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Re: kern/46696: uhub disables port where USB keyboard attached

The following reply was made to PR kern/46696; it has been noted by GNATS.

From: Andreas Gustafsson <>
Subject: Re: kern/46696: uhub disables port where USB keyboard attached
Date: Sat, 15 Sep 2012 16:40:05 +0300

 Mike, Matthias,
 I have now identified the commit where kern/46696 appeared (on my
 machine, at least) by means of a semi-automated binary search.  It was
 src/sys/dev/usb/usb_subr.c 1.172, committed by Matthias more than two
 years ago:
   revision 1.172
   date: 2010/07/20 20:56:06;  author: drochner;  state: Exp;  lines: +43 -14
   another iteration in the eternal device enumeration struggle:
   use a request of 64 bytes for the initial device descriptor fetch.
   This is what windows does, and I've seen USB device firmware which
   really depends on this. (sends 8 bytes if 64 are requested and
   the full descriptor which is more than NetBSD's USB_MAX_IPACKET
   otherwise) This is the world...
 For testing, I have prepared a patch which effectively reverts this commit:
 Mike, can you try this patch and see if it fixes the problem for you?
 Matthias, can you identify the USB device that prompted the above
 commit?  And if it is a full-speed device, would it be possible
 to use the 64-byte request size for full-speed devices but not
 low-speed ones?
 Andreas Gustafsson,

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