linux-kernel - Re: [PATCH v3 01/10] drm/connector: add CEC-related fields

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Message-ID: <20250205-strong-azure-koel-f5b1f1@houat>
Date: Wed, 5 Feb 2025 15:28:51 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Dave Stevenson <dave.stevenson@...pberrypi.com>, 
	Maíra Canal <mcanal@...lia.com>, Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/10] drm/connector: add CEC-related fields

On Tue, Jan 28, 2025 at 03:12:41PM +0200, Dmitry Baryshkov wrote:
> On Tue, Jan 28, 2025 at 11:33:05AM +0100, Maxime Ripard wrote:
> > On Sun, Jan 26, 2025 at 03:29:06PM +0200, Dmitry Baryshkov wrote:
> > > As a preparation to adding HDMI CEC helper code, add CEC-related fields
> > > to the struct drm_connector. Include both cec_adapter and cec_notifier,
> > > allowing drivers to select which one to use. The unregister callback
> > > is provided to let drivers unregister CEC-related data in a generic way
> > > without polluting drm_connector.c with dependencies on the CEC
> > > functions.
> > > 
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > > ---
> > >  drivers/gpu/drm/drm_connector.c | 13 ++++++++++++
> > >  include/drm/drm_connector.h     | 44 +++++++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 57 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > > index 1383fa9fff9bcf31488453e209a36c6fe97be2f1..fffb718b09eaaac200e6abc7524bbfe98c4741f4 100644
> > > --- a/drivers/gpu/drm/drm_connector.c
> > > +++ b/drivers/gpu/drm/drm_connector.c
> > > @@ -279,6 +279,7 @@ static int drm_connector_init_only(struct drm_device *dev,
> > >  	INIT_LIST_HEAD(&connector->probed_modes);
> > >  	INIT_LIST_HEAD(&connector->modes);
> > >  	mutex_init(&connector->mutex);
> > > +	mutex_init(&connector->cec.mutex);
> > >  	mutex_init(&connector->eld_mutex);
> > >  	mutex_init(&connector->edid_override_mutex);
> > >  	mutex_init(&connector->hdmi.infoframes.lock);
> > > @@ -698,6 +699,16 @@ static void drm_mode_remove(struct drm_connector *connector,
> > >  	drm_mode_destroy(connector->dev, mode);
> > >  }
> > >  
> > > +static void drm_connector_cec_unregister(struct drm_connector *connector)
> > > +{
> > > +	mutex_lock(&connector->cec.mutex);
> > > +
> > > +	if (connector->cec.funcs->unregister)
> > > +		connector->cec.funcs->unregister(connector);
> > > +
> > > +	mutex_unlock(&connector->cec.mutex);
> > > +}
> > > +
> > >  /**
> > >   * drm_connector_cleanup - cleans up an initialised connector
> > >   * @connector: connector to cleanup
> > > @@ -718,6 +729,8 @@ void drm_connector_cleanup(struct drm_connector *connector)
> > >  
> > >  	platform_device_unregister(connector->hdmi_audio.codec_pdev);
> > >  
> > > +	drm_connector_cec_unregister(connector);
> > > +
> > 
> > This should either be in a separate patch, or mentioned in the commit title/log
> 
> I'll mention it in the commit message.
> 
> > 
> > >  	if (connector->privacy_screen) {
> > >  		drm_privacy_screen_put(connector->privacy_screen);
> > >  		connector->privacy_screen = NULL;
> > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > > index f13d597370a30dc1b14c630ee00145256052ba56..6da840673b1209c84bbc396643c6033679a7ec74 100644
> > > --- a/include/drm/drm_connector.h
> > > +++ b/include/drm/drm_connector.h
> > > @@ -46,6 +46,7 @@ struct drm_property_blob;
> > >  struct drm_printer;
> > >  struct drm_privacy_screen;
> > >  struct drm_edid;
> > > +struct cec_adapter;
> > >  struct edid;
> > >  struct hdmi_codec_daifmt;
> > >  struct hdmi_codec_params;
> > > @@ -1191,6 +1192,19 @@ struct drm_connector_hdmi_audio_funcs {
> > >  			   bool enable, int direction);
> > >  };
> > >  
> > > +/**
> > > + * struct drm_connector_cec_funcs - drm_hdmi_connector control functions
> > > + */
> > > +struct drm_connector_cec_funcs {
> > > +	/**
> > > +	 * @adap_unregister: unregister CEC adapter / notifier.
> > > +	 *
> > > +	 * The callback to unregister CEC adapter or notifier, so that the core
> > > +	 * DRM layer doesn't depend on the CEC_CORE.
> > > +	 */
> > > +	void (*unregister)(struct drm_connector *connector);
> > > +};
> > > +
> > >  /**
> > >   * struct drm_connector_hdmi_funcs - drm_hdmi_connector control functions
> > >   */
> > > @@ -1832,6 +1846,31 @@ struct drm_connector_hdmi {
> > >  	} infoframes;
> > >  };
> > >  
> > > +/**
> > > + * struct drm_connector_cec - DRM Connector CEC-related structure
> > > + */
> > > +struct drm_connector_cec {
> > > +	/**
> > > +	 * @mutex: protects all CEC-related fields
> > > +	 */
> > 
> > All fields? Which fields require to be protected by a specific mutex
> > here?
> 
> Yes, all the fields. adapter, notifier and funcs are all protected by
> the mutex. See the drm_connector_cec_unregister() implementation (and
> corresponding unregister() callbacks implementations.

That's still surprising to me. Like, what concurrency source / code path
will need to make sure funcs is updated properly? or the adapter and
notifier?

Maxime

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