On Wednesday 22 April 2009 00:23:18 Alan Stern wrote: > > So, my next question is if there's any way for me to reverse the firmware > > to fix the real problem and if not is there a way to fix the bInterval > > value for this device? Possibly something like the various hid drivers > > such as hid-lg.c for hid quirks? > > I don't know anything about the device's firmware; you'll probably have > to complain to the manufacturer and ask them to fix it. Both the 17x > behavior and the incorrect bInterval value. Sorry, I didn't explain myself very well, I was wondering if there is any information/are any tutorials on how to work out what the firmware is doing. Perhaps disassembling or even decompiling the firmware code. I searched on Google but I couldn't find anything useful. > Yes, you certainly can add a special HID driver for this device. But > fixing the firmware would be preferable. If this can't be fixed in firmware, I've found there is a quirk in include/linux/hid.h defined as HID_QUIRK_FULLSPEED_INTERVAL. In drivers/hid/usbhid/hid-quirks.c there is a blacklist which includes the Afatech AF9016. Since this is the Afatech AF9015 it would appear that this is the next best way to handle the problem (I tested it and it seemed to work here). > I meant all the USB transfers. Just look at the logs from the Windows > sniffer and from usbmon, and see what the two systems do differently. > Maybe Windows ignores the value in the descriptor and polls at > intervals of 1 ms; then the 17x behavior might still be present but it > would be undetectable. Just in case it becomes useful for future reference, I found this link: http://msdn.microsoft.com/en-us/library/ms793346.aspx It describes the USB_ENDPOINT_DESCRIPTOR structure for Windows drivers. It defines the polling interval for bInterval values for low, full and high speed devices. In this case, high speed devices for 6 <= bInterval <= 255 have a polling interval of 32 uframes or 4ms. With the 17x delay this becomes 68ms which is close to the 90ms I was seeing from usb sniffs (as you mentioned, they may not be that accurate). Thanks for your help, I'll continue looking in to the firmware issues... Stuart -- 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
