from_user(p, up, usglen))
                                                return -EFAULT;
                                        p += usglen;
                                        ksglen -= usglen;
                                        break;
                                } else {
                                        if (ksglen >= num_xfer) {
                                                if (__copy_from_user
                                                    (p, up, num_xfer))
                                                        return -EFAULT;
                                                return 0;
                                        }
                                        if (__copy_from_user(p, up, ksglen))
                                                return -EFAULT;
                                        up += ksglen;
                                        usglen -= ksglen;
                                }
                                ++k;
                                if (k >= schp->k_use_sg)
                                        return 0;
                        }
                }
        }
        return 0;
}

static int
sg_u_iovec(sg_io_hdr_t * hp, int sg_num, int ind,
           int wr_xf, int *countp, unsigned char __user **up)
{
        int num_xfer = (int) hp->dxfer_len;
        unsigned char __user *p = hp->dxferp;
        int count, k;

        if (0 == sg_num) {
                if (wr_xf && ('\0' == hp->interface_id))
                        count = (int) hp->flags;        /* holds "old" input_size */
                else
                        count = num_xfer;
        } else {
                sg_iovec_t iovec;
                if (__copy_from_user(&iovec, p + ind*SZ_SG_IOVEC, SZ_SG_IOVEC))
                        return -EFAULT;
                p = iovec.iov_base;
                count = (int) iovec.iov_len;
        }
        if ((k = verify_area(wr_xf ? VERIFY_READ : VERIFY_WRITE, p, count)))
                return k;
        if (up)
                *up = p;
        if (countp)
                *countp = count;
        return 0;
}

static void
sg_remove_scat(Sg_scatter_hold * schp)
{
        SCSI_LOG_TIMEOUT(4, printk("sg_remove_scat: k_use_sg=%d\n", schp->k_use_sg));
        if (schp->buffer && (schp->sglist_len > 0)) {
                struct scatterlist *sclp = (struct scatterlist *) schp->buffer;

                if (schp->dio_in_use) {
#ifdef SG_ALLOW_DIO_CODE
                        st_unmap_user_pages(sclp, schp->k_use_sg, TRUE);
#endif
                } else {
                        int k;

                        for (k = 0; (k < schp->k_use_sg) && sg_scatg2virt(sclp);
                             ++k, ++sclp) {
                                SCSI_LOG_TIMEOUT(5, printk(
                                    "sg_remove_scat: k=%d, a=0x%p, len=%d\n",
                                    k, sg_scatg2virt(sclp), sclp->length));
                                sg_page_free(sg_scatg2virt(sclp), sclp->length);
                                sclp->page = NULL;
                                sclp->offset = 0;
                                sclp->length = 0;
                        }
                }
                sg_page_free(schp->buffer, schp->sglist_len);
        } else if (schp->buffer)
                sg_page_free(schp->buffer, schp->b_malloc_len);
        memset(schp, 0, sizeof (*schp));
}

static int
sg_read_xfer(Sg_request * srp)
{
        sg_io_hdr_t *hp = &srp->header;
        Sg_scatter_hold *schp = &srp->data;
        int num_xfer = 0;
        int j, k, onum, usglen, ksglen, res;
        int iovec_count = (int) hp->iovec_count;
        int dxfer_dir = hp->dxfer_direction;
        unsigned char *p;
        unsigned char __user *up;
        int new_interface = ('\0' == hp->interface_id) ? 0 : 1;

        if ((SG_DXFER_UNKNOWN == dxfer_dir) || (SG_DXFER_FROM_DEV == dxfer_dir)
            || (SG_DXFER_TO_FROM_DEV == dxfer_dir)) {
                num_xfer = hp->dxfer_len;
                if (schp->bufflen < num_xfer)
                        num_xfer = schp->bufflen;
        }
        if ((num_xfer <= 0) || (schp->dio_in_use) ||
            (new_interface
             && ((SG_FLAG_NO_DXFER | SG_FLAG_MMAP_IO) & hp->flags)))
                return 0;

        SCSI_LOG_TIMEOUT(4, printk("sg_read_xfer: num_xfer=%d, iovec_count=%d, k_use_sg=%d\n",
                          num_xfer, iovec_count, schp->k_use_sg));
        if (iovec_count) {
                onum = iovec_count;
                if ((k = verify_area(VERIFY_READ, hp->dxferp,
                                     SZ_SG_IOVEC * onum)))
                        return k;
        } else
                onum = 1;

        if (0 == schp->k_use_sg) {      /* kernel has single buffer */
                for (j = 0, p = schp->buffer; j < onum; ++j) {
                        res = sg_u_iovec(hp, iovec_count, j, 0, &usglen, &up);
                        if (res)
                                return res;
                        usglen = (num_xfer > usglen) ? usglen : num_xfer;
                        if (__copy_to_user(up, p, usglen))
                                return -EFAULT;
                        p += usglen;
                        num_xfer -= usglen;
                        if (num_xfer <= 0)
                                return 0;
                }
        } else {                /* kernel using scatter gather list */
                struct scatterlist *sclp = (struct scatterlist *) schp->buffer;

                ksglen = (int) sclp->length;
                p = sg_scatg2virt(sclp);
                for (j = 0, k = 0; j < onum; ++j) {
                        res = sg_u_iovec(hp, iovec_count, j, 0, &usglen, &up);
                        if (res)
                                return res;

                        for (; p; ++sclp, ksglen = (int) sclp->length,
                                  p = sg_scatg2virt(sclp)) {
                                if (usglen <= 0)
                                        break;
                                if (ksglen > usglen) {
                                        if (usglen >= num_xfer) {
                                                if (__copy_to_user
                                                    (up, p, num_xfer))
                                                        return -EFAULT;
                                                return 0;
                                        }
                                        if (__copy_to_user(up, p, usglen))
                                                return -EFAULT;
                                        p += usglen;
                                        ksglen -= usglen;
                                        break;
                                } else {
                                        if (ksglen >= num_xfer) {
                                                if (__copy_to_user
                                                    (up, p, num_xfer))
                                                        return -EFAULT;
                                                return 0;
                                        }
                                        if (__copy_to_user(up, p, ksglen))
                                                return -EFAULT;
                                        up += ksglen;
                                        usglen -= ksglen;
                                }
                                ++k;
                                if (k >= schp->k_use_sg)
                                        return 0;
                        }
                }
        }
        return 0;
}

static int
sg_read_oxfer(Sg_request * srp, char __user *outp, int num_read_xfer)
{
        Sg_scatter_hold *schp = &srp->data;

        SCSI_LOG_TIMEOUT(4, printk("sg_read_oxfer: num_read_xfer=%d\n",
                                   num_read_xfer));
        if ((!outp) || (num_read_xfer <= 0))
                return 0;
        if (schp->k_use_sg > 0) {
                int k, num;
                struct scatterlist *sclp = (struct scatterlist *) schp->buffer;

                for (k = 0; (k < schp->k_use_sg) && sg_scatg2virt(sclp);
                     ++k, ++sclp) {
                        num = (int) sclp->length;
                        if (num > num_read_xfer) {
                                if (__copy_to_user
                                    (outp, sg_scatg2virt(sclp), num_read_xfer))
                                        return -EFAULT;
                                break;
                        } else {
                                if (__copy_to_user
                                    (outp, sg_scatg2virt(sclp), num))
                                        return -EFAULT;
                                num_read_xfer -= num;
                                if (num_read_xfer <= 0)
                                        break;
                                outp += num;
                        }
                }
        } else {
                if (__copy_to_user(outp, schp->buffer, num_read_xfer))
                        return -EFAULT;
        }
        return 0;
}

static void
sg_build_reserve(Sg_fd * sfp, int req_size)
{
        Sg_scatter_hold *schp = &sfp->reserve;

        SCSI_LOG_TIMEOUT(4, printk("sg_build_reserve: req_size=%d\n", req_size));
        do {
                if (req_size < PAGE_SIZE)
                        req_size = PAGE_SIZE;
                if (0 == sg_build_indirect(schp, sfp, req_size))
                        return;
                else
                        sg_remove_scat(schp);
                req_size >>= 1; /* divide by 2 */
        } while (req_size > (PAGE_SIZE / 2));
}

static void
sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size)
{
        Sg_scatter_hold *req_schp = &srp->data;
        Sg_scatter_hold *rsv_schp = &sfp->reserve;

        srp->res_used = 1;
        SCSI_LOG_TIMEOUT(4, printk("sg_link_reserve: size=%d\n", size));
        size = (size + 1) & (~1);       /* round to even for aha1542 */
        if (rsv_schp->k_use_sg > 0) {
                int k, num;
                int rem = size;
                struct scatterlist *sclp =
                    (struct scatterlist *) rsv_schp->buffer;

                for (k = 0; k < rsv_schp->k_use_sg; ++k, ++sclp) {
                        num = (int) sclp->length;
                        if (rem <= num) {
                                if (0 == k) {
                                        req_schp->k_use_sg = 0;
                                        req_schp->buffer = sg_scatg2virt(sclp);
                                } else {
                                        sfp->save_scat_len = num;
                                        sclp->length = (unsigned) rem;
                                        req_schp->k_use_sg = k + 1;
                                        req_schp->sglist_len =
                                            rsv_schp->sglist_len;
                                        req_schp->buffer = rsv_schp->buffer;
                                }
                                req_schp->bufflen = size;
                                req_schp->b_malloc_len = rsv_schp->b_malloc_len;
                                break;
                        } else
                                rem -= num;
                }
                if (k >= rsv_schp->k_use_sg)
                        SCSI_LOG_TIMEOUT(1, printk("sg_link_reserve: BAD size\n"));
        } else {
                req_schp->k_use_sg = 0;
                req_schp->bufflen = size;
                req_schp->buffer = rsv_schp->buffer;
                req_schp->b_malloc_len = rsv_schp->b_malloc_len;
        }
}

static void
sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp)
{
        Sg_scatter_hold *req_schp = &srp->data;
        Sg_scatter_hold *rsv_schp = &sfp->reserve;

        SCSI_LOG_TIMEOUT(4, printk("sg_unlink_reserve: req->k_use_sg=%d\n",
                                   (int) req_schp->k_use_sg));
        if ((rsv_schp->k_use_sg > 0) && (req_schp->k_use_sg > 0)) {
                struct scatterlist *sclp =
                    (struct scatterlist *) rsv_schp->buffer;

                if (sfp->save_scat_len > 0)
                        (sclp + (req_schp->k_use_sg - 1))->length =
                            (unsigned) sfp->save_scat_len;
                else
                        SCSI_LOG_TIMEOUT(1, printk ("sg_unlink_reserve: BAD save_scat_len\n"));
        }
        req_schp->k_use_sg = 0;
        req_schp->bufflen = 0;
        req_schp->buffer = NULL;
        req_schp->sglist_len = 0;
        sfp->save_scat_len = 0;
        srp->res_used = 0;
}

static Sg_request *
sg_get_rq_mark(Sg_fd * sfp, int pack_id)
{
        Sg_request *resp;
        unsigned long iflags;

        write_lock_irqsave(&sfp->rq_list_lock, iflags);
        for (resp = sfp->headrp; resp; resp = resp->nextrp) {
                /* look for requests that are ready + not SG_IO owned */
                if ((1 == resp->done) && (!resp->sg_io_owned) &&
                    ((-1 == pack_id) || (resp->header.pack_id == pack_id))) {
                        resp->done = 2; /* guard against other readers */
                        break;
                }
        }
        write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return resp;
}

#ifdef CONFIG_SCSI_PROC_FS
static Sg_request *
sg_get_nth_request(Sg_fd * sfp, int nth)
{
        Sg_request *resp;
        unsigned long iflags;
        int k;

        read_lock_irqsave(&sfp->rq_list_lock, iflags);
        for (k = 0, resp = sfp->headrp; resp && (k < nth);
             ++k, resp = resp->nextrp) ;
        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return resp;
}
#endif

/* always adds to end of list */
static Sg_request *
sg_add_request(Sg_fd * sfp)
{
        int k;
        unsigned long iflags;
        Sg_request *resp;
        Sg_request *rp = sfp->req_arr;

        write_lock_irqsave(&sfp->rq_list_lock, iflags);
        resp = sfp->headrp;
        if (!resp) {
                memset(rp, 0, sizeof (Sg_request));
                rp->parentfp = sfp;
                resp = rp;
                sfp->headrp = resp;
        } else {
                if (0 == sfp->cmd_q)
                        resp = NULL;    /* command queuing disallowed */
                else {
                        for (k = 0; k < SG_MAX_QUEUE; ++k, ++rp) {
                                if (!rp->parentfp)
                                        break;
                        }
                        if (k < SG_MAX_QUEUE) {
                                memset(rp, 0, sizeof (Sg_request));
                                rp->parentfp = sfp;
                                while (resp->nextrp)
                                        resp = resp->nextrp;
                                resp->nextrp = rp;
                                resp = rp;
                        } else
                                resp = NULL;
                }
        }
        if (resp) {
                resp->nextrp = NULL;
                resp->header.duration = jiffies;
                resp->my_cmdp = NULL;
        }
        write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return resp;
}

/* Return of 1 for found; 0 for not found */
static int
sg_remove_request(Sg_fd * sfp, Sg_request * srp)
{
        Sg_request *prev_rp;
        Sg_request *rp;
        unsigned long iflags;
        int res = 0;

        if ((!sfp) || (!srp) || (!sfp->headrp))
                return res;
        write_lock_irqsave(&sfp->rq_list_lock, iflags);
        prev_rp = sfp->headrp;
        if (srp == prev_rp) {
                sfp->headrp = prev_rp->nextrp;
                prev_rp->parentfp = NULL;
                res = 1;
        } else {
                while ((rp = prev_rp->nextrp)) {
                        if (srp == rp) {
                                prev_rp->nextrp = rp->nextrp;
                                rp->parentfp = NULL;
                                res = 1;
                                break;
                        }
                        prev_rp = rp;
                }
        }
        write_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return res;
}

#ifdef CONFIG_SCSI_PROC_FS
static Sg_fd *
sg_get_nth_sfp(Sg_device * sdp, int nth)
{
        Sg_fd *resp;
        unsigned long iflags;
        int k;

        read_lock_irqsave(&sg_dev_arr_lock, iflags);
        for (k = 0, resp = sdp->headfp; resp && (k < nth);
             ++k, resp = resp->nextfp) ;
        read_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        return resp;
}
#endif

static Sg_fd *
sg_add_sfp(Sg_device * sdp, int dev)
{
        Sg_fd *sfp;
        unsigned long iflags;

        sfp = (Sg_fd *) sg_page_malloc(sizeof (Sg_fd), 0, NULL);
        if (!sfp)
                return NULL;
        memset(sfp, 0, sizeof (Sg_fd));
        init_waitqueue_head(&sfp->read_wait);
        rwlock_init(&sfp->rq_list_lock);

        sfp->timeout = SG_DEFAULT_TIMEOUT;
        sfp->timeout_user = SG_DEFAULT_TIMEOUT_USER;
        sfp->force_packid = SG_DEF_FORCE_PACK_ID;
        sfp->low_dma = (SG_DEF_FORCE_LOW_DMA == 0) ?
            sdp->device->host->unchecked_isa_dma : 1;
        sfp->cmd_q = SG_DEF_COMMAND_Q;
        sfp->keep_orphan = SG_DEF_KEEP_ORPHAN;
        sfp->parentdp = sdp;
        write_lock_irqsave(&sg_dev_arr_lock, iflags);
        if (!sdp->headfp)
                sdp->headfp = sfp;
        else {                  /* add to tail of existing list */
                Sg_fd *pfp = sdp->headfp;
                while (pfp->nextfp)
                        pfp = pfp->nextfp;
                pfp->nextfp = sfp;
        }
        write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp: sfp=0x%p\n", sfp));
        sg_build_reserve(sfp, sg_big_buff);
        SCSI_LOG_TIMEOUT(3, printk("sg_add_sfp:   bufflen=%d, k_use_sg=%d\n",
                           sfp->reserve.bufflen, sfp->reserve.k_use_sg));
        return sfp;
}

static void
__sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
{
        Sg_fd *fp;
        Sg_fd *prev_fp;

        prev_fp = sdp->headfp;
        if (sfp == prev_fp)
                sdp->headfp = prev_fp->nextfp;
        else {
                while ((fp = prev_fp->nextfp)) {
                        if (sfp == fp) {
                                prev_fp->nextfp = fp->nextfp;
                                break;
                        }
                        prev_fp = fp;
                }
        }
        if (sfp->reserve.bufflen > 0) {
                SCSI_LOG_TIMEOUT(6, 
                        printk("__sg_remove_sfp:    bufflen=%d, k_use_sg=%d\n",
                        (int) sfp->reserve.bufflen, (int) sfp->reserve.k_use_sg));
                if (sfp->mmap_called)
                        sg_rb_correct4mmap(&sfp->reserve, 0);   /* undo correction */
                sg_remove_scat(&sfp->reserve);
        }
        sfp->parentdp = NULL;
        SCSI_LOG_TIMEOUT(6, printk("__sg_remove_sfp:    sfp=0x%p\n", sfp));
        sg_page_free((char *) sfp, sizeof (Sg_fd));
}

/* Returns 0 in normal case, 1 when detached and sdp object removed */
static int
sg_remove_sfp(Sg_device * sdp, Sg_fd * sfp)
{
        Sg_request *srp;
        Sg_request *tsrp;
        int dirty = 0;
        int res = 0;

        for (srp = sfp->headrp; srp; srp = tsrp) {
                tsrp = srp->nextrp;
                if (sg_srp_done(srp, sfp))
                        sg_finish_rem_req(srp);
                else
                        ++dirty;
        }
        if (0 == dirty) {
                unsigned long iflags;

                write_lock_irqsave(&sg_dev_arr_lock, iflags);
                __sg_remove_sfp(sdp, sfp);
                if (sdp->detached && (NULL == sdp->headfp)) {
                        int k, maxd;

                        maxd = sg_dev_max;
                        for (k = 0; k < maxd; ++k) {
                                if (sdp == sg_dev_arr[k])
                                        break;
                        }
                        if (k < maxd)
                                sg_dev_arr[k] = NULL;
                        kfree((char *) sdp);
                        res = 1;
                }
                write_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        } else {
                /* MOD_INC's to inhibit unloading sg and associated adapter driver */
                /* only bump the access_count if we actually succeeded in
                 * throwing another counter on the host module */
                scsi_device_get(sdp->device);   /* XXX: retval ignored? */      
                sfp->closed = 1;        /* flag dirty state on this fd */
                SCSI_LOG_TIMEOUT(1, printk("sg_remove_sfp: worrisome, %d writes pending\n",
                                  dirty));
        }
        return res;
}

static int
sg_res_in_use(Sg_fd * sfp)
{
        const Sg_request *srp;
        unsigned long iflags;

        read_lock_irqsave(&sfp->rq_list_lock, iflags);
        for (srp = sfp->headrp; srp; srp = srp->nextrp)
                if (srp->res_used)
                        break;
        read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
        return srp ? 1 : 0;
}

/* If retSzp==NULL want exact size or fail */
static char *
sg_page_malloc(int rqSz, int lowDma, int *retSzp)
{
        char *resp = NULL;
        int page_mask;
        int order, a_size;
        int resSz = rqSz;

        if (rqSz <= 0)
                return resp;

        if (lowDma)
                page_mask = GFP_ATOMIC | GFP_DMA | __GFP_NOWARN;
        else
                page_mask = GFP_ATOMIC | __GFP_NOWARN;

        for (order = 0, a_size = PAGE_SIZE; a_size < rqSz;
             order++, a_size <<= 1) ;
        resp = (char *) __get_free_pages(page_mask, order);
        while ((!resp) && order && retSzp) {
                --order;
                a_size >>= 1;   /* divide by 2, until PAGE_SIZE */
                resp = (char *) __get_free_pages(page_mask, order);     /* try half */
                resSz = a_size;
        }
        if (resp) {
                if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                        memset(resp, 0, resSz);
                if (retSzp)
                        *retSzp = resSz;
        }
        return resp;
}

static void
sg_page_free(char *buff, int size)
{
        int order, a_size;

        if (!buff)
                return;
        for (order = 0, a_size = PAGE_SIZE; a_size < size;
             order++, a_size <<= 1) ;
        free_pages((unsigned long) buff, order);
}

#ifndef MAINTENANCE_IN_CMD
#define MAINTENANCE_IN_CMD 0xa3
#endif

static unsigned char allow_ops[] = { TEST_UNIT_READY, REQUEST_SENSE,
        INQUIRY, READ_CAPACITY, READ_BUFFER, READ_6, READ_10, READ_12,
        READ_16, MODE_SENSE, MODE_SENSE_10, LOG_SENSE, REPORT_LUNS,
        SERVICE_ACTION_IN, RECEIVE_DIAGNOSTIC, READ_LONG, MAINTENANCE_IN_CMD
};

static int
sg_allow_access(unsigned char opcode, char dev_type)
{
        int k;

        if (TYPE_SCANNER == dev_type)   /* TYPE_ROM maybe burner */
                return 1;
        for (k = 0; k < sizeof (allow_ops); ++k) {
                if (opcode == allow_ops[k])
                        return 1;
        }
        return 0;
}

#ifdef CONFIG_SCSI_PROC_FS
static int
sg_last_dev(void)
{
        int k;
        unsigned long iflags;

        read_lock_irqsave(&sg_dev_arr_lock, iflags);
        for (k = sg_dev_max - 1; k >= 0; --k)
                if (sg_dev_arr[k] && sg_dev_arr[k]->device)
                        break;
        read_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        return k + 1;           /* origin 1 */
}
#endif

static Sg_device *
sg_get_dev(int dev)
{
        Sg_device *sdp = NULL;
        unsigned long iflags;

        if (sg_dev_arr && (dev >= 0)) {
                read_lock_irqsave(&sg_dev_arr_lock, iflags);
                if (dev < sg_dev_max)
                        sdp = sg_dev_arr[dev];
                read_unlock_irqrestore(&sg_dev_arr_lock, iflags);
        }
        return sdp;
}

#ifdef CONFIG_SCSI_PROC_FS

static struct proc_dir_entry *sg_proc_sgp = NULL;

static char sg_proc_sg_dirname[] = "scsi/sg";

static int sg_proc_seq_show_int(struct seq_file *s, void *v);

static int sg_proc_single_open_adio(struct inode *inode, struct file *file);
static ssize_t sg_proc_write_adio(struct file *filp, const char __user *buffer,
                                  size_t count, loff_t *off);
static struct file_operations adio_fops = {
        /* .owner, .read and .llseek added in sg_proc_init() */
        .open = sg_proc_single_open_adio,
        .write = sg_proc_write_adio,
        .release = single_release,
};

static int sg_proc_single_open_dressz(struct inode *inode, struct file *file);
static ssize_t sg_proc_write_dressz(struct file *filp, 
                const char __user *buffer, size_t count, loff_t *off);
static struct file_operations dressz_fops = {
        .open = sg_proc_single_open_dressz,
        .write = sg_proc_write_dressz,
        .release = single_release,
};

static int sg_proc_seq_show_version(struct seq_file *s, void *v);
static int sg_proc_single_open_version(struct inode *inode, struct file *file);
static struct file_operations version_fops = {
        .open = sg_proc_single_open_version,
        .release = single_release,
};

static int sg_proc_seq_show_devhdr(struct seq_file *s, void *v);
static int sg_proc_single_open_devhdr(struct inode *inode, struct file *file);
static struct file_operations devhdr_fops = {
        .open = sg_proc_single_open_devhdr,
        .release = single_release,
};

static int sg_proc_seq_show_dev(struct seq_file *s, void *v);
static int sg_proc_open_dev(struct inode *inode, struct file *file);
static void * dev_seq_start(struct seq_file *s, loff_t *pos);
static void * dev_seq_next(struct seq_file *s, void *v, loff_t *pos);
static void dev_seq_stop(struct seq_file *s, void *v);
static struct file_operations dev_fops = {
        .open = sg_proc_open_dev,
        .release = seq_release,
};
static struct seq_operations dev_seq_ops = {
        .start = dev_seq_start,
        .next  = dev_seq_next,
        .stop  = dev_seq_stop,
        .show  = sg_proc_seq_show_dev,
};

static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v);
static int sg_proc_open_devstrs(struct inode *inode, struct file *file);
static struct file_operations devstrs_fops = {
        .open = sg_proc_open_devstrs,
        .release = seq_release,
};
static struct seq_operations devstrs_seq_ops = {
        .start = dev_seq_start,
        .next  = dev_seq_next,
        .stop  = dev_seq_stop,
        .show  = sg_proc_seq_show_devstrs,
};

static int sg_proc_seq_show_debug(struct seq_file *s, void *v);
static int sg_proc_open_debug(struct inode *inode, struct file *file);
static struct file_operations debug_fops = {
        .open = sg_proc_open_debug,
        .release = seq_release,
};
static struct seq_operations debug_seq_ops = {
        .start = dev_seq_start,
        .next  = dev_seq_next,
        .stop  = dev_seq_stop,
        .show  = sg_proc_seq_show_debug,
};


struct sg_proc_leaf {
        const char * name;
        struct file_operations * fops;
};

static struct sg_proc_leaf sg_proc_leaf_arr[] = {
        {"allow_dio", &adio_fops},
        {"debug", &debug_fops},
        {"def_reserved_size", &dressz_fops},
        {"device_hdr", &devhdr_fops},
        {"devices", &dev_fops},
        {"device_strs", &devstrs_fops},
        {"version", &version_fops}
};

static int
sg_proc_init(void)
{
        int k, mask;
        int num_leaves =
            sizeof (sg_proc_leaf_arr) / sizeof (sg_proc_leaf_arr[0]);
        struct proc_dir_entry *pdep;
        struct sg_proc_leaf * leaf;

        sg_proc_sgp = create_proc_entry(sg_proc_sg_dirname,
                                        S_IFDIR | S_IRUGO | S_IXUGO, NULL);
        if (!sg_proc_sgp)
                return 1;
        for (k = 0; k < num_leaves; ++k) {
                leaf = &sg_proc_leaf_arr[k];
                mask = leaf->fops->write ? S_IRUGO | S_IWUSR : S_IRUGO;
                pdep = create_proc_entry(leaf->name, mask, sg_proc_sgp);
                if (pdep) {
                        leaf->fops->owner = THIS_MODULE,
                        leaf->fops->read = seq_read,
                        leaf->fops->llseek = seq_lseek,
                        pdep->proc_fops = leaf->fops;
                }
        }
        return 0;
}

static void
sg_proc_cleanup(void)
{
        int k;
        int num_leaves =
            sizeof (sg_proc_leaf_arr) / sizeof (sg_proc_leaf_arr[0]);

        if (!sg_proc_sgp)
                return;
        for (k = 0; k < num_leaves; ++k)
                remove_proc_entry(sg_proc_leaf_arr[k].name, sg_proc_sgp);
        remove_proc_entry(sg_proc_sg_dirname, NULL);
}


static int sg_proc_seq_show_int(struct seq_file *s, void *v)
{
        seq_printf(s, "%d\n", *((int *)s->private));
        return 0;
}

static int sg_proc_single_open_adio(struct inode *inode, struct file *file)
{
        return single_open(file, sg_proc_seq_show_int, &sg_allow_dio);
}

static ssize_t 
sg_proc_write_adio(struct file *filp, const char __user *buffer,
                   size_t count, loff_t *off)
{
        int num;
        char buff[11];

        if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                return -EACCES;
        num = (count < 10) ? count : 10;
        if (copy_from_user(buff, buffer, num))
                return -EFAULT;
        buff[num] = '\0';
        sg_allow_dio = simple_strtoul(buff, NULL, 10) ? 1 : 0;
        return count;
}

static int sg_proc_single_open_dressz(struct inode *inode, struct file *file)
{
        return single_open(file, sg_proc_seq_show_int, &sg_big_buff);
}

static ssize_t 
sg_proc_write_dressz(struct file *filp, const char __user *buffer,
                     size_t count, loff_t *off)
{
        int num;
        unsigned long k = ULONG_MAX;
        char buff[11];

        if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
                return -EACCES;
        num = (count < 10) ? count : 10;
        if (copy_from_user(buff, buffer, num))
                return -EFAULT;
        buff[num] = '\0';
        k = simple_strtoul(buff, NULL, 10);
        if (k <= 1048576) {     /* limit "big buff" to 1 MB */
                sg_big_buff = k;
                return count;
        }
        return -ERANGE;
}

static int sg_proc_seq_show_version(struct seq_file *s, void *v)
{
        seq_printf(s, "%d\t%s [%s]\n", sg_version_num, SG_VERSION_STR,
                   sg_version_date);
        return 0;
}

static int sg_proc_single_open_version(struct inode *inode, struct file *file)
{
        return single_open(file, sg_proc_seq_show_version, NULL);
}

static int sg_proc_seq_show_devhdr(struct seq_file *s, void *v)
{
        seq_printf(s, "host\tchan\tid\tlun\ttype\topens\tqdepth\tbusy\t"
                   "online\n");
        return 0;
}

static int sg_proc_single_open_devhdr(struct inode *inode, struct file *file)
{
        return single_open(file, sg_proc_seq_show_devhdr, NULL);
}

struct sg_proc_deviter {
        loff_t  index;
        size_t  max;
};

static void * dev_seq_start(struct seq_file *s, loff_t *pos)
{
        struct sg_proc_deviter * it = kmalloc(sizeof(*it), GFP_KERNEL);

        if (! it)
                return NULL;
        if (NULL == sg_dev_arr)
                goto err1;
        it->index = *pos;
        it->max = sg_last_dev();
        if (it->index >= it->max)
                goto err1;
        return it;
err1:
        kfree(it);
        return NULL;
}

static void * dev_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
        struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;

        *pos = ++it->index;
        return (it->index < it->max) ? it : NULL;
}

static void dev_seq_stop(struct seq_file *s, void *v)
{
        kfree (v);
}

static int sg_proc_open_dev(struct inode *inode, struct file *file)
{
        return seq_open(file, &dev_seq_ops);
}

static int sg_proc_seq_show_dev(struct seq_file *s, void *v)
{
        struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
        Sg_device *sdp;
        struct scsi_device *scsidp;

        sdp = it ? sg_get_dev(it->index) : NULL;
        if (sdp && (scsidp = sdp->device) && (!sdp->detached))
                seq_printf(s, "%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d\n",
                              scsidp->host->host_no, scsidp->channel,
                              scsidp->id, scsidp->lun, (int) scsidp->type,
                              1,
                              (int) scsidp->queue_depth,
                              (int) scsidp->device_busy,
                              (int) scsi_device_online(scsidp));
        else
                seq_printf(s, "-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\t-1\n");
        return 0;
}

static int sg_proc_open_devstrs(struct inode *inode, struct file *file)
{
        return seq_open(file, &devstrs_seq_ops);
}

static int sg_proc_seq_show_devstrs(struct seq_file *s, void *v)
{
        struct sg_proc_deviter * it = (struct sg_proc_deviter *) v;
        Sg_device *sdp;
        struct scsi_device *scsidp;

        sdp = it ? sg_get_dev(it->index) : NULL;
        if (sdp && (scsidp = sdp->device) && (!sdp->detached))
                seq_printf(s, "%8.8s\t%16.16s\t%4.4s\n",
                           scsidp->vendor, scsidp->model, scsidp->rev);
        else
                seq_printf(s, "<no active device>\n");
        return 0;
}

static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
{
        int k, m, new_interface, blen, usg;
        Sg_request *srp;
        Sg_fd *fp;
        const sg_io_hdr_t *hp;
        const char * cp;

        for (k = 0; (fp = sg_get_nth_sfp(sdp, k)); ++k) {
                seq_printf(s, "   FD(%d): timeout=%dms bufflen=%d "
                           "(res)sgat=%d low_dma=%d\n", k + 1,
                           jiffies_to_msecs(fp->timeout),
                           fp->reserve.bufflen,
                           (int) fp->reserve.k_use_sg,
                           (int) fp->low_dma);
                seq_printf(s, "   cmd_q=%d f_packid=%d k_orphan=%d closed=%d\n",
                           (int) fp->cmd_q, (int) fp->force_packid,
                           (int) fp->keep_orphan, (int) fp->closed);
                for (m = 0; (srp = sg_get_nth_request(fp, m)); ++m) {
                        hp = &srp->header;
                        new_interface = (hp->interface_id == '\0') ? 0 : 1;
                        if (srp->res_used) {
                                if (new_interface && 
                                    (SG_FLAG_MMAP_IO & hp->flags))
                                        cp = "     mmap>> ";
                                else
                                        cp = "     rb>> ";
                        } else {
                                if (SG_INFO_DIRECT_IO_MASK & hp->info)
                                        cp = "     dio>> ";
                                else
                                        cp = "     ";
                        }