drm/edid: add function to help find SADs

Add a function to find the start of the SADs in the ELD. This
complements the helper to retrieve the SAD count.

Signed-off-by: Russell King <[e-mail]>

include/drm/drm_edid.h

···
 }
 
 /**
+ * drm_eld_sad - Get ELD SAD structures.
+ * @eld: pointer to an eld memory structure with sad_count set
+ */
+static inline const uint8_t *drm_eld_sad(const uint8_t *eld)
+{
+	unsigned int ver, mnl;
+
+	ver = (eld[DRM_ELD_VER] & DRM_ELD_VER_MASK) >> DRM_ELD_VER_SHIFT;
+	if (ver != 2 && ver != 31)
+		return NULL;
+
+	mnl = drm_eld_mnl(eld);
+	if (mnl > 16)
+		return NULL;
+
+	return eld + DRM_ELD_CEA_SAD(mnl, 0);
+}
+
+/**
  * drm_eld_sad_count - Get ELD SAD count.
  * @eld: pointer to an eld memory structure with sad_count set
  */