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@xxxxxxxxxxxxxxx>
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> 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
