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