drm/edid: make a number of functions, parameters and variables const

If there's no need to change it, it should be const. There's more to be
done, but start off with changes that make follow-up work easier. No
functional changes.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/41722f92ef81cd6adf65f936fcc5301418e1f94b.1617024940.git.jani.nikula@intel.com

drivers/gpu/drm/drm_edid.c

@@ -1585,7 +1585,7 @@ module_param_named(edid_fixup, edid_fixup, int, 0400);
 MODULE_PARM_DESC(edid_fixup,
 		 "Minimum number of valid EDID header bytes (0-8, default 6)");
 
-static int validate_displayid(u8 *displayid, int length, int idx);
+static int validate_displayid(const u8 *displayid, int length, int idx);
 
 static int drm_edid_block_checksum(const u8 *raw_edid)
 {
@@ -3241,10 +3241,10 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 /*
  * Search EDID for CEA extension block.
  */
-static u8 *drm_find_edid_extension(const struct edid *edid,
+static const u8 *drm_find_edid_extension(const struct edid *edid,
 					 int ext_id, int *ext_index)
 {
-	u8 *edid_ext = NULL;
+	const u8 *edid_ext = NULL;
 	int i;
 
 	/* No EDID or EDID extensions */
@@ -3253,7 +3253,7 @@ static u8 *drm_find_edid_extension(const struct edid *edid,
 
 	/* Find CEA extension */
 	for (i = *ext_index; i < edid->extensions; i++) {
-		edid_ext = (u8 *)edid + EDID_LENGTH * (i + 1);
+		edid_ext = (const u8 *)edid + EDID_LENGTH * (i + 1);
 		if (edid_ext[0] == ext_id)
 			break;
 	}
@@ -3267,12 +3267,12 @@ static u8 *drm_find_edid_extension(const struct edid *edid,
 }
 
 
-static u8 *drm_find_displayid_extension(const struct edid *edid,
+static const u8 *drm_find_displayid_extension(const struct edid *edid,
 					      int *length, int *idx,
 					      int *ext_index)
 {
-	u8 *displayid = drm_find_edid_extension(edid, DISPLAYID_EXT, ext_index);
-	struct displayid_hdr *base;
+	const u8 *displayid = drm_find_edid_extension(edid, DISPLAYID_EXT, ext_index);
+	const struct displayid_hdr *base;
 	int ret;
 
 	if (!displayid)
@@ -3286,18 +3286,18 @@ static u8 *drm_find_displayid_extension(const struct edid *edid,
 	if (ret)
 		return NULL;
 
-	base = (struct displayid_hdr *)&displayid[*idx];
+	base = (const struct displayid_hdr *)&displayid[*idx];
 	*length = *idx + sizeof(*base) + base->bytes;
 
 	return displayid;
 }
 
-static u8 *drm_find_cea_extension(const struct edid *edid)
+static const u8 *drm_find_cea_extension(const struct edid *edid)
 {
 	int length, idx;
-	struct displayid_block *block;
-	u8 *cea;
-	u8 *displayid;
+	const struct displayid_block *block;
+	const u8 *cea;
+	const u8 *displayid;
 	int ext_index;
 
 	/* Look for a top level CEA extension block */
@@ -3318,7 +3318,7 @@ static u8 *drm_find_cea_extension(const struct edid *edid)
 		idx += sizeof(struct displayid_hdr);
 		for_each_displayid_db(displayid, block, idx, length) {
 			if (block->tag == DATA_BLOCK_CTA)
-				return (u8 *)block;
+				return (const u8 *)block;
 		}
 	}
 
@@ -4503,8 +4503,8 @@ static void clear_eld(struct drm_connector *connector)
 static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
 {
 	uint8_t *eld = connector->eld;
-	u8 *cea;
-	u8 *db;
+	const u8 *cea;
+	const u8 *db;
 	int total_sad_count = 0;
 	int mnl;
 	int dbl;
@@ -4600,7 +4600,7 @@ int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads)
 {
 	int count = 0;
 	int i, start, end, dbl;
-	u8 *cea;
+	const u8 *cea;
 
 	cea = drm_find_cea_extension(edid);
 	if (!cea) {
@@ -4619,7 +4619,7 @@ int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads)
 	}
 
 	for_each_cea_db(cea, i, start, end) {
-		u8 *db = &cea[i];
+		const u8 *db = &cea[i];
 
 		if (cea_db_tag(db) == AUDIO_BLOCK) {
 			int j;
@@ -4631,7 +4631,7 @@ int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads)
 			if (!*sads)
 				return -ENOMEM;
 			for (j = 0; j < count; j++) {
-				u8 *sad = &db[1 + j * 3];
+				const u8 *sad = &db[1 + j * 3];
 
 				(*sads)[j].format = (sad[0] & 0x78) >> 3;
 				(*sads)[j].channels = sad[0] & 0x7;
@@ -4755,7 +4755,7 @@ EXPORT_SYMBOL(drm_av_sync_delay);
  */
 bool drm_detect_hdmi_monitor(struct edid *edid)
 {
-	u8 *edid_ext;
+	const u8 *edid_ext;
 	int i;
 	int start_offset, end_offset;
 
@@ -4793,7 +4793,7 @@ EXPORT_SYMBOL(drm_detect_hdmi_monitor);
  */
 bool drm_detect_monitor_audio(struct edid *edid)
 {
-	u8 *edid_ext;
+	const u8 *edid_ext;
 	int i, j;
 	bool has_audio = false;
 	int start_offset, end_offset;
@@ -5287,13 +5287,13 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
 	return quirks;
 }
 
-static int validate_displayid(u8 *displayid, int length, int idx)
+static int validate_displayid(const u8 *displayid, int length, int idx)
 {
 	int i, dispid_length;
 	u8 csum = 0;
-	struct displayid_hdr *base;
+	const struct displayid_hdr *base;
 
-	base = (struct displayid_hdr *)&displayid[idx];
+	base = (const struct displayid_hdr *)&displayid[idx];
 
 	DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n",
 		      base->rev, base->bytes, base->prod_id, base->ext_count);
@@ -5359,7 +5359,7 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
 }
 
 static int add_displayid_detailed_1_modes(struct drm_connector *connector,
-					  struct displayid_block *block)
+					  const struct displayid_block *block)
 {
 	struct displayid_detailed_timing_block *det = (struct displayid_detailed_timing_block *)block;
 	int i;
@@ -5387,9 +5387,9 @@ static int add_displayid_detailed_1_modes(struct drm_connector *connector,
 static int add_displayid_detailed_modes(struct drm_connector *connector,
 					struct edid *edid)
 {
-	u8 *displayid;
+	const u8 *displayid;
 	int length, idx;
-	struct displayid_block *block;
+	const struct displayid_block *block;
 	int num_modes = 0;
 	int ext_index = 0;
 

include/drm/drm_displayid.h

@@ -93,11 +93,11 @@ struct displayid_detailed_timing_block {
 };
 
 #define for_each_displayid_db(displayid, block, idx, length) \
-	for ((block) = (struct displayid_block *)&(displayid)[idx]; \
+	for ((block) = (const struct displayid_block *)&(displayid)[idx]; \
 	     (idx) + sizeof(struct displayid_block) <= (length) && \
 	     (idx) + sizeof(struct displayid_block) + (block)->num_bytes <= (length) && \
 	     (block)->num_bytes > 0; \
 	     (idx) += sizeof(struct displayid_block) + (block)->num_bytes, \
-	     (block) = (struct displayid_block *)&(displayid)[idx])
+	     (block) = (const struct displayid_block *)&(displayid)[idx])
 
 #endif