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27 March 2024, 02:37:15 UTC
Revision 57e6dae1087bbaa6b33d3dd8a8e90b63888939a3 authored by Clemens Ladisch on 08 August 2013, 09:24:55 UTC, committed by Takashi Iwai on 08 August 2013, 09:37:34 UTC 
ALSA: usb-audio: do not trust too-big wMaxPacketSize values
 
The driver used to assume that the streaming endpoint's wMaxPacketSize
value would be an indication of how much data the endpoint expects or
sends, and compute the number of packets per URB using this value.

However, the Focusrite Scarlett 2i4 declares a value of 1024 bytes,
while only about 88 or 44 bytes are be actually used.  This discrepancy
would result in URBs with far too few packets, which would not work
correctly on the EHCI driver.

To get correct URBs, use wMaxPacketSize only as an upper limit on the
packet size.

Reported-by: James Stone <jamesmstone@gmail.com>
Tested-by: James Stone <jamesmstone@gmail.com>
Cc: <stable@vger.kernel.org> # 2.6.35+
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
1 parent ddb6b5a
History
Tip revision: 57e6dae1087bbaa6b33d3dd8a8e90b63888939a3 authored by Clemens Ladisch on 08 August 2013, 09:24:55 UTC
ALSA: usb-audio: do not trust too-big wMaxPacketSize values
Tip revision: 57e6dae
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