ASoC: soc-cache: Warn on syncing any non-writable registers

When syncing the cache, if the driver has given us a writable_register()
callback, use it to check if we are syncing a non-writable register
and if so warn the user.
Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-cache.c

@@ -661,6 +661,8 @@ static int snd_soc_rbtree_cache_sync(struct snd_soc_codec *codec)
 		rbnode = rb_entry(node, struct snd_soc_rbtree_node, node);
 		if (rbnode->value == rbnode->defval)
 			continue;
+		WARN_ON(codec->writable_register &&
+			codec->writable_register(codec, rbnode->reg));
 		ret = snd_soc_cache_read(codec, rbnode->reg, &val);
 		if (ret)
 			return ret;
@@ -921,6 +923,8 @@ static int snd_soc_lzo_cache_sync(struct snd_soc_codec *codec)
 
 	lzo_blocks = codec->reg_cache;
 	for_each_set_bit(i, lzo_blocks[0]->sync_bmp, lzo_blocks[0]->sync_bmp_nbits) {
+		WARN_ON(codec->writable_register &&
+			codec->writable_register(codec, i));
 		ret = snd_soc_cache_read(codec, i, &val);
 		if (ret)
 			return ret;
@@ -1179,6 +1183,8 @@ static int snd_soc_flat_cache_sync(struct snd_soc_codec *codec)
 
 	codec_drv = codec->driver;
 	for (i = 0; i < codec_drv->reg_cache_size; ++i) {
+		WARN_ON(codec->writable_register &&
+			codec->writable_register(codec, i));
 		ret = snd_soc_cache_read(codec, i, &val);
 		if (ret)
 			return ret;