drivers/usb/usb-skeleton.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * USB Skeleton driver - 2.2
   4  *
   5  * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
   6  *
   7  * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
   8  * but has been rewritten to be easier to read and use.
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/errno.h>
  13 #include <linux/slab.h>
  14 #include <linux/module.h>
  15 #include <linux/kref.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/usb.h>
  18 #include <linux/mutex.h>
  19
  20
  21 /* Define these values to match your devices */
  22 #define USB_SKEL_VENDOR_ID      0xfff0
  23 #define USB_SKEL_PRODUCT_ID     0xfff0
  24
  25 /* table of devices that work with this driver */
  26 static const struct usb_device_id skel_table[] = {
  27         { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
  28         { }                                     /* Terminating entry */
  29 };
  30 MODULE_DEVICE_TABLE(usb, skel_table);
  31
  32
  33 /* Get a minor range for your devices from the usb maintainer */
  34 #define USB_SKEL_MINOR_BASE     192
  35
  36 /* our private defines. if this grows any larger, use your own .h file */
  37 #define MAX_TRANSFER            (PAGE_SIZE - 512)
  38 /* MAX_TRANSFER is chosen so that the VM is not stressed by
  39    allocations > PAGE_SIZE and the number of packets in a page
  40    is an integer 512 is the largest possible packet on EHCI */
  41 #define WRITES_IN_FLIGHT        8
  42 /* arbitrarily chosen */
  43
  44 /* Structure to hold all of our device specific stuff */
  45 struct usb_skel {
  46         struct usb_device       *udev;                  /* the usb device for this device */
  47         struct usb_interface    *interface;             /* the interface for this device */
  48         struct semaphore        limit_sem;              /* limiting the number of writes in progress */
  49         struct usb_anchor       submitted;              /* in case we need to retract our submissions */
  50         struct urb              *bulk_in_urb;           /* the urb to read data with */
  51         unsigned char           *bulk_in_buffer;        /* the buffer to receive data */
  52         size_t                  bulk_in_size;           /* the size of the receive buffer */
  53         size_t                  bulk_in_filled;         /* number of bytes in the buffer */
  54         size_t                  bulk_in_copied;         /* already copied to user space */
  55         __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
  56         __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
  57         int                     errors;                 /* the last request tanked */
  58         bool                    ongoing_read;           /* a read is going on */
  59         spinlock_t              err_lock;               /* lock for errors */
  60         struct kref             kref;
  61         struct mutex            io_mutex;               /* synchronize I/O with disconnect */
  62         wait_queue_head_t       bulk_in_wait;           /* to wait for an ongoing read */
  63 };
  64 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
  65
  66 static struct usb_driver skel_driver;
  67 static void skel_draw_down(struct usb_skel *dev);
  68
  69 static void skel_delete(struct kref *kref)
  70 {
  71         struct usb_skel *dev = to_skel_dev(kref);
  72
  73         usb_free_urb(dev->bulk_in_urb);
  74         usb_put_dev(dev->udev);
  75         kfree(dev->bulk_in_buffer);
  76         kfree(dev);
  77 }
  78
  79 static int skel_open(struct inode *inode, struct file *file)
  80 {
  81         struct usb_skel *dev;
  82         struct usb_interface *interface;
  83         int subminor;
  84         int retval = 0;
  85
  86         subminor = iminor(inode);
  87
  88         interface = usb_find_interface(&skel_driver, subminor);
  89         if (!interface) {
  90                 pr_err("%s - error, can't find device for minor %d\n",
  91                         __func__, subminor);
  92                 retval = -ENODEV;
  93                 goto exit;
  94         }
  95
  96         dev = usb_get_intfdata(interface);
  97         if (!dev) {
  98                 retval = -ENODEV;
  99                 goto exit;
 100         }
 101
 102         retval = usb_autopm_get_interface(interface);
 103         if (retval)
 104                 goto exit;
 105
 106         /* increment our usage count for the device */
 107         kref_get(&dev->kref);
 108
 109         /* save our object in the file's private structure */
 110         file->private_data = dev;
 111
 112 exit:
 113         return retval;
 114 }
 115
 116 static int skel_release(struct inode *inode, struct file *file)
 117 {
 118         struct usb_skel *dev;
 119
 120         dev = file->private_data;
 121         if (dev == NULL)
 122                 return -ENODEV;
 123
 124         /* allow the device to be autosuspended */
 125         mutex_lock(&dev->io_mutex);
 126         if (dev->interface)
 127                 usb_autopm_put_interface(dev->interface);
 128         mutex_unlock(&dev->io_mutex);
 129
 130         /* decrement the count on our device */
 131         kref_put(&dev->kref, skel_delete);
 132         return 0;
 133 }
 134
 135 static int skel_flush(struct file *file, fl_owner_t id)
 136 {
 137         struct usb_skel *dev;
 138         int res;
 139
 140         dev = file->private_data;
 141         if (dev == NULL)
 142                 return -ENODEV;
 143
 144         /* wait for io to stop */
 145         mutex_lock(&dev->io_mutex);
 146         skel_draw_down(dev);
 147
 148         /* read out errors, leave subsequent opens a clean slate */
 149         spin_lock_irq(&dev->err_lock);
 150         res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
 151         dev->errors = 0;
 152         spin_unlock_irq(&dev->err_lock);
 153
 154         mutex_unlock(&dev->io_mutex);
 155
 156         return res;
 157 }
 158
 159 static void skel_read_bulk_callback(struct urb *urb)
 160 {
 161         struct usb_skel *dev;
 162         unsigned long flags;
 163
 164         dev = urb->context;
 165
 166         spin_lock_irqsave(&dev->err_lock, flags);
 167         /* sync/async unlink faults aren't errors */
 168         if (urb->status) {
 169                 if (!(urb->status == -ENOENT ||
 170                     urb->status == -ECONNRESET ||
 171                     urb->status == -ESHUTDOWN))
 172                         dev_err(&dev->interface->dev,
 173                                 "%s - nonzero write bulk status received: %d\n",
 174                                 __func__, urb->status);
 175
 176                 dev->errors = urb->status;
 177         } else {
 178                 dev->bulk_in_filled = urb->actual_length;
 179         }
 180         dev->ongoing_read = 0;
 181         spin_unlock_irqrestore(&dev->err_lock, flags);
 182
 183         wake_up_interruptible(&dev->bulk_in_wait);
 184 }
 185
 186 static int skel_do_read_io(struct usb_skel *dev, size_t count)
 187 {
 188         int rv;
 189
 190         /* prepare a read */
 191         usb_fill_bulk_urb(dev->bulk_in_urb,
 192                         dev->udev,
 193                         usb_rcvbulkpipe(dev->udev,
 194                                 dev->bulk_in_endpointAddr),
 195                         dev->bulk_in_buffer,
 196                         min(dev->bulk_in_size, count),
 197                         skel_read_bulk_callback,
 198                         dev);
 199         /* tell everybody to leave the URB alone */
 200         spin_lock_irq(&dev->err_lock);
 201         dev->ongoing_read = 1;
 202         spin_unlock_irq(&dev->err_lock);
 203
 204         /* submit bulk in urb, which means no data to deliver */
 205         dev->bulk_in_filled = 0;
 206         dev->bulk_in_copied = 0;
 207
 208         /* do it */
 209         rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
 210         if (rv < 0) {
 211                 dev_err(&dev->interface->dev,
 212                         "%s - failed submitting read urb, error %d\n",
 213                         __func__, rv);
 214                 rv = (rv == -ENOMEM) ? rv : -EIO;
 215                 spin_lock_irq(&dev->err_lock);
 216                 dev->ongoing_read = 0;
 217                 spin_unlock_irq(&dev->err_lock);
 218         }
 219
 220         return rv;
 221 }
 222
 223 static ssize_t skel_read(struct file *file, char *buffer, size_t count,
 224                          loff_t *ppos)
 225 {
 226         struct usb_skel *dev;
 227         int rv;
 228         bool ongoing_io;
 229
 230         dev = file->private_data;
 231
 232         /* if we cannot read at all, return EOF */
 233         if (!dev->bulk_in_urb || !count)
 234                 return 0;
 235
 236         /* no concurrent readers */
 237         rv = mutex_lock_interruptible(&dev->io_mutex);
 238         if (rv < 0)
 239                 return rv;
 240
 241         if (!dev->interface) {          /* disconnect() was called */
 242                 rv = -ENODEV;
 243                 goto exit;
 244         }
 245
 246         /* if IO is under way, we must not touch things */
 247 retry:
 248         spin_lock_irq(&dev->err_lock);
 249         ongoing_io = dev->ongoing_read;
 250         spin_unlock_irq(&dev->err_lock);
 251
 252         if (ongoing_io) {
 253                 /* nonblocking IO shall not wait */
 254                 if (file->f_flags & O_NONBLOCK) {
 255                         rv = -EAGAIN;
 256                         goto exit;
 257                 }
 258                 /*
 259                  * IO may take forever
 260                  * hence wait in an interruptible state
 261                  */
 262                 rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
 263                 if (rv < 0)
 264                         goto exit;
 265         }
 266
 267         /* errors must be reported */
 268         rv = dev->errors;
 269         if (rv < 0) {
 270                 /* any error is reported once */
 271                 dev->errors = 0;
 272                 /* to preserve notifications about reset */
 273                 rv = (rv == -EPIPE) ? rv : -EIO;
 274                 /* report it */
 275                 goto exit;
 276         }
 277
 278         /*
 279          * if the buffer is filled we may satisfy the read
 280          * else we need to start IO
 281          */
 282
 283         if (dev->bulk_in_filled) {
 284                 /* we had read data */
 285                 size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
 286                 size_t chunk = min(available, count);
 287
 288                 if (!available) {
 289                         /*
 290                          * all data has been used
 291                          * actual IO needs to be done
 292                          */
 293                         rv = skel_do_read_io(dev, count);
 294                         if (rv < 0)
 295                                 goto exit;
 296                         else
 297                                 goto retry;
 298                 }
 299                 /*
 300                  * data is available
 301                  * chunk tells us how much shall be copied
 302                  */
 303
 304                 if (copy_to_user(buffer,
 305                                  dev->bulk_in_buffer + dev->bulk_in_copied,
 306                                  chunk))
 307                         rv = -EFAULT;
 308                 else
 309                         rv = chunk;
 310
 311                 dev->bulk_in_copied += chunk;
 312
 313                 /*
 314                  * if we are asked for more than we have,
 315                  * we start IO but don't wait
 316                  */
 317                 if (available < count)
 318                         skel_do_read_io(dev, count - chunk);
 319         } else {
 320                 /* no data in the buffer */
 321                 rv = skel_do_read_io(dev, count);
 322                 if (rv < 0)
 323                         goto exit;
 324                 else
 325                         goto retry;
 326         }
 327 exit:
 328         mutex_unlock(&dev->io_mutex);
 329         return rv;
 330 }
 331
 332 static void skel_write_bulk_callback(struct urb *urb)
 333 {
 334         struct usb_skel *dev;
 335         unsigned long flags;
 336
 337         dev = urb->context;
 338
 339         /* sync/async unlink faults aren't errors */
 340         if (urb->status) {
 341                 if (!(urb->status == -ENOENT ||
 342                     urb->status == -ECONNRESET ||
 343                     urb->status == -ESHUTDOWN))
 344                         dev_err(&dev->interface->dev,
 345                                 "%s - nonzero write bulk status received: %d\n",
 346                                 __func__, urb->status);
 347
 348                 spin_lock_irqsave(&dev->err_lock, flags);
 349                 dev->errors = urb->status;
 350                 spin_unlock_irqrestore(&dev->err_lock, flags);
 351         }
 352
 353         /* free up our allocated buffer */
 354         usb_free_coherent(urb->dev, urb->transfer_buffer_length,
 355                           urb->transfer_buffer, urb->transfer_dma);
 356         up(&dev->limit_sem);
 357 }
 358
 359 static ssize_t skel_write(struct file *file, const char *user_buffer,
 360                           size_t count, loff_t *ppos)
 361 {
 362         struct usb_skel *dev;
 363         int retval = 0;
 364         struct urb *urb = NULL;
 365         char *buf = NULL;
 366         size_t writesize = min(count, (size_t)MAX_TRANSFER);
 367
 368         dev = file->private_data;
 369
 370         /* verify that we actually have some data to write */
 371         if (count == 0)
 372                 goto exit;
 373
 374         /*
 375          * limit the number of URBs in flight to stop a user from using up all
 376          * RAM
 377          */
 378         if (!(file->f_flags & O_NONBLOCK)) {
 379                 if (down_interruptible(&dev->limit_sem)) {
 380                         retval = -ERESTARTSYS;
 381                         goto exit;
 382                 }
 383         } else {
 384                 if (down_trylock(&dev->limit_sem)) {
 385                         retval = -EAGAIN;
 386                         goto exit;
 387                 }
 388         }
 389
 390         spin_lock_irq(&dev->err_lock);
 391         retval = dev->errors;
 392         if (retval < 0) {
 393                 /* any error is reported once */
 394                 dev->errors = 0;
 395                 /* to preserve notifications about reset */
 396                 retval = (retval == -EPIPE) ? retval : -EIO;
 397         }
 398         spin_unlock_irq(&dev->err_lock);
 399         if (retval < 0)
 400                 goto error;
 401
 402         /* create a urb, and a buffer for it, and copy the data to the urb */
 403         urb = usb_alloc_urb(0, GFP_KERNEL);
 404         if (!urb) {
 405                 retval = -ENOMEM;
 406                 goto error;
 407         }
 408
 409         buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
 410                                  &urb->transfer_dma);
 411         if (!buf) {
 412                 retval = -ENOMEM;
 413                 goto error;
 414         }
 415
 416         if (copy_from_user(buf, user_buffer, writesize)) {
 417                 retval = -EFAULT;
 418                 goto error;
 419         }
 420
 421         /* this lock makes sure we don't submit URBs to gone devices */
 422         mutex_lock(&dev->io_mutex);
 423         if (!dev->interface) {          /* disconnect() was called */
 424                 mutex_unlock(&dev->io_mutex);
 425                 retval = -ENODEV;
 426                 goto error;
 427         }
 428
 429         /* initialize the urb properly */
 430         usb_fill_bulk_urb(urb, dev->udev,
 431                           usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
 432                           buf, writesize, skel_write_bulk_callback, dev);
 433         urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 434         usb_anchor_urb(urb, &dev->submitted);
 435
 436         /* send the data out the bulk port */
 437         retval = usb_submit_urb(urb, GFP_KERNEL);
 438         mutex_unlock(&dev->io_mutex);
 439         if (retval) {
 440                 dev_err(&dev->interface->dev,
 441                         "%s - failed submitting write urb, error %d\n",
 442                         __func__, retval);
 443                 goto error_unanchor;
 444         }
 445
 446         /*
 447          * release our reference to this urb, the USB core will eventually free
 448          * it entirely
 449          */
 450         usb_free_urb(urb);
 451
 452
 453         return writesize;
 454
 455 error_unanchor:
 456         usb_unanchor_urb(urb);
 457 error:
 458         if (urb) {
 459                 usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
 460                 usb_free_urb(urb);
 461         }
 462         up(&dev->limit_sem);
 463
 464 exit:
 465         return retval;
 466 }
 467
 468 static const struct file_operations skel_fops = {
 469         .owner =        THIS_MODULE,
 470         .read =         skel_read,
 471         .write =        skel_write,
 472         .open =         skel_open,
 473         .release =      skel_release,
 474         .flush =        skel_flush,
 475         .llseek =       noop_llseek,
 476 };
 477
 478 /*
 479  * usb class driver info in order to get a minor number from the usb core,
 480  * and to have the device registered with the driver core
 481  */
 482 static struct usb_class_driver skel_class = {
 483         .name =         "skel%d",
 484         .fops =         &skel_fops,
 485         .minor_base =   USB_SKEL_MINOR_BASE,
 486 };
 487
 488 static int skel_probe(struct usb_interface *interface,
 489                       const struct usb_device_id *id)
 490 {
 491         struct usb_skel *dev;
 492         struct usb_endpoint_descriptor *bulk_in, *bulk_out;
 493         int retval;
 494
 495         /* allocate memory for our device state and initialize it */
 496         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 497         if (!dev)
 498                 return -ENOMEM;
 499
 500         kref_init(&dev->kref);
 501         sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
 502         mutex_init(&dev->io_mutex);
 503         spin_lock_init(&dev->err_lock);
 504         init_usb_anchor(&dev->submitted);
 505         init_waitqueue_head(&dev->bulk_in_wait);
 506
 507         dev->udev = usb_get_dev(interface_to_usbdev(interface));
 508         dev->interface = interface;
 509
 510         /* set up the endpoint information */
 511         /* use only the first bulk-in and bulk-out endpoints */
 512         retval = usb_find_common_endpoints(interface->cur_altsetting,
 513                         &bulk_in, &bulk_out, NULL, NULL);
 514         if (retval) {
 515                 dev_err(&interface->dev,
 516                         "Could not find both bulk-in and bulk-out endpoints\n");
 517                 goto error;
 518         }
 519
 520         dev->bulk_in_size = usb_endpoint_maxp(bulk_in);
 521         dev->bulk_in_endpointAddr = bulk_in->bEndpointAddress;
 522         dev->bulk_in_buffer = kmalloc(dev->bulk_in_size, GFP_KERNEL);
 523         if (!dev->bulk_in_buffer) {
 524                 retval = -ENOMEM;
 525                 goto error;
 526         }
 527         dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
 528         if (!dev->bulk_in_urb) {
 529                 retval = -ENOMEM;
 530                 goto error;
 531         }
 532
 533         dev->bulk_out_endpointAddr = bulk_out->bEndpointAddress;
 534
 535         /* save our data pointer in this interface device */
 536         usb_set_intfdata(interface, dev);
 537
 538         /* we can register the device now, as it is ready */
 539         retval = usb_register_dev(interface, &skel_class);
 540         if (retval) {
 541                 /* something prevented us from registering this driver */
 542                 dev_err(&interface->dev,
 543                         "Not able to get a minor for this device.\n");
 544                 usb_set_intfdata(interface, NULL);
 545                 goto error;
 546         }
 547
 548         /* let the user know what node this device is now attached to */
 549         dev_info(&interface->dev,
 550                  "USB Skeleton device now attached to USBSkel-%d",
 551                  interface->minor);
 552         return 0;
 553
 554 error:
 555         /* this frees allocated memory */
 556         kref_put(&dev->kref, skel_delete);
 557
 558         return retval;
 559 }
 560
 561 static void skel_disconnect(struct usb_interface *interface)
 562 {
 563         struct usb_skel *dev;
 564         int minor = interface->minor;
 565
 566         dev = usb_get_intfdata(interface);
 567         usb_set_intfdata(interface, NULL);
 568
 569         /* give back our minor */
 570         usb_deregister_dev(interface, &skel_class);
 571
 572         /* prevent more I/O from starting */
 573         mutex_lock(&dev->io_mutex);
 574         dev->interface = NULL;
 575         mutex_unlock(&dev->io_mutex);
 576
 577         usb_kill_anchored_urbs(&dev->submitted);
 578
 579         /* decrement our usage count */
 580         kref_put(&dev->kref, skel_delete);
 581
 582         dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
 583 }
 584
 585 static void skel_draw_down(struct usb_skel *dev)
 586 {
 587         int time;
 588
 589         time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
 590         if (!time)
 591                 usb_kill_anchored_urbs(&dev->submitted);
 592         usb_kill_urb(dev->bulk_in_urb);
 593 }
 594
 595 static int skel_suspend(struct usb_interface *intf, pm_message_t message)
 596 {
 597         struct usb_skel *dev = usb_get_intfdata(intf);
 598
 599         if (!dev)
 600                 return 0;
 601         skel_draw_down(dev);
 602         return 0;
 603 }
 604
 605 static int skel_resume(struct usb_interface *intf)
 606 {
 607         return 0;
 608 }
 609
 610 static int skel_pre_reset(struct usb_interface *intf)
 611 {
 612         struct usb_skel *dev = usb_get_intfdata(intf);
 613
 614         mutex_lock(&dev->io_mutex);
 615         skel_draw_down(dev);
 616
 617         return 0;
 618 }
 619
 620 static int skel_post_reset(struct usb_interface *intf)
 621 {
 622         struct usb_skel *dev = usb_get_intfdata(intf);
 623
 624         /* we are sure no URBs are active - no locking needed */
 625         dev->errors = -EPIPE;
 626         mutex_unlock(&dev->io_mutex);
 627
 628         return 0;
 629 }
 630
 631 static struct usb_driver skel_driver = {
 632         .name =         "skeleton",
 633         .probe =        skel_probe,
 634         .disconnect =   skel_disconnect,
 635         .suspend =      skel_suspend,
 636         .resume =       skel_resume,
 637         .pre_reset =    skel_pre_reset,
 638         .post_reset =   skel_post_reset,
 639         .id_table =     skel_table,
 640         .supports_autosuspend = 1,
 641 };
 642
 643 module_usb_driver(skel_driver);
 644
 645 MODULE_LICENSE("GPL v2");