Re: [PATCH v2] drm/edid: rename macro for CEA extended-tag

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

On Mon, Jul 03, 2017 at 07:53:44PM +0530, Shashank Sharma wrote:
> CEA-861-F introduces extended tag codes for EDID extension blocks,
> which indicates the actual type of the data block. The code for
> using exteded tag is 0x7, whereas in the existing code, the
> corresponding macro is named as "VIDEO_CAPABILITY_BLOCK"
> 
> This patch renames the macro and usages from "VIDEO_CAPABILITY_BLOCK"
> to "CEA_EXTENDED_TAG"
> 
> V2: Add extended tag code check for video capabilitiy block (ville)
> 
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 2e55599..5bf9ffe 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -2566,7 +2566,8 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
>  #define VIDEO_BLOCK     0x02
>  #define VENDOR_BLOCK    0x03
>  #define SPEAKER_BLOCK	0x04
> -#define VIDEO_CAPABILITY_BLOCK	0x07
> +#define CEA_EXTENDED_TAG	0x07
> +#define VIDEO_CAPBLK_EXT_TAG	0x0

We don't have the _TAG suffix in the other defines either.
So maybe something like this?

...
#define SPEAKER_BLOCK        0x04
#define USE_EXTENDED_TAG     0x07
#define EXT_VIDEO_CAPABILITY_BLOCK	0x00

>  #define EDID_BASIC_AUDIO	(1 << 6)
>  #define EDID_CEA_YCRCB444	(1 << 5)
>  #define EDID_CEA_YCRCB422	(1 << 4)
> @@ -3218,6 +3219,12 @@ cea_db_payload_len(const u8 *db)
>  }
>  
>  static int
> +cea_db_extended_tag(const u8 *db)
> +{
> +	return db[1];
> +}
> +
> +static int
>  cea_db_tag(const u8 *db)
>  {
>  	return db[0] >> 5;
> @@ -3793,7 +3800,9 @@ bool drm_rgb_quant_range_selectable(struct edid *edid)
>  		return false;
>  
>  	for_each_cea_db(edid_ext, i, start, end) {
> -		if (cea_db_tag(&edid_ext[i]) == VIDEO_CAPABILITY_BLOCK &&
> +		if (cea_db_tag(&edid_ext[i]) == CEA_EXTENDED_TAG &&
> +		    cea_db_extended_tag(&edid_ext[i]) ==
> +			VIDEO_CAPBLK_EXT_TAG &&
>  		    cea_db_payload_len(&edid_ext[i]) == 2) {

And I suggest doing the length check before the ext tag check, otherwise
we're potentially accessing data outside the block. Well, as long as
there's *something* there the current order will work, but IMO it's
better to be a little paranoid when parsing stuff.

>  			DRM_DEBUG_KMS("CEA VCDB 0x%02x\n", edid_ext[i + 2]);
>  			return edid_ext[i + 2] & EDID_CEA_VCDB_QS;
> -- 
> 2.7.4

-- 
Ville Syrjälä
Intel OTC
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