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Docs: usb: update writesize, copy_from_user, usb_fill_bulk_urb, usb_submit_urb

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update code examples writesize, copy_from_user, usb_fill_bulk_urb,
usb_submit_urb in skel_write() according to usb-skeleton.c

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/0c581a83dfc1a8c37e97dfa7279d333f367a9787.1635591623.git.philipp.g.hortmann@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Philipp Hortmann 2021-10-30 13:25:10 +02:00 committed by Greg Kroah-Hartman
parent 925ed163ab
commit 6352f24ba4
1 changed files with 13 additions and 11 deletions
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24
Documentation/driver-api/usb/writing_usb_driver.rst
View File

@ -188,24 +188,26 @@ space, points the urb to the data and submits the urb to the USB
subsystem. This can be seen in the following code::
/* we can only write as much as 1 urb will hold */
bytes_written = (count > skel->bulk_out_size) ? skel->bulk_out_size : count;
size_t writesize = min_t(size_t, count, MAX_TRANSFER);
/* copy the data from user space into our urb */
copy_from_user(skel->write_urb->transfer_buffer, buffer, bytes_written);
copy_from_user(buf, user_buffer, writesize);
/* set up our urb */
usb_fill_bulk_urb(skel->write_urb,
skel->dev,
usb_sndbulkpipe(skel->dev, skel->bulk_out_endpointAddr),
skel->write_urb->transfer_buffer,
bytes_written,
usb_fill_bulk_urb(urb,
dev->udev,
usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
buf,
writesize,
skel_write_bulk_callback,
skel);
dev);
/* send the data out the bulk port */
result = usb_submit_urb(skel->write_urb);
if (result) {
err("Failed submitting write urb, error %d", result);
retval = usb_submit_urb(urb, GFP_KERNEL);
if (retval) {
dev_err(&dev->interface->dev,
"%s - failed submitting write urb, error %d\n",
__func__, retval);
}