drm/edid: abstract cea data block collection size

Add a function to get the cea data block collection size.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/5339ab3249400a3c41001967e7ff2611b58e0425.1654674560.git.jani.nikula@intel.com

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index c57f6333ea7d74a2b592336a11b2e5eef3b62216..002816509fc8447a88ef4d517335a47642420b8c 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4482,6 +4482,20 @@ __cea_db_iter_current_block(const struct cea_db_iter *iter)
        return NULL;
 }
 
+/*
+ * References:
+ * - CTA-861-H section 7.3.3 CTA Extension Version 3
+ */
+static int cea_db_collection_size(const u8 *cta)
+{
+       u8 d = cta[2];
+
+       if (d < 4 || d > 127)
+               return 0;
+
+       return d - 4;
+}
+
 /*
  * References:
  * - VESA E-EDID v1.4
@@ -4492,15 +4506,19 @@ static const void *__cea_db_iter_edid_next(struct cea_db_iter *iter)
        const u8 *ext;
 
        drm_edid_iter_for_each(ext, &iter->edid_iter) {
+               int size;
+
                /* Only support CTA Extension revision 3+ */
                if (ext[0] != CEA_EXT || cea_revision(ext) < 3)
                        continue;
 
-               iter->index = 4;
-               iter->end = ext[2];
-               if (iter->end < 4 || iter->end > 127)
+               size = cea_db_collection_size(ext);
+               if (!size)
                        continue;
 
+               iter->index = 4;
+               iter->end = iter->index + size;
+
                return ext;
        }