[PATCH v2 3/3] drm/edid: Implement SCDC Read Request capability detection

[Jose Abreu]

Hi Thierry,


Do you think while you are at it you could implement a
set_scrambling() callback? It should be pretty straight forward:
you read the SCDC_TMDS_CONFIG reg, do a mask, and then write it
again.


I think this is an important feature that we should have.


Best regards,

Jose Miguel Abreu


On 02-12-2016 19:24, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
>
> Sinks that support SCDC can optionally have the capability to initiate
> read requests, which are a mechanism by which a sink can notify its
> source that it should read the Update Flags. If either the sink or the
> source are not Read Request capable, polling of the Update Flags shall
> be employed.
>
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
> Changes in v2:
> - new patch
>
>  drivers/gpu/drm/drm_edid.c | 36 ++++++++++++++++++++++++++++++++++++
>  include/drm/drm_edid.h     |  1 +
>  2 files changed, 37 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 369961597ee5..8211cce3e09e 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3736,6 +3736,42 @@ bool drm_detect_hdmi_scdc(struct edid *edid)
>  EXPORT_SYMBOL(drm_detect_hdmi_scdc);
>  
>  /**
> + * drm_detect_hdmi_scdc_rr_capable - detect whether an HDMI sink is capable of
> + *    initiating an SCDC Read Request
> + * @edid: sink EDID information
> + *
> + * Parse the CEA extension according to CEA-861-B to find an HF-VSDB as
> + * defined in HDMI 2.0, section 10.3.2 "HDMI Forum Vendor Specific Data
> + * Block" and checks if the RR_Capable bit (bit 6 of byte 6) is set.
> + *
> + * Returns:
> + * True if the sink is capable of initiating an SCDC Read Request, false
> + * otherwise.
> + */
> +bool drm_detect_hdmi_scdc_rr_capable(struct edid *edid)
> +{
> +	unsigned int start, end, i;
> +	const u8 *cea;
> +
> +	cea = drm_find_cea_extension(edid);
> +	if (!cea)
> +		return false;
> +
> +	if (cea_db_offsets(cea, &start, &end))
> +		return false;
> +
> +	for_each_cea_db(cea, i, start, end) {
> +		if (cea_db_is_hdmi_forum_vsdb(&cea[i])) {
> +			if (cea[i + 6] & 0x40)
> +				return true;
> +		}
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(drm_detect_hdmi_scdc_rr_capable);
> +
> +/**
>   * drm_detect_monitor_audio - check monitor audio capability
>   * @edid: EDID block to scan
>   *
> diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
> index 7ea7e90846d8..d1c29586035e 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -441,6 +441,7 @@ u8 drm_match_cea_mode(const struct drm_display_mode *to_match);
>  enum hdmi_picture_aspect drm_get_cea_aspect_ratio(const u8 video_code);
>  bool drm_detect_hdmi_monitor(struct edid *edid);
>  bool drm_detect_hdmi_scdc(struct edid *edid);
> +bool drm_detect_hdmi_scdc_rr_capable(struct edid *edid);
>  bool drm_detect_monitor_audio(struct edid *edid);
>  bool drm_rgb_quant_range_selectable(struct edid *edid);
>  int drm_add_modes_noedid(struct drm_connector *connector,