Commit 99fc86450c "ALSA: usb-mixer:
parse descriptors with structs" introduced a set of useful parsers
for descriptors. Unfortunately the parses for the Processing Unit
Descriptor came with a very subtle bug...
Functions uac_processing_unit_iProcessing() and
uac_processing_unit_specific() were indexing the baSourceID array
forgetting the fields before the iProcessing and process-specific
descriptors.
The problem was observed with Sound Blaster Extigy mixer,
where nNrModes in Up/Down-mix Processing Unit Descriptor
was accessed at offset 10 of the descriptor (value 0)
instead of offset 15 (value 7). In result the resulting
control had interesting limit values:
Simple mixer control 'Channel Routing Mode Select',0
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - -1
Mono: -1 [100%]
Fixed by starting from the bmControls, which was calculated
correctly, instead of baSourceID.
Now the mentioned control is fine:
Simple mixer control 'Channel Routing Mode Select',0
Capabilities: volume volume-joined penum
Playback channels: Mono
Capture channels: Mono
Limits: 0 - 6
Mono: 0 [0%]
Signed-off-by: Pawel Moll <mail@pawelmoll.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
b531f81b0d