Messages in this thread | | | Date | Thu, 21 Feb 2013 14:20:19 +0100 | From | Takashi Iwai <> | Subject | Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers |
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At Thu, 21 Feb 2013 13:10:16 +0100, Daniel Mack wrote: > > 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!
OK, applied now. Thanks.
Takashi
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