drivers/usb/usb-skeleton.c

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