Re: [Intel-gfx] [PATCH v2 13/15] drm/edid: add HF-EEODB support to EDID read and allocation

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jun 08, 2022 at 10:50:43AM +0300, Jani Nikula wrote:
> HDMI 2.1 section 10.3.6 defines an HDMI Forum EDID Extension Override
> Data Block, which may contain a different extension count than the base
> block claims. Add support for reading more EDID data if available. The
> extra blocks aren't parsed yet, though.
> 
> Hard-coding the EEODB parsing instead of using the iterators we have is
> a bit of a bummer, but we have to be able to do this on a partially
> allocated EDID while reading it.
> 
> v2:
> - Check for CEA Data Block Collection size (Ville)
> - Amend commit message and comment about hard-coded parsing
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/drm_edid.c | 89 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 86 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 77ec5b0e436d..5cac357e50b0 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -1581,6 +1581,15 @@ static bool version_greater(const struct drm_edid *drm_edid,
>  		(edid->version == version && edid->revision > revision);
>  }
>  
> +static int edid_hfeeodb_extension_block_count(const struct edid *edid);
> +
> +static int edid_hfeeodb_block_count(const struct edid *edid)
> +{
> +	int eeodb = edid_hfeeodb_extension_block_count(edid);
> +
> +	return eeodb ? eeodb + 1 : 0;
> +}
> +
>  static int edid_extension_block_count(const struct edid *edid)
>  {
>  	return edid->extensions;
> @@ -2026,6 +2035,11 @@ static struct edid *edid_filter_invalid_blocks(struct edid *edid,
>  	struct edid *new;
>  	int i, valid_blocks = 0;
>  
> +	/*
> +	 * Note: If the EDID uses HF-EEODB, but has invalid blocks, we'll revert
> +	 * back to regular extension count here. We don't want to start
> +	 * modifying the HF-EEODB extension too.
> +	 */
>  	for (i = 0; i < edid_block_count(edid); i++) {
>  		const void *src_block = edid_block_data(edid, i);
>  
> @@ -2235,7 +2249,7 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
>  				     size_t *size)
>  {
>  	enum edid_block_status status;
> -	int i, invalid_blocks = 0;
> +	int i, num_blocks, invalid_blocks = 0;
>  	struct edid *edid, *new;
>  	size_t alloc_size = EDID_LENGTH;
>  
> @@ -2277,7 +2291,8 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
>  		goto fail;
>  	edid = new;
>  
> -	for (i = 1; i < edid_block_count(edid); i++) {
> +	num_blocks = edid_block_count(edid);
> +	for (i = 1; i < num_blocks; i++) {
>  		void *block = (void *)edid_block_data(edid, i);
>  
>  		status = edid_block_read(block, i, read_block, context);
> @@ -2288,11 +2303,31 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
>  			if (status == EDID_BLOCK_READ_FAIL)
>  				goto fail;
>  			invalid_blocks++;
> +		} else if (i == 1) {
> +			/*
> +			 * If the first EDID extension is a CTA extension, and
> +			 * the first Data Block is HF-EEODB, override the
> +			 * extension block count.
> +			 *
> +			 * Note: HF-EEODB could specify a smaller extension
> +			 * count too, but we can't risk allocating a smaller
> +			 * amount.
> +			 */
> +			int eeodb = edid_hfeeodb_block_count(edid);
> +
> +			if (eeodb > num_blocks) {
> +				num_blocks = eeodb;
> +				alloc_size = edid_size_by_blocks(num_blocks);
> +				new = krealloc(edid, alloc_size, GFP_KERNEL);
> +				if (!new)
> +					goto fail;
> +				edid = new;
> +			}
>  		}
>  	}
>  
>  	if (invalid_blocks) {
> -		connector_bad_edid(connector, edid, edid_block_count(edid));
> +		connector_bad_edid(connector, edid, num_blocks);
>  
>  		edid = edid_filter_invalid_blocks(edid, &alloc_size);
>  	}
> @@ -3825,6 +3860,7 @@ static int add_detailed_modes(struct drm_connector *connector,
>  #define CTA_EXT_DB_HDR_STATIC_METADATA	6
>  #define CTA_EXT_DB_420_VIDEO_DATA	14
>  #define CTA_EXT_DB_420_VIDEO_CAP_MAP	15
> +#define CTA_EXT_DB_HF_EEODB		0x78
>  #define CTA_EXT_DB_HF_SCDB		0x79
>  
>  #define EDID_BASIC_AUDIO	(1 << 6)
> @@ -4884,6 +4920,12 @@ static bool cea_db_is_hdmi_forum_vsdb(const struct cea_db *db)
>  		cea_db_payload_len(db) >= 7;
>  }
>  
> +static bool cea_db_is_hdmi_forum_eeodb(const void *db)
> +{
> +	return cea_db_is_extended_tag(db, CTA_EXT_DB_HF_EEODB) &&
> +		cea_db_payload_len(db) >= 2;
> +}
> +
>  static bool cea_db_is_microsoft_vsdb(const struct cea_db *db)
>  {
>  	return cea_db_is_vendor(db, MICROSOFT_IEEE_OUI) &&
> @@ -4918,6 +4960,47 @@ static bool cea_db_is_hdmi_hdr_metadata_block(const struct cea_db *db)
>  		cea_db_payload_len(db) >= 3;
>  }
>  
> +/*
> + * Get the HF-EEODB override extension block count from EDID.
> + *
> + * The passed in EDID may be partially read, as long as it has at least two
> + * blocks (base block and one extension block) if EDID extension count is > 0.
> + *
> + * Note that this is *not* how you should parse CTA Data Blocks in general; this
> + * is only to handle partially read EDIDs. Normally, use the CTA Data Block
> + * iterators instead.
> + *
> + * References:
> + * - HDMI 2.1 section 10.3.6 HDMI Forum EDID Extension Override Data Block
> + */
> +static int edid_hfeeodb_extension_block_count(const struct edid *edid)
> +{
> +	const u8 *cta;
> +
> +	/* No extensions according to base block, no HF-EEODB. */
> +	if (!edid_extension_block_count(edid))
> +		return 0;
> +
> +	/* HF-EEODB is always in the first EDID extension block only */
> +	cta = edid_extension_block_data(edid, 0);
> +	if (edid_block_tag(cta) != CEA_EXT || cea_revision(cta) < 3)
> +		return 0;
> +
> +	/* Need to have the data block collection, and at least 3 bytes. */
> +	if (cea_db_collection_size(cta) < 3)
> +		return 0;
> +
> +	/*
> +	 * Sinks that include the HF-EEODB in their E-EDID shall include one and
> +	 * only one instance of the HF-EEODB in the E-EDID, occupying bytes 4
> +	 * through 6 of Block 1 of the E-EDID.
> +	 */
> +	if (!cea_db_is_hdmi_forum_eeodb(&cta[4]))
> +		return 0;
> +
> +	return cta[4 + 2];
> +}
> +
>  static void drm_parse_y420cmdb_bitmap(struct drm_connector *connector,
>  				      const u8 *db)
>  {
> -- 
> 2.30.2

-- 
Ville Syrjälä
Intel