And here is the actual packet capture that should have been attached in the last mail On 26.04.2018 20:26, Joel Pepper wrote: > I have been doing some work with uvc gadgets, which mirrors the > capabilities of actual webcams attached to a host port. > During testing I ran into -EPIPE errors when trying to retrieve > configurations for more complex devices. > > I tracked the errors down to running over the rather conservative > buffer size of 1024 bytes for config descriptors. This size is > insufficient when dealing with more realistic uvc gadgets, > which need around 50 bytes per framesize per format. > I have attached a packet capture from the setup of a Logitech C270 > (a very common webcam), which sends a config descriptor of 2530 bytes. > > I would have liked to go to 8192 immediately, but I have insufficient > knowledge of the USB spec in general and linux > and hardware implementations in particular, hence this RFC and the more > conservative choice of 4096, which allows for a single versatile > uvc-gadget while leaving headroom for other functions. > > > Joel Pepper (1): > usb: gadget: composite Allow for larger configuration descriptors > > include/linux/usb/composite.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >
Attachment:
logitech-c270-conf-desc-only.pcapng
Description: application/pcapng
