1 // SPDX-License-Identifier: GPL-2.0
3 * USB Skeleton driver - 2.2
5 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
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.
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>
21 /* Define these values to match your devices */
22 #define USB_SKEL_VENDOR_ID 0xfff0
23 #define USB_SKEL_PRODUCT_ID 0xfff0
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 */
30 MODULE_DEVICE_TABLE(usb, skel_table);
33 /* Get a minor range for your devices from the usb maintainer */
34 #define USB_SKEL_MINOR_BASE 192
36 /* our private defines. if this grows any larger, use your own .h file */
37 #define MAX_TRANSFER (PAGE_SIZE - 512)
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
43 #define WRITES_IN_FLIGHT 8
44 /* arbitrarily chosen */
46 /* Structure to hold all of our device specific stuff */
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 */
63 struct mutex io_mutex; /* synchronize I/O with disconnect */
64 wait_queue_head_t bulk_in_wait; /* to wait for an ongoing read */
66 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
68 static struct usb_driver skel_driver;
69 static void skel_draw_down(struct usb_skel *dev);
71 static void skel_delete(struct kref *kref)
73 struct usb_skel *dev = to_skel_dev(kref);
75 usb_free_urb(dev->bulk_in_urb);
76 usb_put_dev(dev->udev);
77 kfree(dev->bulk_in_buffer);
81 static int skel_open(struct inode *inode, struct file *file)
84 struct usb_interface *interface;
88 subminor = iminor(inode);
90 interface = usb_find_interface(&skel_driver, subminor);
92 pr_err("%s - error, can't find device for minor %d\n",
98 dev = usb_get_intfdata(interface);
104 retval = usb_autopm_get_interface(interface);
108 /* increment our usage count for the device */
109 kref_get(&dev->kref);
111 /* save our object in the file's private structure */
112 file->private_data = dev;
118 static int skel_release(struct inode *inode, struct file *file)
120 struct usb_skel *dev;
122 dev = file->private_data;
126 /* allow the device to be autosuspended */
127 mutex_lock(&dev->io_mutex);
129 usb_autopm_put_interface(dev->interface);
130 mutex_unlock(&dev->io_mutex);
132 /* decrement the count on our device */
133 kref_put(&dev->kref, skel_delete);
137 static int skel_flush(struct file *file, fl_owner_t id)
139 struct usb_skel *dev;
142 dev = file->private_data;
146 /* wait for io to stop */
147 mutex_lock(&dev->io_mutex);
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;
154 spin_unlock_irq(&dev->err_lock);
156 mutex_unlock(&dev->io_mutex);
161 static void skel_read_bulk_callback(struct urb *urb)
163 struct usb_skel *dev;
168 spin_lock_irqsave(&dev->err_lock, flags);
169 /* sync/async unlink faults aren't errors */
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);
178 dev->errors = urb->status;
180 dev->bulk_in_filled = urb->actual_length;
182 dev->ongoing_read = 0;
183 spin_unlock_irqrestore(&dev->err_lock, flags);
185 wake_up_interruptible(&dev->bulk_in_wait);
188 static int skel_do_read_io(struct usb_skel *dev, size_t count)
193 usb_fill_bulk_urb(dev->bulk_in_urb,
195 usb_rcvbulkpipe(dev->udev,
196 dev->bulk_in_endpointAddr),
198 min(dev->bulk_in_size, count),
199 skel_read_bulk_callback,
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);
206 /* submit bulk in urb, which means no data to deliver */
207 dev->bulk_in_filled = 0;
208 dev->bulk_in_copied = 0;
211 rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
213 dev_err(&dev->interface->dev,
214 "%s - failed submitting read urb, error %d\n",
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);
225 static ssize_t skel_read(struct file *file, char *buffer, size_t count,
228 struct usb_skel *dev;
232 dev = file->private_data;
234 /* if we cannot read at all, return EOF */
235 if (!dev->bulk_in_urb || !count)
238 /* no concurrent readers */
239 rv = mutex_lock_interruptible(&dev->io_mutex);
243 if (!dev->interface) { /* disconnect() was called */
248 /* if IO is under way, we must not touch things */
250 spin_lock_irq(&dev->err_lock);
251 ongoing_io = dev->ongoing_read;
252 spin_unlock_irq(&dev->err_lock);
255 /* nonblocking IO shall not wait */
256 if (file->f_flags & O_NONBLOCK) {
261 * IO may take forever
262 * hence wait in an interruptible state
264 rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
269 /* errors must be reported */
272 /* any error is reported once */
274 /* to preserve notifications about reset */
275 rv = (rv == -EPIPE) ? rv : -EIO;
281 * if the buffer is filled we may satisfy the read
282 * else we need to start IO
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);
292 * all data has been used
293 * actual IO needs to be done
295 rv = skel_do_read_io(dev, count);
303 * chunk tells us how much shall be copied
306 if (copy_to_user(buffer,
307 dev->bulk_in_buffer + dev->bulk_in_copied,
313 dev->bulk_in_copied += chunk;
316 * if we are asked for more than we have,
317 * we start IO but don't wait
319 if (available < count)
320 skel_do_read_io(dev, count - chunk);
322 /* no data in the buffer */
323 rv = skel_do_read_io(dev, count);
330 mutex_unlock(&dev->io_mutex);
334 static void skel_write_bulk_callback(struct urb *urb)
336 struct usb_skel *dev;
341 /* sync/async unlink faults aren't errors */
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);
350 spin_lock_irqsave(&dev->err_lock, flags);
351 dev->errors = urb->status;
352 spin_unlock_irqrestore(&dev->err_lock, flags);
355 /* free up our allocated buffer */
356 usb_free_coherent(urb->dev, urb->transfer_buffer_length,
357 urb->transfer_buffer, urb->transfer_dma);
361 static ssize_t skel_write(struct file *file, const char *user_buffer,
362 size_t count, loff_t *ppos)
364 struct usb_skel *dev;
366 struct urb *urb = NULL;
368 size_t writesize = min(count, (size_t)MAX_TRANSFER);
370 dev = file->private_data;
372 /* verify that we actually have some data to write */
377 * limit the number of URBs in flight to stop a user from using up all
380 if (!(file->f_flags & O_NONBLOCK)) {
381 if (down_interruptible(&dev->limit_sem)) {
382 retval = -ERESTARTSYS;
386 if (down_trylock(&dev->limit_sem)) {
392 spin_lock_irq(&dev->err_lock);
393 retval = dev->errors;
395 /* any error is reported once */
397 /* to preserve notifications about reset */
398 retval = (retval == -EPIPE) ? retval : -EIO;
400 spin_unlock_irq(&dev->err_lock);
404 /* create a urb, and a buffer for it, and copy the data to the urb */
405 urb = usb_alloc_urb(0, GFP_KERNEL);
411 buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
418 if (copy_from_user(buf, user_buffer, writesize)) {
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);
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);
438 /* send the data out the bulk port */
439 retval = usb_submit_urb(urb, GFP_KERNEL);
440 mutex_unlock(&dev->io_mutex);
442 dev_err(&dev->interface->dev,
443 "%s - failed submitting write urb, error %d\n",
449 * release our reference to this urb, the USB core will eventually free
458 usb_unanchor_urb(urb);
461 usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
470 static const struct file_operations skel_fops = {
471 .owner = THIS_MODULE,
475 .release = skel_release,
477 .llseek = noop_llseek,
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
484 static struct usb_class_driver skel_class = {
487 .minor_base = USB_SKEL_MINOR_BASE,
490 static int skel_probe(struct usb_interface *interface,
491 const struct usb_device_id *id)
493 struct usb_skel *dev;
494 struct usb_endpoint_descriptor *bulk_in, *bulk_out;
497 /* allocate memory for our device state and initialize it */
498 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
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);
509 dev->udev = usb_get_dev(interface_to_usbdev(interface));
510 dev->interface = interface;
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);
517 dev_err(&interface->dev,
518 "Could not find both bulk-in and bulk-out endpoints\n");
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) {
529 dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
530 if (!dev->bulk_in_urb) {
535 dev->bulk_out_endpointAddr = bulk_out->bEndpointAddress;
537 /* save our data pointer in this interface device */
538 usb_set_intfdata(interface, dev);
540 /* we can register the device now, as it is ready */
541 retval = usb_register_dev(interface, &skel_class);
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);
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",
557 /* this frees allocated memory */
558 kref_put(&dev->kref, skel_delete);
563 static void skel_disconnect(struct usb_interface *interface)
565 struct usb_skel *dev;
566 int minor = interface->minor;
568 dev = usb_get_intfdata(interface);
569 usb_set_intfdata(interface, NULL);
571 /* give back our minor */
572 usb_deregister_dev(interface, &skel_class);
574 /* prevent more I/O from starting */
575 mutex_lock(&dev->io_mutex);
576 dev->interface = NULL;
577 mutex_unlock(&dev->io_mutex);
579 usb_kill_anchored_urbs(&dev->submitted);
581 /* decrement our usage count */
582 kref_put(&dev->kref, skel_delete);
584 dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
587 static void skel_draw_down(struct usb_skel *dev)
591 time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
593 usb_kill_anchored_urbs(&dev->submitted);
594 usb_kill_urb(dev->bulk_in_urb);
597 static int skel_suspend(struct usb_interface *intf, pm_message_t message)
599 struct usb_skel *dev = usb_get_intfdata(intf);
607 static int skel_resume(struct usb_interface *intf)
612 static int skel_pre_reset(struct usb_interface *intf)
614 struct usb_skel *dev = usb_get_intfdata(intf);
616 mutex_lock(&dev->io_mutex);
622 static int skel_post_reset(struct usb_interface *intf)
624 struct usb_skel *dev = usb_get_intfdata(intf);
626 /* we are sure no URBs are active - no locking needed */
627 dev->errors = -EPIPE;
628 mutex_unlock(&dev->io_mutex);
633 static struct usb_driver skel_driver = {
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,
645 module_usb_driver(skel_driver);
647 MODULE_LICENSE("GPL v2");