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(-) -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
