Re: [PATCH 1/2] ALSA: hda/hdmi: Add helper function to check if a device is HDMI codec

Takashi Iwai
2023-11-28T10:48:13Z

On Tue, 28 Nov 2023 11:16:00 +0100,
Péter Ujfalusi wrote:
>
>
>
> On 28/11/2023 12:02, Takashi Iwai wrote:
> > On Tue, 28 Nov 2023 10:53:56 +0100,
> > Péter Ujfalusi wrote:
> >>
> >>
> >>
> >> On 28/11/2023 11:39, Takashi Iwai wrote:
> >>> Hm... I still find it's a bad move to use an exported symbol from
> >>> another codec driver.
> >>
> >> The other option is to check for 0x4 (or address 2), but I'm not sure if
> >> this is Intel only or universally true for HDMI codecs.
> >>
> >>> And, I wonder what if you have a system that has only one HDMI codec
> >>> without analog one? Would it still work with your change?
> >>
> >> Yes, it works with only HDMI codec (for example on SoundWire laptops) or
> >> with UP2 board which only have HDMI audio support by default.
> >
> > Interesting. With your patch 2, hdac_hda_hdmi_codec is without the
> > DAPM definitions, and even if that's the only one that is registered,
> > it will still work? So it means that it works without DAPM
> > definitions at all?
>
> Well, it is a bit more 'interesting' from that angle.
> for patch two we needed:
> https://lore.kernel.org/linux-sound/20231124124015.15878-1-peter.ujfalusi@linux.intel.com/

Ouch, this kind of information has to be mentioned in the patch
description. Otherwise one would take only this series and face a
problem easily. I can imagine such a problem on the stable tree.

> The reason is that prior to patch 2 the analog codec would create the
> DAPM widgets for the HDMI also and the DAPM route would be available but
> the HDMI would still not work:
> we had PCMs for HDMI but non operational ones.
>
> If we had a codec+HDMI then we would have the warnings that the second
> codec is registering the same DAPM widgets again.
>
> With the linked patch plus this series we will not register the DAPM
> widgets and the machine driver would drop the routes.
> The PCMs will be still created and they will be still non functional but
> we will have no warning when the system have two codecs.
>
> The core HDA+patch_hdmi is needed for the hdac_hda to have working HDMI
> audio, but the patch init is after the codec driver's probe:
>
> # dmesg | grep peter
> [ 4088.698111] [peter] hdac_hda_dev_probe: is_hdmi_codec(): 0
> [ 4088.698112] [peter] hdac_hda_dev_probe: hdev->is_hdmi: 0
> [ 4088.698114] [peter] hdac_hda_dev_probe: snd_hda_device_is_hdmi(): 1
> [ 4088.862882] [peter] patch_i915_tgl_hdmi: ENTER
> [ 4088.862886] [peter] alloc_intel_hdmi: ENTER
> [ 4088.872269] [peter] generic_hdmi_build_pcms: ENTER
> [ 4088.872279] [peter] hdac_hda_codec_probe: is_hdmi_codec(): 1
>
> We need to know if the codec is HDMI or not in hdac_hda_dev_probe()
>
> I would rather not risk to move the hdac_hda as Intel only using address
> 2 as HDMI indication - which I'm still not sure if it is Intel only or
> generic HDA convention.

Sure, it doesn't sound right, either.

Can we then add DAPM widgets and routes later conditionally instead of
having it in component driver definition?

Takashi