[PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers

[PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers

[Pawel Moll]

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;
 }
 
 /* 4.5.2 Class-Specific AS Interface Descriptor */
-- 
1.7.10.4

Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers

[Takashi Iwai]

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?


thanks,

Takashi

Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers

[Daniel Mack]

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

Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers

[Takashi Iwai]

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