[RFC 16/19] drm/edid: detect basic audio only on CEA extension

[Jani Nikula]

The CTA data block in DisplayID does not have the bits from byte 3 that
a CEA extension has. Only look for them in CEA extensions, but also look
for them in all CEA extensions.

References: https://patchwork.freedesktop.org/patch/msgid/20220321044330.27723-1-cooper.chiou@intel.com
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/drm_edid.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index b3aedeefed82..b6675f8638bb 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4959,16 +4959,21 @@ EXPORT_SYMBOL(drm_detect_hdmi_monitor);
  */
 bool drm_detect_monitor_audio(struct edid *edid)
 {
+	struct drm_edid_iter edid_iter;
 	const struct cea_db *db;
 	struct cea_db_iter iter;
-	const u8 *edid_ext;
+	const u8 *cea;
 	bool has_audio = false;
 
-	edid_ext = drm_find_cea_extension(edid);
-	if (!edid_ext)
-		goto end;
-
-	has_audio = ((edid_ext[3] & EDID_BASIC_AUDIO) != 0);
+	drm_edid_iter_begin(edid, &edid_iter);
+	drm_edid_iter_for_each(cea, &edid_iter) {
+		if (cea[0] == CEA_EXT) {
+			has_audio = cea[3] & EDID_BASIC_AUDIO;
+			if (has_audio)
+				break;
+		}
+	}
+	drm_edid_iter_end(&edid_iter);
 
 	if (has_audio) {
 		DRM_DEBUG_KMS("Monitor has basic audio support\n");
-- 
2.30.2