[PATCH V2 2/2] drm/vc4: hdmi: Add jack detection to HDMI audio driver

[Dmitry Baryshkov]

On Thu, 6 Mar 2025 at 14:39, Maxime Ripard <mripard at kernel.org> wrote:
>
> Hi,
>
> On Tue, Mar 04, 2025 at 08:39:12PM +0100, Stefan Wahren wrote:
> > From: David Turner <david.turner at raspberrypi.com>
> >
> > Add ALSA jack detection to the vc4-hdmi audio driver so userspace knows
> > when to add/remove HDMI audio devices.
> >
> > Signed-off-by: David Turner <david.turner at raspberrypi.com>
> > Signed-off-by: Stefan Wahren <wahrenst at gmx.net>
> > ---
> >  drivers/gpu/drm/vc4/vc4_hdmi.c | 18 ++++++++++++++++++
> >  drivers/gpu/drm/vc4/vc4_hdmi.h |  7 +++++++
> >  2 files changed, 25 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> > index e4b027616d04..f46a135568b2 100644
> > --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> > @@ -51,6 +51,7 @@
> >  #include <linux/reset.h>
> >  #include <sound/dmaengine_pcm.h>
> >  #include <sound/hdmi-codec.h>
> > +#include <sound/jack.h>
> >  #include <sound/pcm_drm_eld.h>
> >  #include <sound/pcm_params.h>
> >  #include <sound/soc.h>
> > @@ -2203,6 +2204,22 @@ static const struct drm_connector_hdmi_audio_funcs vc4_hdmi_audio_funcs = {
> >       .shutdown = vc4_hdmi_audio_shutdown,
> >  };
> >
> > +static int vc4_hdmi_codec_init(struct snd_soc_pcm_runtime *rtd)
> > +{
> > +     struct vc4_hdmi *vc4_hdmi = snd_soc_card_get_drvdata(rtd->card);
> > +     struct snd_soc_component *component = snd_soc_rtd_to_codec(rtd, 0)->component;
> > +     int ret;
> > +
> > +     ret = snd_soc_card_jack_new(rtd->card, "HDMI Jack", SND_JACK_LINEOUT,
> > +                                 &vc4_hdmi->hdmi_jack);
> > +     if (ret) {
> > +             dev_err(rtd->dev, "HDMI Jack creation failed: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     return snd_soc_component_set_jack(component, &vc4_hdmi->hdmi_jack, NULL);
> > +}
> > +
> >  static int vc4_hdmi_audio_init(struct vc4_hdmi *vc4_hdmi)
> >  {
> >       const struct vc4_hdmi_register *mai_data =
> > @@ -2316,6 +2333,7 @@ static int vc4_hdmi_audio_init(struct vc4_hdmi *vc4_hdmi)
> >       dai_link->cpus->dai_name = dev_name(dev);
> >       dai_link->codecs->name = dev_name(&vc4_hdmi->connector.hdmi_audio.codec_pdev->dev);
> >       dai_link->platforms->name = dev_name(dev);
> > +     dai_link->init = vc4_hdmi_codec_init;
> >
> >       card->dai_link = dai_link;
> >       card->num_links = 1;
> > diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> > index e3d989ca302b..a31157c99bee 100644
> > --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> > +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> > @@ -4,6 +4,7 @@
> >  #include <drm/drm_connector.h>
> >  #include <media/cec.h>
> >  #include <sound/dmaengine_pcm.h>
> > +#include <sound/hdmi-codec.h>
> >  #include <sound/soc.h>
> >
> >  #include "vc4_drv.h"
> > @@ -211,6 +212,12 @@ struct vc4_hdmi {
> >        * KMS hooks. Protected by @mutex.
> >        */
> >       enum hdmi_colorspace output_format;
> > +
> > +     /**
> > +      * @hdmi_jack: Represents the connection state of the HDMI plug, for
> > +      * ALSA jack detection.
> > +      */
> > +     struct snd_soc_jack hdmi_jack;
> >  };
>
> It looks fairly generic to me. Is there any reason you didn't put it in
> the HDMI audio helpers?

I had a similar question in my mind, but after checking I also could
not find a good place for it. I had an idea of pushing this kind of
code to hdmi-codec.c / hdmi_probe(), but then I understood that it
might not work.
The codec can be registered independently from the platform sound card
device, the codec doesn't have a knowledge of the platform's data or
topology. We might not be able to specify the name (even through codec
platform data) if there are more than one HDMI connector / codec in
play.
So, I think that a sound card driver is a proper place for that (so it
belongs to the vc4 driver).



-- 
With best wishes
Dmitry