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/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 */
  31 static const struct usb_device_id skel_table[] = {
  32         { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
  33         { }                                     /* Terminating entry */
  34 };
  35 MODULE_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 */
  50 struct 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
  72 static struct usb_driver skel_driver;
  73 static void skel_draw_down(struct usb_skel *dev);
  74
  75 static 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
  85 static 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
 123 exit:
 124         return retval;
 125 }
 126
 127 static 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
 146 static 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
 170 static 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
 196 static 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
 230 static 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 */
 254 retry:
 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         }
 353 exit:
 354         mutex_unlock(&dev->io_mutex);
 355         return rv;
 356 }
 357
 358 static 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
 384 static 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
 480 error_unanchor:
 481         usb_unanchor_urb(urb);
 482 error:
 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
 489 exit:
 490         return retval;
 491 }
 492
 493 static 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  */
 507 static struct usb_class_driver skel_class = {
 508         .name =         "skel%d",
 509         .fops =         &skel_fops,
 510         .minor_base =   USB_SKEL_MINOR_BASE,
 511 };
 512
 513 static 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
 596 error:
 597         if (dev)
 598                 /* this frees allocated memory */
 599                 kref_put(&dev->kref, skel_delete);
 600         return retval;
 601 }
 602
 603 static 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
 627 static 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
 637 static 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
 647 static int skel_resume(struct usb_interface *intf)
 648 {
 649         return 0;
 650 }
 651
 652 static 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
 662 static 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
 673 static 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
 685 module_usb_driver(skel_driver);
 686
 687 MODULE_LICENSE("GPL");