babd183915
In commit abb621844f6a ("usb: ch9: make usb_endpoint_maxp() return
only packet size") the API to usb_endpoint_maxp() changed. It used to
just return wMaxPacketSize but after that commit it returned
wMaxPacketSize with the high bits (the multiplier) masked off. If you
wanted to get the multiplier it was now up to your code to call the
new usb_endpoint_maxp_mult() which was introduced in
commit 541b6fe63023 ("usb: add helper to extract bits 12:11 of
wMaxPacketSize").
Prior to the API change most host drivers were updated, but no update
was made to dwc2. Presumably it was assumed that dwc2 was too
simplistic to use the multiplier and thus just didn't support a
certain class of USB devices. However, it turns out that dwc2 did use
the multiplier and many devices using it were working quite nicely.
That means that many USB devices have been broken since the API
change. One such device is a Logitech HD Pro Webcam C920.
Specifically, though dwc2 didn't directly call usb_endpoint_maxp(), it
did call usb_maxpacket() which in turn called usb_endpoint_maxp().
Let's update dwc2 to work properly with the new API.
Fixes: abb621844f6a ("usb: ch9: make usb_endpoint_maxp() return only packet size")
Cc: stable@vger.kernel.org
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.