regmap: Allow drivers to reinitialise the register cache at runtime

Sometimes the register map information may change in ways that drivers can
discover at runtime. For example, new revisions of a device may add new
registers. Support runtime discovery by drivers by allowing the register
cache to be reinitialised with a new function regmap_reinit_cache() which
discards the existing cache and creates a new one.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regmap.c

@@ -230,6 +230,39 @@ struct regmap *regmap_init(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(regmap_init);
 
+/**
+ * regmap_reinit_cache(): Reinitialise the current register cache
+ *
+ * @map: Register map to operate on.
+ * @config: New configuration.  Only the cache data will be used.
+ *
+ * Discard any existing register cache for the map and initialize a
+ * new cache.  This can be used to restore the cache to defaults or to
+ * update the cache configuration to reflect runtime discovery of the
+ * hardware.
+ */
+int regmap_reinit_cache(struct regmap *map, const struct regmap_config *config)
+{
+	int ret;
+
+	mutex_lock(&map->lock);
+
+	regcache_exit(map);
+
+	map->max_register = config->max_register;
+	map->writeable_reg = config->writeable_reg;
+	map->readable_reg = config->readable_reg;
+	map->volatile_reg = config->volatile_reg;
+	map->precious_reg = config->precious_reg;
+	map->cache_type = config->cache_type;
+
+	ret = regcache_init(map, config);
+
+	mutex_unlock(&map->lock);
+
+	return ret;
+}
+
 /**
  * regmap_exit(): Free a previously allocated register map
  */

include/linux/regmap.h

@@ -129,6 +129,8 @@ struct regmap *regmap_init_spi(struct spi_device *dev,
 			       const struct regmap_config *config);
 
 void regmap_exit(struct regmap *map);
+int regmap_reinit_cache(struct regmap *map,
+			const struct regmap_config *config);
 int regmap_write(struct regmap *map, unsigned int reg, unsigned int val);
 int regmap_raw_write(struct regmap *map, unsigned int reg,
 		     const void *val, size_t val_len);