[alsa-devel] Resend: Incorrect sbits for snd-usb-audio

[Takashi Iwai]

At Sun, 8 Dec 2013 12:47:31 -0600,
Sander Jansen wrote:
> 
> [1  <text/plain; UTF-8 (7bit)>]
> On Sun, Dec 8, 2013 at 12:27 PM, Sander Jansen <s.jansen at gmail.com> wrote:
> 
> >
> >
> > On Sun, Dec 8, 2013 at 3:20 AM, Takashi Iwai <tiwai at suse.de> wrote:
> >
> >> At Fri, 6 Dec 2013 14:57:46 -0600,
> >> Sander Jansen wrote:
> >> >
> >> > Hi,
> >> >
> >> > I had send this out earlier back in September, but never got a response.
> >> >
> >> > I have a Focusrite Scarlett 2i4 USB Audio Interface. The audio format
> >> > exposed by ALSA for  this device is S32_LE. From the hardware specs and
> >> > lsusb. it supposed to only have a 24 bit resolution (with the LSB bits
> >> set
> >> > to 0):
> >> >
> >> > AudioStreaming Interface Descriptor:
> >> >         bLength                 6
> >> >         bDescriptorType        36
> >> >         bDescriptorSubtype      2 (FORMAT_TYPE)
> >> >         bFormatType             1 (FORMAT_TYPE_I)
> >> >         bSubslotSize            4
> >> >         bBitResolution         24
> >> >
> >> > When I query the sbits for this device, I expect it to return 24, but
> >> > instead it returns 32. Looking through the usb audio driver code, it
> >> > doesn't look like this information is actually exposed to userspace. The
> >> > 'parse_audio_format_i_type'  in usb/format.c merely returns the
> >> supported
> >> > formats, but doesn't include any msbits info. (and it doesn't look like
> >> it
> >> > can be easily changed to return the msbits info as well).
> >> >
> >> > Was this intentionally left out, or is this a missing feature in the
> >> driver?
> >>
> >> It's just because of laziness because almost no applications check the
> >> msbit but only the format type.  Feel free to send an enhancement
> >> patch.
> >>
> >>
> >>
> > Thanks for the clarification. I may give that a shot.
> >
> > Sander
> >
> >
> Forgive my ignorance, but to which git tree should this patch be developed
> on?
> 
> git://git.alsa-project.org/alsa-kernel.git
> https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/
> ?

The latter, at best against for-next branch of sound.git tree.


Takashi