linux-kernel - Re: [PATCH v6 06/10] drm/display/hdmi: implement hotplug functions

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Message-ID: <bapkgt2e33bhdmun4efcuaedshyyv7qvjgugu5y53ordw3gigl@n7zbfoga7qo7>
Date: Mon, 16 Dec 2024 19:55:57 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Maxime Ripard <mripard@...nel.org>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
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Subject: Re: [PATCH v6 06/10] drm/display/hdmi: implement hotplug functions

On Mon, Dec 16, 2024 at 06:20:04PM +0100, Maxime Ripard wrote:
> On Fri, Dec 06, 2024 at 12:16:00PM +0200, Dmitry Baryshkov wrote:
> > The HDMI Connectors need to perform a variety of tasks when the HDMI
> > connector state changes. Such tasks include setting or invalidating CEC
> > address, notifying HDMI codec driver, updating scrambler data, etc.
> > 
> > Implementing such tasks in a driver-specific callbacks is error prone.
> > Start implementing the generic helper function (currently handling only
> > the HDMI Codec framework) to be used by drivers utilizing HDMI Connector
> > framework.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> >  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 61 +++++++++++++++++++++++++
> >  include/drm/display/drm_hdmi_state_helper.h     |  8 ++++
> >  2 files changed, 69 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > index 80bf2829ba89b5f84fed4fa9eb1d6302e10a4f9e..4cdeb63688b9e48acd8e8ae87a45b6253f7dd12b 100644
> > --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > @@ -769,3 +769,64 @@ drm_atomic_helper_connector_hdmi_clear_audio_infoframe(struct drm_connector *con
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_clear_audio_infoframe);
> > +
> > +/**
> > + * drm_atomic_helper_connector_hdmi_hotplug_edid - Handle the hotplug event for the HDMI connector passing custom EDID
> > + * @connector: A pointer to the HDMI connector
> > + * @status: Connection status
> > + * @drm_edid: EDID to process
> > + *
> > + * This function should be called as a part of the .detect() / .detect_ctx()
> > + * and .force() callbacks, updating the HDMI-specific connector's data. Most
> > + * drivers should be able to use @drm_atomic_helper_connector_hdmi_hotplug()
> > + * instead.
> > + *
> > + * Returns:
> > + * Zero on success, error code on failure.
> > + */
> > +int
> > +drm_atomic_helper_connector_hdmi_hotplug_edid(struct drm_connector *connector,
> > +					      enum drm_connector_status status,
> > +					      const struct drm_edid *drm_edid)
> > +{
> > +	if (status == connector_status_disconnected) {
> > +		// TODO: also handle CEC and scramber, HDMI sink disconnected.
> > +		drm_connector_hdmi_codec_plugged_notify(connector, false);
> > +	}
> > +
> > +	drm_edid_connector_update(connector, drm_edid);
> > +
> > +	if (status == connector_status_connected) {
> > +		// TODO: also handle CEC and scramber, HDMI sink is now connected.
> > +		drm_connector_hdmi_codec_plugged_notify(connector, true);
> > +	}
> > +
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_hotplug_edid);
> 
> I think we discussed it in a previous version's thread after you sent
> that one, but I'd rather have that helper call an edid retrieval
> function than passing it edids.

Ack, I forgot to add the hook. I'll do that for the next version. I'll
add the .read_edid callback to the HDMI functions.

> 
> Also, EDIDs are mandatory for HDMI, so I'd call the function
> drm_atomic_helper_connector_hdmi_hotplug.

See below.

> 
> > +/**
> > + * drm_atomic_helper_connector_hdmi_hotplug - Handle the hotplug event for the HDMI connector
> > + * @connector: A pointer to the HDMI connector
> > + * @status: Connection status
> > + *
> > + * This function should be called as a part of the .detect() / .detect_ctx()
> > + * and .force() callbacks, updating the HDMI-specific connector's data.
> > + *
> > + * Returns:
> > + * Zero on success, error code on failure.
> > + */
> > +int
> > +drm_atomic_helper_connector_hdmi_hotplug(struct drm_connector *connector,
> > +					 enum drm_connector_status status)
> > +{
> > +	const struct drm_edid *drm_edid;
> > +	int ret;
> > +
> > +	drm_edid = drm_edid_read(connector);
> > +	ret = drm_atomic_helper_connector_hdmi_hotplug_edid(connector, status, drm_edid);
> > +	drm_edid_free(drm_edid);
> 
> Oh. Why do we need the two variants? Or is it to deal with drivers that
> don't set connector->ddc?

Yes. There are enough HDMI bridge drivers that would provide the
callback instead of the DDC bus. Adding callback should solve that.

-- 
With best wishes
Dmitry