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"); 646