On Fri, May 31, 2019 at 01:04:12PM -0700, Douglas Anderson wrote:
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 Signed-off-by: Douglas Anderson dianders@chromium.org
I'm not really familiar with the dwc2 driver, but this looks reasonable to me. FWIW:
Reviewed-by: Matthias Kaehlcke mka@chromium.org