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 /*
  39  * MAX_TRANSFER is chosen so that the VM is not stressed by
  40  * allocations > PAGE_SIZE and the number of packets in a page
  41  * is an integer 512 is the largest possible packet on EHCI
  42  */
  43 #define WRITES_IN_FLIGHT        8
  44 /* arbitrarily chosen */
  45
  46 /* Structure to hold all of our device specific stuff */
  47 struct usb_skel {
  48         struct usb_device       *udev;                  /* the usb device for this device */
  49         struct usb_interface    *interface;             /* the interface for this device */
  50         struct semaphore        limit_sem;              /* limiting the number of writes in progress */
  51         struct usb_anchor       submitted;              /* in case we need to retract our submissions */
  52         struct urb              *bulk_in_urb;           /* the urb to read data with */
  53         unsigned char           *bulk_in_buffer;        /* the buffer to receive data */
  54         size_t                  bulk_in_size;           /* the size of the receive buffer */
  55         size_t                  bulk_in_filled;         /* number of bytes in the buffer */
  56         size_t                  bulk_in_copied;         /* already copied to user space */
  57         __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
  58         __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
  59         int                     errors;                 /* the last request tanked */
  60         bool                    ongoing_read;           /* a read is going on */
  61         spinlock_t              err_lock;               /* lock for errors */
  62         struct kref             kref;
  63         struct mutex            io_mutex;               /* synchronize I/O with disconnect */
  64         wait_queue_head_t       bulk_in_wait;           /* to wait for an ongoing read */
  65 };
  66 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
  67
  68 static struct usb_driver skel_driver;
  69 static void skel_draw_down(struct usb_skel *dev);
  70
  71 static void skel_delete(struct kref *kref)
  72 {
  73         struct usb_skel *dev = to_skel_dev(kref);
  74
  75         usb_free_urb(dev->bulk_in_urb);
  76         usb_put_dev(dev->udev);
  77         kfree(dev->bulk_in_buffer);
  78         kfree(dev);
  79 }
  80
  81 static int skel_open(struct inode *inode, struct file *file)
  82 {
  83         struct usb_skel *dev;
  84         struct usb_interface *interface;
  85         int subminor;
  86         int retval = 0;
  87
  88         subminor = iminor(inode);
  89
  90         interface = usb_find_interface(&skel_driver, subminor);
  91         if (!interface) {
  92                 pr_err("%s - error, can't find device for minor %d\n",
  93                         __func__, subminor);
  94                 retval = -ENODEV;
  95                 goto exit;
  96         }
  97
  98         dev = usb_get_intfdata(interface);
  99         if (!dev) {
 100                 retval = -ENODEV;
 101                 goto exit;
 102         }
 103
 104         retval = usb_autopm_get_interface(interface);
 105         if (retval)
 106                 goto exit;
 107
 108         /* increment our usage count for the device */
 109         kref_get(&dev->kref);
 110
 111         /* save our object in the file's private structure */
 112         file->private_data = dev;
 113
 114 exit:
 115         return retval;
 116 }
 117
 118 static int skel_release(struct inode *inode, struct file *file)
 119 {
 120         struct usb_skel *dev;
 121
 122         dev = file->private_data;
 123         if (dev == NULL)
 124                 return -ENODEV;
 125
 126         /* allow the device to be autosuspended */
 127         mutex_lock(&dev->io_mutex);
 128         if (dev->interface)
 129                 usb_autopm_put_interface(dev->interface);
 130         mutex_unlock(&dev->io_mutex);
 131
 132         /* decrement the count on our device */
 133         kref_put(&dev->kref, skel_delete);
 134         return 0;
 135 }
 136
 137 static int skel_flush(struct file *file, fl_owner_t id)
 138 {
 139         struct usb_skel *dev;
 140         int res;
 141
 142         dev = file->private_data;
 143         if (dev == NULL)
 144                 return -ENODEV;
 145
 146         /* wait for io to stop */
 147         mutex_lock(&dev->io_mutex);
 148         skel_draw_down(dev);
 149
 150         /* read out errors, leave subsequent opens a clean slate */
 151         spin_lock_irq(&dev->err_lock);
 152         res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
 153         dev->errors = 0;
 154         spin_unlock_irq(&dev->err_lock);
 155
 156         mutex_unlock(&dev->io_mutex);
 157
 158         return res;
 159 }
 160
 161 static void skel_read_bulk_callback(struct urb *urb)
 162 {
 163         struct usb_skel *dev;
 164         unsigned long flags;
 165
 166         dev = urb->context;
 167
 168         spin_lock_irqsave(&dev->err_lock, flags);
 169         /* sync/async unlink faults aren't errors */
 170         if (urb->status) {
 171                 if (!(urb->status == -ENOENT ||
 172                     urb->status == -ECONNRESET ||
 173                     urb->status == -ESHUTDOWN))
 174                         dev_err(&dev->interface->dev,
 175                                 "%s - nonzero write bulk status received: %d\n",
 176                                 __func__, urb->status);
 177
 178                 dev->errors = urb->status;
 179         } else {
 180                 dev->bulk_in_filled = urb->actual_length;
 181         }
 182         dev->ongoing_read = 0;
 183         spin_unlock_irqrestore(&dev->err_lock, flags);
 184
 185         wake_up_interruptible(&dev->bulk_in_wait);
 186 }
 187
 188 static int skel_do_read_io(struct usb_skel *dev, size_t count)
 189 {
 190         int rv;
 191
 192         /* prepare a read */
 193         usb_fill_bulk_urb(dev->bulk_in_urb,
 194                         dev->udev,
 195                         usb_rcvbulkpipe(dev->udev,
 196                                 dev->bulk_in_endpointAddr),
 197                         dev->bulk_in_buffer,
 198                         min(dev->bulk_in_size, count),
 199                         skel_read_bulk_callback,
 200                         dev);
 201         /* tell everybody to leave the URB alone */
 202         spin_lock_irq(&dev->err_lock);
 203         dev->ongoing_read = 1;
 204         spin_unlock_irq(&dev->err_lock);
 205
 206         /* submit bulk in urb, which means no data to deliver */
 207         dev->bulk_in_filled = 0;
 208         dev->bulk_in_copied = 0;
 209
 210         /* do it */
 211         rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
 212         if (rv < 0) {
 213                 dev_err(&dev->interface->dev,
 214                         "%s - failed submitting read urb, error %d\n",
 215                         __func__, rv);
 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
 225 static 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 */
 249 retry:
 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_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
 265                 if (rv < 0)
 266                         goto exit;
 267         }
 268
 269         /* errors must be reported */
 270         rv = dev->errors;
 271         if (rv < 0) {
 272                 /* any error is reported once */
 273                 dev->errors = 0;
 274                 /* to preserve notifications about reset */
 275                 rv = (rv == -EPIPE) ? rv : -EIO;
 276                 /* report it */
 277                 goto exit;
 278         }
 279
 280         /*
 281          * if the buffer is filled we may satisfy the read
 282          * else we need to start IO
 283          */
 284
 285         if (dev->bulk_in_filled) {
 286                 /* we had read data */
 287                 size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
 288                 size_t chunk = min(available, count);
 289
 290                 if (!available) {
 291                         /*
 292                          * all data has been used
 293                          * actual IO needs to be done
 294                          */
 295                         rv = skel_do_read_io(dev, count);
 296                         if (rv < 0)
 297                                 goto exit;
 298                         else
 299                                 goto retry;
 300                 }
 301                 /*
 302                  * data is available
 303                  * chunk tells us how much shall be copied
 304                  */
 305
 306                 if (copy_to_user(buffer,
 307                                  dev->bulk_in_buffer + dev->bulk_in_copied,
 308                                  chunk))
 309                         rv = -EFAULT;
 310                 else
 311                         rv = chunk;
 312
 313                 dev->bulk_in_copied += chunk;
 314
 315                 /*
 316                  * if we are asked for more than we have,
 317                  * we start IO but don't wait
 318                  */
 319                 if (available < count)
 320                         skel_do_read_io(dev, count - chunk);
 321         } else {
 322                 /* no data in the buffer */
 323                 rv = skel_do_read_io(dev, count);
 324                 if (rv < 0)
 325                         goto exit;
 326                 else
 327                         goto retry;
 328         }
 329 exit:
 330         mutex_unlock(&dev->io_mutex);
 331         return rv;
 332 }
 333
 334 static void skel_write_bulk_callback(struct urb *urb)
 335 {
 336         struct usb_skel *dev;
 337         unsigned long flags;
 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_irqsave(&dev->err_lock, flags);
 351                 dev->errors = urb->status;
 352                 spin_unlock_irqrestore(&dev->err_lock, flags);
 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 v2");