Linux Device Drivers Development

regmap and cache

Obviously, regmap supports caching. Whether the cache system is used or not depends on the value of the cache_type field in regmap_config. Looking at include/linux/regmap.h, accepted values are:

/* Anenum of all the supported cache types */ 
enum regcache_type { 
   REGCACHE_NONE, 
   REGCACHE_RBTREE, 
   REGCACHE_COMPRESSED, 
   REGCACHE_FLAT, 
}; 

It is set to REGCACHE_NONE by default, meaning that the cache is disabled. Other values simply define how the cache should be stored.

Your device may have a predefined power-on-reset value in certain registers. Those values can be stored in an array, so that any read operation returns the value contained in the array. However, any write operation affects the real register in the device and updates ...