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