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Commit b531f81b0d70ffbe8d70500512483227cc532608

Authored by Pawel Moll
Committed by Takashi Iwai
1 parent 92c69e796b
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

ALSA: usb: Fix Processing Unit Descriptor parsers 

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 <mail@pawelmoll.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Showing 1 changed file with 4 additions and 2 deletions Side-by-side Diff

include/uapi/linux/usb/audio.h
Diff comments   View file @ b531f81
... ... @@ -384,14 +384,16 @@
384 384 int protocol)
385 385 {
386 386 __u8 control_size = uac_processing_unit_bControlSize(desc, protocol);
387   - return desc->baSourceID[desc->bNrInPins + control_size];
  387 + return *(uac_processing_unit_bmControls(desc, protocol)
  388 + + control_size);
388 389 }
389 390  
390 391 static inline __u8 *uac_processing_unit_specific(struct uac_processing_unit_descriptor *desc,
391 392 int protocol)
392 393 {
393 394 __u8 control_size = uac_processing_unit_bControlSize(desc, protocol);
394   - return &desc->baSourceID[desc->bNrInPins + control_size + 1];
  395 + return uac_processing_unit_bmControls(desc, protocol)
  396 + + control_size + 1;
395 397 }
396 398  
397 399 /* 4.5.2 Class-Specific AS Interface Descriptor */