[Bug 217089] xone23c mixer

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=217089

--- Comment #15 from Alan Stern (stern@rowland.harvard.edu) ---
The two usbmon traces show a big difference right near the start.  You can
check my analysis by doing:

   cat /sys/module/usbcore/parameters/old_scheme_first

under each of the kernels.  My guess is that the file contains Y in the -33
kernel and N in the -37 kernel.

That setting should not make any difference to a reasonable device.  But
apparently the Xone isn't reasonable, and it changes its behavior based on this
parameter setting.  Technically, it removes the second configuration when it is
reset a second time after being plugged in.  The -37 usbmon trace shows that
the xone reports two configs after the first reset and only one after the
second reset.  The relevant lines from the trace, right after the first reset,
are:

ffff8bfede5c8900 121253611 S Ci:1:000:0 s 80 06 0100 0000 0040 64 <
ffff8bfede5c8900 121253721 C Ci:1:000:0 0 18 = 12010002 ef020140 f0220800
00020102 0302

The 02 at the end is the number of configurations.

ffff8bfede5c8900 121253739 S Co:1:001:0 s 23 03 0004 0001 0000 0
ffff8bfede5c8900 121253750 C Co:1:001:0 0 0
ffff8bfede5c8900 121321750 S Ci:1:001:0 s a3 00 0000 0001 0004 4 <
ffff8bfede5c8900 121321766 C Ci:1:001:0 0 4 = 03051000
ffff8bfede5c8900 121321771 S Co:1:001:0 s 23 01 0014 0001 0000 0
ffff8bfede5c8900 121321786 C Co:1:001:0 0 0

Those lines are the second reset.

ffff8bfede5c8900 121401578 S Ci:1:007:0 s 80 06 0100 0000 0012 18 <
ffff8bfede5c8900 121401685 C Ci:1:007:0 0 18 = 12010002 ef020140 f0220800
00020102 0301

Here the 02 at the end has changed to 01.  The -33 trace shows only one reset,
and the number of configs doesn't change from 2 to 1.

Assuming this is true, the good news is that the parameter is something you can
easily change.  Just do (as root):

   echo Y >/sys/module/usbcore/parameters/old_scheme_first

under the -37 kernel and then see what happens when you plug in the device.

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