[alsa-devel] [PATCH v2] ALSA: x86: Select CONFIG_HDMI_LPE_AUDIO as default

[Ian W MORRISON]

On 20 March 2017 at 21:04, Takashi Iwai <tiwai at suse.de> wrote:

> On Mon, 20 Mar 2017 10:41:07 +0100,
> Ian W MORRISON wrote:
> >
> > On 20 March 2017 at 19:41, Takashi Iwai <tiwai at suse.de> wrote:
> >
> > > On Mon, 20 Mar 2017 09:17:30 +0100,
> > > Ian W MORRISON wrote:
> > > >
> > > > Oops ... forgot to copy alsa-devel and Pierre-Louis.
> > > >
> > > > On 20 March 2017 at 18:59, Takashi Iwai <tiwai at suse.de> wrote:
> > > >
> > > > > On Mon, 20 Mar 2017 08:42:32 +0100,
> > > > > Ian W MORRISON wrote:
> > > > > >
> > > > > > The upstream kernel builds for distributions such as Ubuntu
> which now
> > > > > > includes binary packages for v4.11 mainline kernel release
> > > candidates are
> > > > > > promoted as a way of testing upstream kernels to to confirm that
> > > upstream
> > > > > > has fixed a specific issue (see https://wiki.ubuntu.com/
> > > > > > Kernel/MainlineBuilds).
> > > > > >
> > > > > > Unfortunately the long awaited patch for providing HDMI audio
> > > support for
> > > > > > Bay Trail and Cherry Trail devices does not include this support
> > > through
> > > > > a
> > > > > > module built by default.
> > > > > >
> > > > > > Through including by default of the two associated CONFIG
> settings
> > > > > (SND_X86
> > > > > > and HDMI_LPE_AUDIO), upstream kernel builds would automatically
> > > provide
> > > > > the
> > > > > > much desired HDMI audio support by default.
> > > > > >
> > > > > > This patch uses a Kconfig 'default' statement to include the
> driver
> > > as
> > > > > > default.
> > > > > >
> > > > > > Changes in version 2: CONFIG_SND_X86 now a bool and changed
> default
> > > m to
> > > > > > default y
> > > > > >
> > > > > > Signed-off-by: Ian W Morrison <linuxium at linuxium.com.au>
> > > > > > ---
> > > > > >  sound/x86/Kconfig | 4 +++-
> > > > > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/sound/x86/Kconfig b/sound/x86/Kconfig
> > > > > > index 84c8f8fc..cac2270 100644
> > > > > > --- a/sound/x86/Kconfig
> > > > > > +++ b/sound/x86/Kconfig
> > > > > > @@ -1,6 +1,7 @@
> > > > > >  menuconfig SND_X86
> > > > > > -       tristate "X86 sound devices"
> > > > > > +       bool "X86 sound devices"
> > > > > >         depends on X86
> > > > > > +       default y
> > > > >
> > > > > This one is OK, but ...
> > > > >
> > > > > >         ---help---
> > > > > >           X86 sound devices that don't fall under SoC or PCI
> > > categories
> > > > > >
> > > > > > @@ -9,6 +10,7 @@ if SND_X86
> > > > > >  config HDMI_LPE_AUDIO
> > > > > >         tristate "HDMI audio without HDaudio on Intel Atom
> platforms"
> > > > > >         depends on DRM_I915
> > > > > > +       default y
> > > > >
> > > > > ... this is wrong.  Each driver config itself should be left
> > > > > unspecified.
> > > > >
> > > > > It's distributor's job to choose the right config here.
> > > > >
> > > > > Actually this goes back to one of my earlier points: A distributor
> > > doesn't
> > > > have to set 'HDMI' as HDMI audio is automatically provided.
> > >
> > > Provided by who...?
> > >
> >
> >
> > I suppose it is provided as a result of the architecture one runs the
> > primary Makefile on. With 'uname -m' returning 'x86_64' running 'make
> > defconfig' results in 'CONFIG_HDMI=y' being set so
> 'drivers/video/Makefile'
> > automatically makes 'drivers/video/hdmi.c' and as
> > 'arch/x86/configs/x86_64_defconfig' includes 'CONFIG_DRM=y' and
> > 'CONFIG_DRM_I915=y' and 'drivers/gpu/drm/i915/Makefile' makes
> > 'intel_audio.c'.
>
> The defconfig stuff supports only the limited device sets that are
> supposed to be very common.  Is HDMI_LPE_AUDIO classified really as
> such a thing?  I don't know...
>
>
In this instance I'd suggest that HDMI_LPE_AUDIO is common as without it
you do not get HDMI audio on all x86_64 devices. However see my comment
below.


>
> > > > This is just an
> > > > extension because by setting 'HDMI_LPE_AUDIO' the missing audio
> support
> > > for
> > > > BYT and CHT SoCs is then provided. Therefore, in this albeit unusual
> > > > instance, I reason is it appropriate to set HDMI_LPE_AUDIO so that
> audio
> > > is
> > > > automatically provided regardless of distribution. If a distributor
> > > didn't
> > > > want to allow audio for BYT and CHT SoC based devices running their
> > > distro
> > > > then they could always remove it from their distro specific config.
> > >
> > > It's a wrong approach.  What we're discussing about is just a
> > > configuration for a new individual driver, and the same rule should be
> > > applied to it like others.
> > >
> > > Check other drivers.  See whether default=y (or =m) is set to
> > > CONFIG_E1000E, as a random example.  With your argument, it should  be
> > > set to y or m as default, since the Ethernet functionality is already
> > > provided by the network core.
> > >
> > > In general, we don't set the default values to the driver configs
> > > unless there is a VERY specific reason to do so.
> > >
> > >
> > I'm trying to get HDMI audio by default for BYT & CHT SoC but currently
> > this requires 'CONFIG_HDMI_LPE_AUDIO' set with a value of 'm'. I don't
> want
> > to argue a 'special case' or promote a 'wrong approach' but just get HDMI
> > audio working so is there another way to achieve this?
>
> What's wrong with manually setting CONFIG_HDMI_LPE_AUDIO=m or =y?
> IOW, do all features on your CHT/BYT machines work without adjusting
> manually after defconfig?  If you have to do it in anyway, what makes
> it special for HDMI_LPD_AUDIO?
>
>
I've just tested various scenarios using a variety of devices with
v4.11-rc3. Having CONFIG_HDMI_LPE_AUDIO set by default is sufficient to get
audio on BYT/CHT devices over HDMI.

For example installing Ubuntu 16.04.2 on a BYT/CHT device, then upgrading
the kernel to v4.11-rc3 using the deb-binary from http://kernel.ubuntu.com/~
kernel-ppa/mainline/v4.11-rc3/ (an example of a current distro which is
compiling without setting CONFIG_HDMI_LPE_AUDIO) and there is no audio over
HDMI. Alternatively downloading v4.11-rc3 source, making defconfig,
manually setting CONFIG_HDMI_LPE_AUDIO, compiling and installing the
kernel on the BYT/CHT device will give you audio over HDMI.

If the BYT/CHT device has other sound cards (e.g accessed via a headphone
jack) then audio without setting CONFIG_HDMI_LPE_AUDIO may be possible
depending on the codec used and whether it is provided by default in the
kernel. So for example a Tronsmart Ara (CHT) device has audio over
headphones using the pre-compiled deb-binary above but no audio over HDMI.
Whereas with a (1st gen) Intel Compute Stick (BYT) device no audio is
possible using the pre-compiled deb-binary as the device only has an HDMI
port. To get sound you must therefore currently use a self-compiled kernel
with CONFIG_HDMI_LPE_AUDIO set.

Whilst Canonical may set CONFIG_HDMI_LPE_AUDIO to provide audio on BYT/CHT
devices by when is unknown and there is no guarantee they actually will.
This will be similar for all other distros with the worst case scenario
that no distributor adds CONFIG_HDMI_LPE_AUDIO to their configs resulting
in (arguably) little point including HDMI LPE audio support in the kernel.

I've laboured the point about 'BYT/CHT devices audio over HDMI' but to
answer your question completely there are other BYT/CHT devices (typically
tablets) that need a whole other bunch of patches to fix this and that.
They may need specialist kernel configs with specific settings but that is
a separate issue to the basic functional need of having audio over HDMI.

Does the above explanation justify my current approach or is there an
alternative that can be considered?


> > Would adding
> > 'CONFIG_HDMI_LPE_AUDIO=y' to 'arch/x86/configs/x86_64_defconfig' be
> another
> > mistake (assuming 'CONFIG_SND_X86' was set as per the first part of the
> > revised patch)? Would anyone even accept a patch
> > to 'arch/x86/configs/x86_64_defconfig' if this was acceptable?
>
> The content in x86_64_defconfig is another story, and it's maintained
> by x86 guys, so you can try it, of corse...
>
>
>
If I have exhausted the possibilities here I guess I'll have to go knocking
on their door.


> Takashi
> >
> >
> > >
> > > Takashi
> > >
>