Messages in this thread | | | Date | Thu, 21 Feb 2013 13:10:16 +0100 | From | Daniel Mack <> | Subject | Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers |
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On 21.02.2013 10:03, Takashi Iwai wrote: > At Thu, 21 Feb 2013 01:55:50 +0000, > Pawel Moll wrote: >> >> 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> >> --- >> include/uapi/linux/usb/audio.h | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h >> index ac90037..d2314be 100644 >> --- a/include/uapi/linux/usb/audio.h >> +++ b/include/uapi/linux/usb/audio.h >> @@ -384,14 +384,16 @@ static inline __u8 uac_processing_unit_iProcessing(struct uac_processing_unit_de >> 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; >> } > > Looks good to me. > > An alternative would be to change uac_processing_unit_bControlSize() > to correct the header size, but I don't think it's good, as > bControlSize fields in other units show the value including the header > size. > > Daniel, what do you think?
Looks good to me too. and this should be marked for stable of course.
Thanks for fixing this, Pawell!
Daniel
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