linux/drivers/usb/usb-skeleton.c
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   1/*
   2 * USB Skeleton driver - 2.2
   3 *
   4 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
   5 *
   6 *      This program is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU General Public License as
   8 *      published by the Free Software Foundation, version 2.
   9 *
  10 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
  11 * but has been rewritten to be easier to read and use.
  12 *
  13 */
  14
  15#include <linux/kernel.h>
  16#include <linux/errno.h>
  17#include <linux/init.h>
  18#include <linux/slab.h>
  19#include <linux/module.h>
  20#include <linux/kref.h>
  21#include <linux/uaccess.h>
  22#include <linux/usb.h>
  23#include <linux/mutex.h>
  24
  25
  26/* Define these values to match your devices */
  27#define USB_SKEL_VENDOR_ID      0xfff0
  28#define USB_SKEL_PRODUCT_ID     0xfff0
  29
  30/* table of devices that work with this driver */
  31static const struct usb_device_id skel_table[] = {
  32        { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
  33        { }                                     /* Terminating entry */
  34};
  35MODULE_DEVICE_TABLE(usb, skel_table);
  36
  37
  38/* Get a minor range for your devices from the usb maintainer */
  39#define USB_SKEL_MINOR_BASE     192
  40
  41/* our private defines. if this grows any larger, use your own .h file */
  42#define MAX_TRANSFER            (PAGE_SIZE - 512)
  43/* MAX_TRANSFER is chosen so that the VM is not stressed by
  44   allocations > PAGE_SIZE and the number of packets in a page
  45   is an integer 512 is the largest possible packet on EHCI */
  46#define WRITES_IN_FLIGHT        8
  47/* arbitrarily chosen */
  48
  49/* Structure to hold all of our device specific stuff */
  50struct usb_skel {
  51        struct usb_device       *udev;                  /* the usb device for this device */
  52        struct usb_interface    *interface;             /* the interface for this device */
  53        struct semaphore        limit_sem;              /* limiting the number of writes in progress */
  54        struct usb_anchor       submitted;              /* in case we need to retract our submissions */
  55        struct urb              *bulk_in_urb;           /* the urb to read data with */
  56        unsigned char           *bulk_in_buffer;        /* the buffer to receive data */
  57        size_t                  bulk_in_size;           /* the size of the receive buffer */
  58        size_t                  bulk_in_filled;         /* number of bytes in the buffer */
  59        size_t                  bulk_in_copied;         /* already copied to user space */
  60        __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
  61        __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
  62        int                     errors;                 /* the last request tanked */
  63        bool                    ongoing_read;           /* a read is going on */
  64        bool                    processed_urb;          /* indicates we haven't processed the urb */
  65        spinlock_t              err_lock;               /* lock for errors */
  66        struct kref             kref;
  67        struct mutex            io_mutex;               /* synchronize I/O with disconnect */
  68        struct completion       bulk_in_completion;     /* to wait for an ongoing read */
  69};
  70#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
  71
  72static struct usb_driver skel_driver;
  73static void skel_draw_down(struct usb_skel *dev);
  74
  75static void skel_delete(struct kref *kref)
  76{
  77        struct usb_skel *dev = to_skel_dev(kref);
  78
  79        usb_free_urb(dev->bulk_in_urb);
  80        usb_put_dev(dev->udev);
  81        kfree(dev->bulk_in_buffer);
  82        kfree(dev);
  83}
  84
  85static int skel_open(struct inode *inode, struct file *file)
  86{
  87        struct usb_skel *dev;
  88        struct usb_interface *interface;
  89        int subminor;
  90        int retval = 0;
  91
  92        subminor = iminor(inode);
  93
  94        interface = usb_find_interface(&skel_driver, subminor);
  95        if (!interface) {
  96                pr_err("%s - error, can't find device for minor %d\n",
  97                        __func__, subminor);
  98                retval = -ENODEV;
  99                goto exit;
 100        }
 101
 102        dev = usb_get_intfdata(interface);
 103        if (!dev) {
 104                retval = -ENODEV;
 105                goto exit;
 106        }
 107
 108        /* increment our usage count for the device */
 109        kref_get(&dev->kref);
 110
 111        /* lock the device to allow correctly handling errors
 112         * in resumption */
 113        mutex_lock(&dev->io_mutex);
 114
 115        retval = usb_autopm_get_interface(interface);
 116        if (retval)
 117                goto out_err;
 118
 119        /* save our object in the file's private structure */
 120        file->private_data = dev;
 121        mutex_unlock(&dev->io_mutex);
 122
 123exit:
 124        return retval;
 125}
 126
 127static int skel_release(struct inode *inode, struct file *file)
 128{
 129        struct usb_skel *dev;
 130
 131        dev = file->private_data;
 132        if (dev == NULL)
 133                return -ENODEV;
 134
 135        /* allow the device to be autosuspended */
 136        mutex_lock(&dev->io_mutex);
 137        if (dev->interface)
 138                usb_autopm_put_interface(dev->interface);
 139        mutex_unlock(&dev->io_mutex);
 140
 141        /* decrement the count on our device */
 142        kref_put(&dev->kref, skel_delete);
 143        return 0;
 144}
 145
 146static int skel_flush(struct file *file, fl_owner_t id)
 147{
 148        struct usb_skel *dev;
 149        int res;
 150
 151        dev = file->private_data;
 152        if (dev == NULL)
 153                return -ENODEV;
 154
 155        /* wait for io to stop */
 156        mutex_lock(&dev->io_mutex);
 157        skel_draw_down(dev);
 158
 159        /* read out errors, leave subsequent opens a clean slate */
 160        spin_lock_irq(&dev->err_lock);
 161        res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
 162        dev->errors = 0;
 163        spin_unlock_irq(&dev->err_lock);
 164
 165        mutex_unlock(&dev->io_mutex);
 166
 167        return res;
 168}
 169
 170static void skel_read_bulk_callback(struct urb *urb)
 171{
 172        struct usb_skel *dev;
 173
 174        dev = urb->context;
 175
 176        spin_lock(&dev->err_lock);
 177        /* sync/async unlink faults aren't errors */
 178        if (urb->status) {
 179                if (!(urb->status == -ENOENT ||
 180                    urb->status == -ECONNRESET ||
 181                    urb->status == -ESHUTDOWN))
 182                        dev_err(&dev->interface->dev,
 183                                "%s - nonzero write bulk status received: %d\n",
 184                                __func__, urb->status);
 185
 186                dev->errors = urb->status;
 187        } else {
 188                dev->bulk_in_filled = urb->actual_length;
 189        }
 190        dev->ongoing_read = 0;
 191        spin_unlock(&dev->err_lock);
 192
 193        complete(&dev->bulk_in_completion);
 194}
 195
 196static int skel_do_read_io(struct usb_skel *dev, size_t count)
 197{
 198        int rv;
 199
 200        /* prepare a read */
 201        usb_fill_bulk_urb(dev->bulk_in_urb,
 202                        dev->udev,
 203                        usb_rcvbulkpipe(dev->udev,
 204                                dev->bulk_in_endpointAddr),
 205                        dev->bulk_in_buffer,
 206                        min(dev->bulk_in_size, count),
 207                        skel_read_bulk_callback,
 208                        dev);
 209        /* tell everybody to leave the URB alone */
 210        spin_lock_irq(&dev->err_lock);
 211        dev->ongoing_read = 1;
 212        spin_unlock_irq(&dev->err_lock);
 213
 214        /* do it */
 215        rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
 216        if (rv < 0) {
 217                dev_err(&dev->interface->dev,
 218                        "%s - failed submitting read urb, error %d\n",
 219                        __func__, rv);
 220                dev->bulk_in_filled = 0;
 221                rv = (rv == -ENOMEM) ? rv : -EIO;
 222                spin_lock_irq(&dev->err_lock);
 223                dev->ongoing_read = 0;
 224                spin_unlock_irq(&dev->err_lock);
 225        }
 226
 227        return rv;
 228}
 229
 230static ssize_t skel_read(struct file *file, char *buffer, size_t count,
 231                         loff_t *ppos)
 232{
 233        struct usb_skel *dev;
 234        int rv;
 235        bool ongoing_io;
 236
 237        dev = file->private_data;
 238
 239        /* if we cannot read at all, return EOF */
 240        if (!dev->bulk_in_urb || !count)
 241                return 0;
 242
 243        /* no concurrent readers */
 244        rv = mutex_lock_interruptible(&dev->io_mutex);
 245        if (rv < 0)
 246                return rv;
 247
 248        if (!dev->interface) {          /* disconnect() was called */
 249                rv = -ENODEV;
 250                goto exit;
 251        }
 252
 253        /* if IO is under way, we must not touch things */
 254retry:
 255        spin_lock_irq(&dev->err_lock);
 256        ongoing_io = dev->ongoing_read;
 257        spin_unlock_irq(&dev->err_lock);
 258
 259        if (ongoing_io) {
 260                /* nonblocking IO shall not wait */
 261                if (file->f_flags & O_NONBLOCK) {
 262                        rv = -EAGAIN;
 263                        goto exit;
 264                }
 265                /*
 266                 * IO may take forever
 267                 * hence wait in an interruptible state
 268                 */
 269                rv = wait_for_completion_interruptible(&dev->bulk_in_completion);
 270                if (rv < 0)
 271                        goto exit;
 272                /*
 273                 * by waiting we also semiprocessed the urb
 274                 * we must finish now
 275                 */
 276                dev->bulk_in_copied = 0;
 277                dev->processed_urb = 1;
 278        }
 279
 280        if (!dev->processed_urb) {
 281                /*
 282                 * the URB hasn't been processed
 283                 * do it now
 284                 */
 285                wait_for_completion(&dev->bulk_in_completion);
 286                dev->bulk_in_copied = 0;
 287                dev->processed_urb = 1;
 288        }
 289
 290        /* errors must be reported */
 291        rv = dev->errors;
 292        if (rv < 0) {
 293                /* any error is reported once */
 294                dev->errors = 0;
 295                /* to preserve notifications about reset */
 296                rv = (rv == -EPIPE) ? rv : -EIO;
 297                /* no data to deliver */
 298                dev->bulk_in_filled = 0;
 299                /* report it */
 300                goto exit;
 301        }
 302
 303        /*
 304         * if the buffer is filled we may satisfy the read
 305         * else we need to start IO
 306         */
 307
 308        if (dev->bulk_in_filled) {
 309                /* we had read data */
 310                size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
 311                size_t chunk = min(available, count);
 312
 313                if (!available) {
 314                        /*
 315                         * all data has been used
 316                         * actual IO needs to be done
 317                         */
 318                        rv = skel_do_read_io(dev, count);
 319                        if (rv < 0)
 320                                goto exit;
 321                        else
 322                                goto retry;
 323                }
 324                /*
 325                 * data is available
 326                 * chunk tells us how much shall be copied
 327                 */
 328
 329                if (copy_to_user(buffer,
 330                                 dev->bulk_in_buffer + dev->bulk_in_copied,
 331                                 chunk))
 332                        rv = -EFAULT;
 333                else
 334                        rv = chunk;
 335
 336                dev->bulk_in_copied += chunk;
 337
 338                /*
 339                 * if we are asked for more than we have,
 340                 * we start IO but don't wait
 341                 */
 342                if (available < count)
 343                        skel_do_read_io(dev, count - chunk);
 344        } else {
 345                /* no data in the buffer */
 346                rv = skel_do_read_io(dev, count);
 347                if (rv < 0)
 348                        goto exit;
 349                else if (!(file->f_flags & O_NONBLOCK))
 350                        goto retry;
 351                rv = -EAGAIN;
 352        }
 353exit:
 354        mutex_unlock(&dev->io_mutex);
 355        return rv;
 356}
 357
 358static void skel_write_bulk_callback(struct urb *urb)
 359{
 360        struct usb_skel *dev;
 361
 362        dev = urb->context;
 363
 364        /* sync/async unlink faults aren't errors */
 365        if (urb->status) {
 366                if (!(urb->status == -ENOENT ||
 367                    urb->status == -ECONNRESET ||
 368                    urb->status == -ESHUTDOWN))
 369                        dev_err(&dev->interface->dev,
 370                                "%s - nonzero write bulk status received: %d\n",
 371                                __func__, urb->status);
 372
 373                spin_lock(&dev->err_lock);
 374                dev->errors = urb->status;
 375                spin_unlock(&dev->err_lock);
 376        }
 377
 378        /* free up our allocated buffer */
 379        usb_free_coherent(urb->dev, urb->transfer_buffer_length,
 380                          urb->transfer_buffer, urb->transfer_dma);
 381        up(&dev->limit_sem);
 382}
 383
 384static ssize_t skel_write(struct file *file, const char *user_buffer,
 385                          size_t count, loff_t *ppos)
 386{
 387        struct usb_skel *dev;
 388        int retval = 0;
 389        struct urb *urb = NULL;
 390        char *buf = NULL;
 391        size_t writesize = min(count, (size_t)MAX_TRANSFER);
 392
 393        dev = file->private_data;
 394
 395        /* verify that we actually have some data to write */
 396        if (count == 0)
 397                goto exit;
 398
 399        /*
 400         * limit the number of URBs in flight to stop a user from using up all
 401         * RAM
 402         */
 403        if (!(file->f_flags & O_NONBLOCK)) {
 404                if (down_interruptible(&dev->limit_sem)) {
 405                        retval = -ERESTARTSYS;
 406                        goto exit;
 407                }
 408        } else {
 409                if (down_trylock(&dev->limit_sem)) {
 410                        retval = -EAGAIN;
 411                        goto exit;
 412                }
 413        }
 414
 415        spin_lock_irq(&dev->err_lock);
 416        retval = dev->errors;
 417        if (retval < 0) {
 418                /* any error is reported once */
 419                dev->errors = 0;
 420                /* to preserve notifications about reset */
 421                retval = (retval == -EPIPE) ? retval : -EIO;
 422        }
 423        spin_unlock_irq(&dev->err_lock);
 424        if (retval < 0)
 425                goto error;
 426
 427        /* create a urb, and a buffer for it, and copy the data to the urb */
 428        urb = usb_alloc_urb(0, GFP_KERNEL);
 429        if (!urb) {
 430                retval = -ENOMEM;
 431                goto error;
 432        }
 433
 434        buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
 435                                 &urb->transfer_dma);
 436        if (!buf) {
 437                retval = -ENOMEM;
 438                goto error;
 439        }
 440
 441        if (copy_from_user(buf, user_buffer, writesize)) {
 442                retval = -EFAULT;
 443                goto error;
 444        }
 445
 446        /* this lock makes sure we don't submit URBs to gone devices */
 447        mutex_lock(&dev->io_mutex);
 448        if (!dev->interface) {          /* disconnect() was called */
 449                mutex_unlock(&dev->io_mutex);
 450                retval = -ENODEV;
 451                goto error;
 452        }
 453
 454        /* initialize the urb properly */
 455        usb_fill_bulk_urb(urb, dev->udev,
 456                          usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
 457                          buf, writesize, skel_write_bulk_callback, dev);
 458        urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 459        usb_anchor_urb(urb, &dev->submitted);
 460
 461        /* send the data out the bulk port */
 462        retval = usb_submit_urb(urb, GFP_KERNEL);
 463        mutex_unlock(&dev->io_mutex);
 464        if (retval) {
 465                dev_err(&dev->interface->dev,
 466                        "%s - failed submitting write urb, error %d\n",
 467                        __func__, retval);
 468                goto error_unanchor;
 469        }
 470
 471        /*
 472         * release our reference to this urb, the USB core will eventually free
 473         * it entirely
 474         */
 475        usb_free_urb(urb);
 476
 477
 478        return writesize;
 479
 480error_unanchor:
 481        usb_unanchor_urb(urb);
 482error:
 483        if (urb) {
 484                usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
 485                usb_free_urb(urb);
 486        }
 487        up(&dev->limit_sem);
 488
 489exit:
 490        return retval;
 491}
 492
 493static const struct file_operations skel_fops = {
 494        .owner =        THIS_MODULE,
 495        .read =         skel_read,
 496        .write =        skel_write,
 497        .open =         skel_open,
 498        .release =      skel_release,
 499        .flush =        skel_flush,
 500        .llseek =       noop_llseek,
 501};
 502
 503/*
 504 * usb class driver info in order to get a minor number from the usb core,
 505 * and to have the device registered with the driver core
 506 */
 507static struct usb_class_driver skel_class = {
 508        .name =         "skel%d",
 509        .fops =         &skel_fops,
 510        .minor_base =   USB_SKEL_MINOR_BASE,
 511};
 512
 513static int skel_probe(struct usb_interface *interface,
 514                      const struct usb_device_id *id)
 515{
 516        struct usb_skel *dev;
 517        struct usb_host_interface *iface_desc;
 518        struct usb_endpoint_descriptor *endpoint;
 519        size_t buffer_size;
 520        int i;
 521        int retval = -ENOMEM;
 522
 523        /* allocate memory for our device state and initialize it */
 524        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 525        if (!dev) {
 526                dev_err(&interface->dev, "Out of memory\n");
 527                goto error;
 528        }
 529        kref_init(&dev->kref);
 530        sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
 531        mutex_init(&dev->io_mutex);
 532        spin_lock_init(&dev->err_lock);
 533        init_usb_anchor(&dev->submitted);
 534        init_completion(&dev->bulk_in_completion);
 535
 536        dev->udev = usb_get_dev(interface_to_usbdev(interface));
 537        dev->interface = interface;
 538
 539        /* set up the endpoint information */
 540        /* use only the first bulk-in and bulk-out endpoints */
 541        iface_desc = interface->cur_altsetting;
 542        for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 543                endpoint = &iface_desc->endpoint[i].desc;
 544
 545                if (!dev->bulk_in_endpointAddr &&
 546                    usb_endpoint_is_bulk_in(endpoint)) {
 547                        /* we found a bulk in endpoint */
 548                        buffer_size = usb_endpoint_maxp(endpoint);
 549                        dev->bulk_in_size = buffer_size;
 550                        dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
 551                        dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
 552                        if (!dev->bulk_in_buffer) {
 553                                dev_err(&interface->dev,
 554                                        "Could not allocate bulk_in_buffer\n");
 555                                goto error;
 556                        }
 557                        dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
 558                        if (!dev->bulk_in_urb) {
 559                                dev_err(&interface->dev,
 560                                        "Could not allocate bulk_in_urb\n");
 561                                goto error;
 562                        }
 563                }
 564
 565                if (!dev->bulk_out_endpointAddr &&
 566                    usb_endpoint_is_bulk_out(endpoint)) {
 567                        /* we found a bulk out endpoint */
 568                        dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
 569                }
 570        }
 571        if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
 572                dev_err(&interface->dev,
 573                        "Could not find both bulk-in and bulk-out endpoints\n");
 574                goto error;
 575        }
 576
 577        /* save our data pointer in this interface device */
 578        usb_set_intfdata(interface, dev);
 579
 580        /* we can register the device now, as it is ready */
 581        retval = usb_register_dev(interface, &skel_class);
 582        if (retval) {
 583                /* something prevented us from registering this driver */
 584                dev_err(&interface->dev,
 585                        "Not able to get a minor for this device.\n");
 586                usb_set_intfdata(interface, NULL);
 587                goto error;
 588        }
 589
 590        /* let the user know what node this device is now attached to */
 591        dev_info(&interface->dev,
 592                 "USB Skeleton device now attached to USBSkel-%d",
 593                 interface->minor);
 594        return 0;
 595
 596error:
 597        if (dev)
 598                /* this frees allocated memory */
 599                kref_put(&dev->kref, skel_delete);
 600        return retval;
 601}
 602
 603static void skel_disconnect(struct usb_interface *interface)
 604{
 605        struct usb_skel *dev;
 606        int minor = interface->minor;
 607
 608        dev = usb_get_intfdata(interface);
 609        usb_set_intfdata(interface, NULL);
 610
 611        /* give back our minor */
 612        usb_deregister_dev(interface, &skel_class);
 613
 614        /* prevent more I/O from starting */
 615        mutex_lock(&dev->io_mutex);
 616        dev->interface = NULL;
 617        mutex_unlock(&dev->io_mutex);
 618
 619        usb_kill_anchored_urbs(&dev->submitted);
 620
 621        /* decrement our usage count */
 622        kref_put(&dev->kref, skel_delete);
 623
 624        dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
 625}
 626
 627static void skel_draw_down(struct usb_skel *dev)
 628{
 629        int time;
 630
 631        time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
 632        if (!time)
 633                usb_kill_anchored_urbs(&dev->submitted);
 634        usb_kill_urb(dev->bulk_in_urb);
 635}
 636
 637static int skel_suspend(struct usb_interface *intf, pm_message_t message)
 638{
 639        struct usb_skel *dev = usb_get_intfdata(intf);
 640
 641        if (!dev)
 642                return 0;
 643        skel_draw_down(dev);
 644        return 0;
 645}
 646
 647static int skel_resume(struct usb_interface *intf)
 648{
 649        return 0;
 650}
 651
 652static int skel_pre_reset(struct usb_interface *intf)
 653{
 654        struct usb_skel *dev = usb_get_intfdata(intf);
 655
 656        mutex_lock(&dev->io_mutex);
 657        skel_draw_down(dev);
 658
 659        return 0;
 660}
 661
 662static int skel_post_reset(struct usb_interface *intf)
 663{
 664        struct usb_skel *dev = usb_get_intfdata(intf);
 665
 666        /* we are sure no URBs are active - no locking needed */
 667        dev->errors = -EPIPE;
 668        mutex_unlock(&dev->io_mutex);
 669
 670        return 0;
 671}
 672
 673static struct usb_driver skel_driver = {
 674        .name =         "skeleton",
 675        .probe =        skel_probe,
 676        .disconnect =   skel_disconnect,
 677        .suspend =      skel_suspend,
 678        .resume =       skel_resume,
 679        .pre_reset =    skel_pre_reset,
 680        .post_reset =   skel_post_reset,
 681        .id_table =     skel_table,
 682        .supports_autosuspend = 1,
 683};
 684
 685module_usb_driver(skel_driver);
 686
 687MODULE_LICENSE("GPL");
 688
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