3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pawel Moll <m...@pawelmoll.com>
commit b531f81b0d70ffbe8d70500512483227cc532608 upstream.
Commit 99fc86450c439039d2ef88d06b222fd51a779176 "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 <m...@pawelmoll.com>
Signed-off-by: Takashi Iwai <ti...@suse.de>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
include/linux/usb/audio.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/include/linux/usb/audio.h
+++ b/include/linux/usb/audio.h
@@ -384,14 +384,16 @@ static inline __u8 uac_processing_unit_i
int protocol)
{
__u8 control_size = uac_processing_unit_bControlSize(desc, protocol);
- return desc->baSourceID[desc->bNrInPins + control_size];
+ return *(uac_processing_unit_bmControls(desc, protocol)
+ + control_size);
}
static inline __u8 *uac_processing_unit_specific(struct
uac_processing_unit_descriptor *desc,
int protocol)
{
__u8 control_size = uac_processing_unit_bControlSize(desc, protocol);
- return &desc->baSourceID[desc->bNrInPins + control_size + 1];
+ return uac_processing_unit_bmControls(desc, protocol)
+ + control_size + 1;
}
/* 4.5.2 Class-Specific AS Interface Descriptor */
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