[v9 03/13] drm: Parse HDR metadata info from EDID

[Shankar, Uma]

>-----Original Message-----
>From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>Sent: Tuesday, May 14, 2019 12:49 AM
>To: Shankar, Uma <uma.shankar at intel.com>
>Cc: intel-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org;
>dcastagna at chromium.org; jonas at kwiboo.se; emil.l.velikov at gmail.com;
>seanpaul at chromium.org; Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
><maarten.lankhorst at intel.com>
>Subject: Re: [v9 03/13] drm: Parse HDR metadata info from EDID
>
>On Thu, May 09, 2019 at 12:08:43AM +0530, Uma Shankar wrote:
>> HDR metadata block is introduced in CEA-861.3 spec.
>> Parsing the same to get the panel's HDR metadata.
>>
>> v2: Rebase and added Ville's POC changes to the patch.
>>
>> v3: No Change
>>
>> v4: Addressed Shashank's review comments
>>
>> v5: Addressed Shashank's comment and added his RB.
>>
>> v6: Addressed Jonas Karlman review comments.
>>
>> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>> Reviewed-by: Shashank Sharma <shashank.sharma at intel.com>
>> ---
>>  drivers/gpu/drm/drm_edid.c | 52
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 52 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
>> index 852bdd8..fe2c29b 100644
>> --- a/drivers/gpu/drm/drm_edid.c
>> +++ b/drivers/gpu/drm/drm_edid.c
>> @@ -2852,6 +2852,7 @@ static int drm_cvt_modes(struct drm_connector
>*connector,
>>  #define VIDEO_BLOCK     0x02
>>  #define VENDOR_BLOCK    0x03
>>  #define SPEAKER_BLOCK	0x04
>> +#define HDR_STATIC_METADATA_BLOCK	0x6
>>  #define USE_EXTENDED_TAG 0x07
>>  #define EXT_VIDEO_CAPABILITY_BLOCK 0x00
>>  #define EXT_VIDEO_DATA_BLOCK_420	0x0E
>> @@ -3599,6 +3600,12 @@ static int add_3d_struct_modes(struct
>> drm_connector *connector, u16 structure,  }
>>
>>  static int
>> +cea_db_payload_len_ext(const u8 *db)
>> +{
>> +	return (db[0] & 0x1f) - 1;
>> +}
>> +
>> +static int
>>  cea_db_extended_tag(const u8 *db)
>>  {
>>  	return db[1];
>> @@ -3834,6 +3841,49 @@ static void fixup_detailed_cea_mode_clock(struct
>drm_display_mode *mode)
>>  	mode->clock = clock;
>>  }
>>
>> +static bool cea_db_is_hdmi_hdr_metadata_block(const u8 *db) {
>> +	if (cea_db_tag(db) != USE_EXTENDED_TAG)
>> +		return false;
>> +
>> +	if (db[1] != HDR_STATIC_METADATA_BLOCK)
>> +		return false;
>> +
>> +	return true;
>> +}
>> +
>> +static uint8_t eotf_supported(const u8 *edid_ext) {
>> +	return edid_ext[2] &
>> +		(BIT(HDMI_EOTF_TRADITIONAL_GAMMA_SDR) |
>> +		 BIT(HDMI_EOTF_TRADITIONAL_GAMMA_HDR) |
>> +		 BIT(HDMI_EOTF_SMPTE_ST2084));
>> +}
>> +
>> +static uint8_t hdr_metadata_type(const u8 *edid_ext) {
>> +	return edid_ext[3] &
>> +		BIT(HDMI_STATIC_METADATA_TYPE1);
>> +}
>> +
>> +static void
>> +drm_parse_hdr_metadata_block(struct drm_connector *connector, const
>> +u8 *db) {
>> +	u16 len;
>> +
>> +	len = cea_db_payload_len_ext(db);
>> +	connector->hdr_sink_metadata.hdmi_type1.eotf = eotf_supported(db);
>> +	connector->hdr_sink_metadata.hdmi_type1.metadata_type =
>> +					hdr_metadata_type(db);
>
>Length checks missing for this stuff.

The above 2 are mandatory bytes , so this will always be there in this block.
Byte 5 to 7 are optional and depends on length field. So we should not need a length
check here for above 2 fields. Hope my understanding is right.

>> +
>> +	if (len >= 4)
>> +		connector->hdr_sink_metadata.hdmi_type1.max_cll = db[4];
>> +	if (len >= 5)
>> +		connector->hdr_sink_metadata.hdmi_type1.max_fall = db[5];
>> +	if (len >= 6)
>> +		connector->hdr_sink_metadata.hdmi_type1.min_cll = db[6];
>
>All the length checks seem to be off by one due to cea_db_payload_len_ext().
>I think just dropping cea_db_payload_len_ext() would make things better since a)
>nothing else has that, b) db still points at the start of the whole data block instead of
>the payload.

 The length field adds/includes the extended tag byte while reporting the size of block. So we need to
remove 1 byte to get the correct size of data. A value of n = 3 means bytes 5 to 7 are not present.

>The while payload vs. block length thing is already confusing anyway.
>I have a feeling we should replace cea_db_payload_len() with something that returns
>the length of the whole data block. That way the db[index] vs. length checks would
>start to make some sense to the casual reader.

I hope with above understanding, in db[index], index just tells the byte number for a particular
field which matches exactly to spec offsets.

Regards,
Uma Shankar

>
>> +}
>> +
>>  static void
>>  drm_parse_hdmi_vsdb_audio(struct drm_connector *connector, const u8
>> *db)  { @@ -4461,6 +4511,8 @@ static void drm_parse_cea_ext(struct
>> drm_connector *connector,
>>  			drm_parse_y420cmdb_bitmap(connector, db);
>>  		if (cea_db_is_vcdb(db))
>>  			drm_parse_vcdb(connector, db);
>> +		if (cea_db_is_hdmi_hdr_metadata_block(db))
>> +			drm_parse_hdr_metadata_block(connector, db);
>>  	}
>>  }
>>
>> --
>> 1.9.1
>>
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>> dri-devel at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>--
>Ville Syrjälä
>Intel