On 04/18/2016 01:32 PM, Mark Brown wrote: > On Sun, Apr 17, 2016 at 09:36:10AM +0100, Jonathan Cameron wrote: >> On 11/04/16 16:08, Crestez Dan Leonard wrote: >>> I used REGCACHE_FLAT because my device has a very small number of >>> registers and I assume it uses less memory. Honestly it would make >>> sense for regmap to include a REGCACHE_AUTO cache_type and pick the >>> cache implementation automatically based on number of registers. > >> I've fallen for that one in the past as well. AUTO would indeed >> be good if it was easy to do. > > It's extremely easy to do. Unless you've got a good reason to do > anything else you should always be using an rbtree. The core would > never select anything else. Ok, I will remember this. >>> Yes. It would not work otherwise since the regmap cache is explicitly >>> initialized with my listed defaults. >>> As far as I can tell regmap_write will always write to the hardware. > >> Interesting and counter intuitive if true... > > No, if the driver asked to write then we write. If the driver wants to > do a read/modify/write cycle it should use regmap_update_bits(). As a further clarification: regmap_write will write to hardware even if the cache is known to be up-to-date and no matter the regcache_type. Did I understand this correctly? I'm basing this on reading the code, it seems to me that map->reg_write is only avoided on error paths or if map->cache_only is set to true. This always-write guarantee is not obvious and if it's OK for drivers to rely on it perhaps it should be explicitly documented on regmap_write. Otherwise for my device I would need some way to mention that the device starts in an undefined state, not what is specified in reg_defaults. For simplicity I will drop regmap_config.reg_defaults completely and just setup the few parameters I need explicitly. This will be in v3. -- Regards, Leonard -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
