On Wed, 22 Apr 2009, Stuart wrote: > 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. I don't know of any such information or tutorials. They would have to be very device-specific in any case, so probaby not of much use to you. > 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). Sure, submit a patch with your quirk to the HID maintainer. > 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). So the Windows EHCI driver has a lower maximum interval than the Linux driver does. It does explain your results. Good luck, Alan Stern -- 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
