On Thu, Mar 29, 2012 at 10:52 AM, Johannes Stezenbach wrote: > On Wed, Mar 28, 2012 at 11:28:46PM +0200, Peter Stuge wrote: >> Sarah Sharp wrote: >> > Here is the other mail I was referring to in the thread with shashank. >> > >> > Alan, perhaps there's a change from 2.6.38 to 3.0 that makes the USB >> > core request a string descriptor that the USB devices don't like? >> > >> > On Tue, Mar 27, 2012 at 08:23:03PM +0530, Aditya Mittal wrote: >> > > We see a request for string descriptor 238 (0xEE) which is a microsoft >> > > specific descriptor with kernel 3.0.0 whereas we do not see a request for >> > > this string descriptor for version 2.6.38. >> >> Interesting. The 0xee string is indeed a Microsoft USB extension. It >> can be used to tell Windows what driver it should use for the device. >> Works really well out of the box on Windows 8 and later. >> >> I'm also surprised if Linux is sending that. I'm not saying that it's >> wrong, just surprised. In any case, any device *must* be able to deal >> with a request for a string descriptor which doesn't exist. >> >> This is clearly a problem in the device, regardless of where the 0xee >> request is coming from. (Wild guess: virtual machine someone forgot >> was still running?) Windows XPSP1 and later ask exactly once for the >> string descriptor, for every device that hasn't been seen before. > > AFAIK the 0xee is not sent by Linux kernel, it is sent by mtp-probe > (part of libmtp, media transfer protocol) which is run via udev rule. > I'm not sure why there is a difference between Linux 3.0.0 and 2.6.38? Yes, it is done here: http://libmtp.git.sourceforge.net/git/gitweb.cgi?p=libmtp/libmtp;a=blob;f=src/libusb-glue.c;h=0b22369cd333ca21be9cdea8e40a7dc032ab4b72;hb=HEAD#l380 And it does ask for a string descriptor using a length of 1024, so that answers my previous question. Maybe the udev rule in question uses some attributes that will match on some kernel versions and not on others. Tormod -- 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
