[PATCH v8 04/39] drm/connector: Add HDMI 2.0 scrambler infrastructure

[Dmitry Baryshkov]

On Thu, Jul 02, 2026 at 05:46:17PM +0300, Cristian Ciocaltea wrote:
> Add the connector-level infrastructure to support HDMI 2.0 scrambling:
> 
> - A scrambler_supported flag to indicate whether the source supports the
>   scrambling capability, in which case the newly introduced
>   .scrambler_{enable|disable}() callbacks in drm_connector_hdmi_funcs
>   are mandatory

Do we need a flag? What would it mean if the flag is set, but the
callbacks are not? Can we drop the flag and use the presence of the
callbacks as a way to identify that scrambler is enabled?

> - A scrambler_needed flag to be managed by the hdmi state helpers based
>   on the negotiated TMDS character rate and the source/sink scrambling
>   capabilities
> - A scrambler_enabled flag to track whether scrambling is currently
>   active
> - A delayed work item (scdc_work) with an associated callback (scdc_cb)
>   to monitor sink-side scrambling status and retry the setup if the sink
>   resets it
> 
> These are intended to be used by SCDC scrambling helpers to coordinate
> scrambling setup and teardown between the source driver and the DRM
> core.
> 
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 26 ++++++++++++--
>  include/drm/drm_connector.h     | 77 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 100 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index c7ce6b7bd8b0..deecfc582f09 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -220,6 +220,19 @@ void drm_connector_free_work_fn(struct work_struct *work)
>  	}
>  }
>  
> +static void drm_connector_hdmi_scdc_work(struct work_struct *work)
> +{
> +	struct drm_connector *connector;
> +	struct drm_connector_hdmi *hdmi;
> +
> +	hdmi = container_of(to_delayed_work(work), struct drm_connector_hdmi,
> +			    scdc_work);
> +	connector = container_of(hdmi, struct drm_connector, hdmi);
> +
> +	if (hdmi->scdc_cb)
> +		hdmi->scdc_cb(connector);
> +}
> +
>  static int drm_connector_init_only(struct drm_device *dev,
>  				   struct drm_connector *connector,
>  				   const struct drm_connector_funcs *funcs,
> @@ -285,6 +298,7 @@ static int drm_connector_init_only(struct drm_device *dev,
>  	mutex_init(&connector->edid_override_mutex);
>  	mutex_init(&connector->hdmi.infoframes.lock);
>  	mutex_init(&connector->hdmi_audio.lock);
> +	INIT_DELAYED_WORK(&connector->hdmi.scdc_work, drm_connector_hdmi_scdc_work);
>  	connector->edid_blob_ptr = NULL;
>  	connector->epoch_counter = 0;
>  	connector->tile_blob_ptr = NULL;
> @@ -624,12 +638,18 @@ int drmm_connector_hdmi_init_with_caps(struct drm_device *dev,
>  	 * inferred limit with the actual controller capability. A value of
>  	 * zero keeps the default limit inferred from supported_hdmi_ver.
>  	 */

Here we need to check that the driver doesn't set only one callback of
the pair.

> -	if (caps->supported_hdmi_ver >= HDMI_VERSION_2_0)
> +	if (caps->supported_hdmi_ver >= HDMI_VERSION_2_0) {
> +		if (!hdmi_funcs->scrambler_enable ||
> +		    !hdmi_funcs->scrambler_disable)
> +			return -EINVAL;
> +
> +		connector->hdmi.scrambler_supported = true;
>  		connector->hdmi.max_tmds_char_rate = HDMI_2_0_TMDS_CHAR_RATE_MAX_HZ;
> -	else if (caps->supported_hdmi_ver >= HDMI_VERSION_1_3)
> +	} else if (caps->supported_hdmi_ver >= HDMI_VERSION_1_3) {
>  		connector->hdmi.max_tmds_char_rate = HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ;
> -	else if (caps->supported_hdmi_ver >= HDMI_VERSION_1_0)
> +	} else if (caps->supported_hdmi_ver >= HDMI_VERSION_1_0) {
>  		connector->hdmi.max_tmds_char_rate = HDMI_1_0_TMDS_CHAR_RATE_MAX_HZ;
> +	}
>  
>  	if (caps->max_tmds_char_rate) {
>  		if (caps->max_tmds_char_rate > connector->hdmi.max_tmds_char_rate)
> +
> +	/** @scdc_cb: Callback to be invoked as part of @scdc_work.
> +	 *
> +	 * Currently used to monitor sink-side scrambling status and retry
> +	 * setup if the sink resets it.
> +	 *
> +	 * This is assigned by the framework when making use of
> +	 * drm_connector_hdmi_enable_scrambling() helper.

No such helper. Also, please explain in the commit message, why do we
need to keep it configurable. Why the default is not enough?

> +	 */
> +	void (*scdc_cb)(struct drm_connector *connector);
> +
>  	/**
>  	 * @funcs: HDMI connector Control Functions
>  	 */
> 
> -- 
> 2.54.0
> 

-- 
With best wishes
Dmitry