Add helpers for Latency_Fields_Present and I_Latency_Fields_Present
bits, and fix the parsing:

- Respect specification regarding "I_Latency_Fields_Present shall be
  zero if Latency_Fields_Present is zero".

- Don't claim latency fields are present if the data block isn't big
  enough to hold them.

Cc: Ville Syrjälä <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
---
 drivers/gpu/drm/drm_edid.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 076ba125c38d..847076b29594 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4685,6 +4685,16 @@ static int add_3d_struct_modes(struct drm_connector 
*connector, u16 structure,
        return modes;
 }
 
+static bool hdmi_vsdb_latency_present(const u8 *db)
+{
+       return db[8] & BIT(7);
+}
+
+static bool hdmi_vsdb_i_latency_present(const u8 *db)
+{
+       return hdmi_vsdb_latency_present(db) && db[8] & BIT(6);
+}
+
 /*
  * do_hdmi_vsdb_modes - Parse the HDMI Vendor Specific data block
  * @connector: connector corresponding to the HDMI sink
@@ -5357,6 +5367,7 @@ drm_parse_hdr_metadata_block(struct drm_connector 
*connector, const u8 *db)
        }
 }
 
+/* HDMI Vendor-Specific Data Block (HDMI VSDB, H14b-VSDB) */
 static void
 drm_parse_hdmi_vsdb_audio(struct drm_connector *connector, const u8 *db)
 {
@@ -5364,18 +5375,18 @@ drm_parse_hdmi_vsdb_audio(struct drm_connector 
*connector, const u8 *db)
 
        if (len >= 6 && (db[6] & (1 << 7)))
                connector->eld[DRM_ELD_SAD_COUNT_CONN_TYPE] |= 
DRM_ELD_SUPPORTS_AI;
-       if (len >= 8) {
-               connector->latency_present[0] = db[8] >> 7;
-               connector->latency_present[1] = (db[8] >> 6) & 1;
-       }
-       if (len >= 9)
+
+       if (len >= 10 && hdmi_vsdb_latency_present(db)) {
+               connector->latency_present[0] = true;
                connector->video_latency[0] = db[9];
-       if (len >= 10)
                connector->audio_latency[0] = db[10];
-       if (len >= 11)
+       }
+
+       if (len >= 12 && hdmi_vsdb_i_latency_present(db)) {
+               connector->latency_present[1] = true;
                connector->video_latency[1] = db[11];
-       if (len >= 12)
                connector->audio_latency[1] = db[12];
+       }
 
        drm_dbg_kms(connector->dev,
                    "[CONNECTOR:%d:%s] HDMI: latency present %d %d, video 
latency %d %d, audio latency %d %d\n",
-- 
2.34.1

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