[PATCH v7 10/22] drm/edid: add helper for HDMI VSDB audio latency field length

[Ville Syrjälä]

On Wed, Jan 04, 2023 at 12:05:25PM +0200, Jani Nikula wrote:
> Add a helper for skipping the HDMI VSDB audio latency fields.
> 
> There's a functional change for HDMI VSDB blocks that do not respect the
> spec: "I_Latency_Fields_Present shall be zero if Latency_Fields_Present
> is zero". We assume this to hold when skipping the latency fields, and
> ignore non-zero I_Latency_Fields_Present if Latency_Fields_Present is
> zero.
> 
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

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

> ---
>  drivers/gpu/drm/drm_edid.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 847076b29594..93067b8dd9f6 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4695,6 +4695,16 @@ static bool hdmi_vsdb_i_latency_present(const u8 *db)
>  	return hdmi_vsdb_latency_present(db) && db[8] & BIT(6);
>  }
>  
> +static int hdmi_vsdb_latency_length(const u8 *db)
> +{
> +	if (hdmi_vsdb_i_latency_present(db))
> +		return 4;
> +	else if (hdmi_vsdb_latency_present(db))
> +		return 2;
> +	else
> +		return 0;
> +}
> +
>  /*
>   * do_hdmi_vsdb_modes - Parse the HDMI Vendor Specific data block
>   * @connector: connector corresponding to the HDMI sink
> @@ -4720,13 +4730,7 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len)
>  	if (!(db[8] & (1 << 5)))
>  		goto out;
>  
> -	/* Latency_Fields_Present */
> -	if (db[8] & (1 << 7))
> -		offset += 2;
> -
> -	/* I_Latency_Fields_Present */
> -	if (db[8] & (1 << 6))
> -		offset += 2;
> +	offset += hdmi_vsdb_latency_length(db);
>  
>  	/* the declared length is not long enough for the 2 first bytes
>  	 * of additional video format capabilities */
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel