[alsa-devel] Per board ucm files on x86?

[Takashi Iwai]

On Mon, 11 Dec 2017 22:25:22 +0100,
Hans de Goede wrote:
> 
> Hi,
> 
> On 11-12-17 14:40, Takashi Iwai wrote:
> > On Mon, 11 Dec 2017 13:30:35 +0100,
> > Hans de Goede wrote:
> >>
> >> Hi All,
> >>
> >> This weekend I've created a modified ucm config based on:
> >>
> >> https://github.com/plbossart/UCM/tree/master/chtrt5645
> >>
> >> For a board which has a single speaker connected to the
> >> left channel (standard mono speaker setup) and a stereo
> >> headphone jack with working jack detection.
> >>
> >> I've been unable to come up with a ucm file which allows
> >> selecting between a "Stereo Speaker + Headphone" vs
> >> "Mono Speaker + Headphone" output profile.
> >>
> >> https://github.com/plbossart/UCM/tree/master/byt-rt5640
> >> has "Mono Speaker", "Stereo Speaker" and "Headphone"
> >> profiles but does not auto-switch between Headphone
> >> and speaker based on jack detection, I've been unable to
> >> allow selecting either stereo or mono speaker while
> >> keeping auto-switching to/from the headphones.
> >>
> >> But thinking more about this I don't think that having
> >> "Stereo Speaker + Headphone" and "Mono Speaker + Headphone"
> >> profiles is the answer. Profiles make sense on machines with
> >> a bunch of outputs where we don't no what the user is going
> >> to plug in, but in this case the stereo vs mono speaker
> >> distinction is a clear property of the device, which we
> >> should IMHO autodetect based on the device-model.
> >>
> >> So I think we need a way to have different ucm files per board,
> >> so instead of loading /usr/share/ucm/chtrt5645/*.conf on my
> >> device, alsa should try to load /usr/share/ucm/chtrt5645-<boardname>/*.conf
> >>
> >> Specifically I'm thinking about using udev + hwdb (dmi string)
> >> matching to set an ALSA_UCM_NAME udev property.
> >>
> >> If the consensus is that this is a good idea I can take a shot
> >> at writing patches for this (in my spare time mostly), the
> >> downside of this approach is it would cause a dependency on
> >> libudev for the alsa ucm code.
> >
> > You don't need to patch, I guess.  The recent code should set a string
> > generated from DMI as the longname of the card, and alsa-lib UCM
> > parser prefers the longname to the driver name field.  That is,
> > /usr/share/ucm/$LONGNAME/$LONGNAME.conf would be read at first, then
> > /usr/share/ucm/$DRIVER/$DRIVER.conf is used as fallback.
> 
> I'm afraid this does not work entirely as one would expect, after
> opening /usr/share/ucm/$LONGNAME/$LONGNAME.conf which contains:
> 
> SectionUseCase."HiFi" {
>         File "HiFi.conf"
>         Comment "Default"
> }
> 
> strace shows that alsa-lib opens:
> /usr/share/ucm/$DRIVER/HiFi.conf and to get it to load the HiFi.conf
> under /usr/share/ucm/$LONGNAME I need to do:
> 
> SectionUseCase."HiFi" {
>         File "../gpd-win-pocket-rt5645/HiFi.conf"
>         Comment "Default"
> }
> 
> Leading to the following in strace:
> 
> openat(AT_FDCWD, "/usr/share/alsa/ucm/chtrt5645/../gpd-win-pocket-rt5645/HiFi.conF", O_RDONLY) = 23
> 
> Which to me seems undesirable behavior by alsa-lib.

It must be a bug in the code.  It's supposed to read from $LONGNAME
directory.  Mengdong?


Takashi