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 unsigned long disconnected:1;
65 wait_queue_head_t bulk_in_wait; /* to wait for an ongoing read */
67 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
69 static struct usb_driver skel_driver;
70 static void skel_draw_down(struct usb_skel *dev);
72 static void skel_delete(struct kref *kref)
74 struct usb_skel *dev = to_skel_dev(kref);
76 usb_free_urb(dev->bulk_in_urb);
77 usb_put_intf(dev->interface);
78 usb_put_dev(dev->udev);
79 kfree(dev->bulk_in_buffer);
83 static int skel_open(struct inode *inode, struct file *file)
86 struct usb_interface *interface;
90 subminor = iminor(inode);
92 interface = usb_find_interface(&skel_driver, subminor);
94 pr_err("%s - error, can't find device for minor %d\n",
100 dev = usb_get_intfdata(interface);
106 retval = usb_autopm_get_interface(interface);
110 /* increment our usage count for the device */
111 kref_get(&dev->kref);
113 /* save our object in the file's private structure */
114 file->private_data = dev;
120 static int skel_release(struct inode *inode, struct file *file)
122 struct usb_skel *dev;
124 dev = file->private_data;
128 /* allow the device to be autosuspended */
129 usb_autopm_put_interface(dev->interface);
131 /* decrement the count on our device */
132 kref_put(&dev->kref, skel_delete);
136 static int skel_flush(struct file *file, fl_owner_t id)
138 struct usb_skel *dev;
141 dev = file->private_data;
145 /* wait for io to stop */
146 mutex_lock(&dev->io_mutex);
149 /* read out errors, leave subsequent opens a clean slate */
150 spin_lock_irq(&dev->err_lock);
151 res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
153 spin_unlock_irq(&dev->err_lock);
155 mutex_unlock(&dev->io_mutex);
160 static void skel_read_bulk_callback(struct urb *urb)
162 struct usb_skel *dev;
167 spin_lock_irqsave(&dev->err_lock, flags);
168 /* sync/async unlink faults aren't errors */
170 if (!(urb->status == -ENOENT ||
171 urb->status == -ECONNRESET ||
172 urb->status == -ESHUTDOWN))
173 dev_err(&dev->interface->dev,
174 "%s - nonzero write bulk status received: %d\n",
175 __func__, urb->status);
177 dev->errors = urb->status;
179 dev->bulk_in_filled = urb->actual_length;
181 dev->ongoing_read = 0;
182 spin_unlock_irqrestore(&dev->err_lock, flags);
184 wake_up_interruptible(&dev->bulk_in_wait);
187 static int skel_do_read_io(struct usb_skel *dev, size_t count)
192 usb_fill_bulk_urb(dev->bulk_in_urb,
194 usb_rcvbulkpipe(dev->udev,
195 dev->bulk_in_endpointAddr),
197 min(dev->bulk_in_size, count),
198 skel_read_bulk_callback,
200 /* tell everybody to leave the URB alone */
201 spin_lock_irq(&dev->err_lock);
202 dev->ongoing_read = 1;
203 spin_unlock_irq(&dev->err_lock);
205 /* submit bulk in urb, which means no data to deliver */
206 dev->bulk_in_filled = 0;
207 dev->bulk_in_copied = 0;
210 rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
212 dev_err(&dev->interface->dev,
213 "%s - failed submitting read urb, error %d\n",
215 rv = (rv == -ENOMEM) ? rv : -EIO;
216 spin_lock_irq(&dev->err_lock);
217 dev->ongoing_read = 0;
218 spin_unlock_irq(&dev->err_lock);
224 static ssize_t skel_read(struct file *file, char *buffer, size_t count,
227 struct usb_skel *dev;
231 dev = file->private_data;
236 /* no concurrent readers */
237 rv = mutex_lock_interruptible(&dev->io_mutex);
241 if (dev->disconnected) { /* disconnect() was called */
246 /* if IO is under way, we must not touch things */
248 spin_lock_irq(&dev->err_lock);
249 ongoing_io = dev->ongoing_read;
250 spin_unlock_irq(&dev->err_lock);
253 /* nonblocking IO shall not wait */
254 if (file->f_flags & O_NONBLOCK) {
259 * IO may take forever
260 * hence wait in an interruptible state
262 rv = wait_event_interruptible(dev->bulk_in_wait, (!dev->ongoing_read));
267 /* errors must be reported */
270 /* any error is reported once */
272 /* to preserve notifications about reset */
273 rv = (rv == -EPIPE) ? rv : -EIO;
279 * if the buffer is filled we may satisfy the read
280 * else we need to start IO
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);
290 * all data has been used
291 * actual IO needs to be done
293 rv = skel_do_read_io(dev, count);
301 * chunk tells us how much shall be copied
304 if (copy_to_user(buffer,
305 dev->bulk_in_buffer + dev->bulk_in_copied,
311 dev->bulk_in_copied += chunk;
314 * if we are asked for more than we have,
315 * we start IO but don't wait
317 if (available < count)
318 skel_do_read_io(dev, count - chunk);
320 /* no data in the buffer */
321 rv = skel_do_read_io(dev, count);
328 mutex_unlock(&dev->io_mutex);
332 static void skel_write_bulk_callback(struct urb *urb)
334 struct usb_skel *dev;
339 /* sync/async unlink faults aren't errors */
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);
348 spin_lock_irqsave(&dev->err_lock, flags);
349 dev->errors = urb->status;
350 spin_unlock_irqrestore(&dev->err_lock, flags);
353 /* free up our allocated buffer */
354 usb_free_coherent(urb->dev, urb->transfer_buffer_length,
355 urb->transfer_buffer, urb->transfer_dma);
359 static ssize_t skel_write(struct file *file, const char *user_buffer,
360 size_t count, loff_t *ppos)
362 struct usb_skel *dev;
364 struct urb *urb = NULL;
366 size_t writesize = min(count, (size_t)MAX_TRANSFER);
368 dev = file->private_data;
370 /* verify that we actually have some data to write */
375 * limit the number of URBs in flight to stop a user from using up all
378 if (!(file->f_flags & O_NONBLOCK)) {
379 if (down_interruptible(&dev->limit_sem)) {
380 retval = -ERESTARTSYS;
384 if (down_trylock(&dev->limit_sem)) {
390 spin_lock_irq(&dev->err_lock);
391 retval = dev->errors;
393 /* any error is reported once */
395 /* to preserve notifications about reset */
396 retval = (retval == -EPIPE) ? retval : -EIO;
398 spin_unlock_irq(&dev->err_lock);
402 /* create a urb, and a buffer for it, and copy the data to the urb */
403 urb = usb_alloc_urb(0, GFP_KERNEL);
409 buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
416 if (copy_from_user(buf, user_buffer, writesize)) {
421 /* this lock makes sure we don't submit URBs to gone devices */
422 mutex_lock(&dev->io_mutex);
423 if (dev->disconnected) { /* disconnect() was called */
424 mutex_unlock(&dev->io_mutex);
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);
436 /* send the data out the bulk port */
437 retval = usb_submit_urb(urb, GFP_KERNEL);
438 mutex_unlock(&dev->io_mutex);
440 dev_err(&dev->interface->dev,
441 "%s - failed submitting write urb, error %d\n",
447 * release our reference to this urb, the USB core will eventually free
456 usb_unanchor_urb(urb);
459 usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
468 static const struct file_operations skel_fops = {
469 .owner = THIS_MODULE,
473 .release = skel_release,
475 .llseek = noop_llseek,
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
482 static struct usb_class_driver skel_class = {
485 .minor_base = USB_SKEL_MINOR_BASE,
488 static int skel_probe(struct usb_interface *interface,
489 const struct usb_device_id *id)
491 struct usb_skel *dev;
492 struct usb_endpoint_descriptor *bulk_in, *bulk_out;
495 /* allocate memory for our device state and initialize it */
496 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
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);
507 dev->udev = usb_get_dev(interface_to_usbdev(interface));
508 dev->interface = usb_get_intf(interface);
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);
515 dev_err(&interface->dev,
516 "Could not find both bulk-in and bulk-out endpoints\n");
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) {
527 dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
528 if (!dev->bulk_in_urb) {
533 dev->bulk_out_endpointAddr = bulk_out->bEndpointAddress;
535 /* save our data pointer in this interface device */
536 usb_set_intfdata(interface, dev);
538 /* we can register the device now, as it is ready */
539 retval = usb_register_dev(interface, &skel_class);
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);
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",
555 /* this frees allocated memory */
556 kref_put(&dev->kref, skel_delete);
561 static void skel_disconnect(struct usb_interface *interface)
563 struct usb_skel *dev;
564 int minor = interface->minor;
566 dev = usb_get_intfdata(interface);
567 usb_set_intfdata(interface, NULL);
569 /* give back our minor */
570 usb_deregister_dev(interface, &skel_class);
572 /* prevent more I/O from starting */
573 mutex_lock(&dev->io_mutex);
574 dev->disconnected = 1;
575 mutex_unlock(&dev->io_mutex);
577 usb_kill_urb(dev->bulk_in_urb);
578 usb_kill_anchored_urbs(&dev->submitted);
580 /* decrement our usage count */
581 kref_put(&dev->kref, skel_delete);
583 dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
586 static void skel_draw_down(struct usb_skel *dev)
590 time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
592 usb_kill_anchored_urbs(&dev->submitted);
593 usb_kill_urb(dev->bulk_in_urb);
596 static int skel_suspend(struct usb_interface *intf, pm_message_t message)
598 struct usb_skel *dev = usb_get_intfdata(intf);
606 static int skel_resume(struct usb_interface *intf)
611 static int skel_pre_reset(struct usb_interface *intf)
613 struct usb_skel *dev = usb_get_intfdata(intf);
615 mutex_lock(&dev->io_mutex);
621 static int skel_post_reset(struct usb_interface *intf)
623 struct usb_skel *dev = usb_get_intfdata(intf);
625 /* we are sure no URBs are active - no locking needed */
626 dev->errors = -EPIPE;
627 mutex_unlock(&dev->io_mutex);
632 static struct usb_driver skel_driver = {
635 .disconnect = skel_disconnect,
636 .suspend = skel_suspend,
637 .resume = skel_resume,
638 .pre_reset = skel_pre_reset,
639 .post_reset = skel_post_reset,
640 .id_table = skel_table,
641 .supports_autosuspend = 1,
644 module_usb_driver(skel_driver);
646 MODULE_LICENSE("GPL v2");