On 08/04/2016 04:55 PM, Cristian Birsan wrote: > Add a function to check if a regmap register is cached. This will be used > in debugfs to dump the cached values of write only registers. > > Signed-off-by: Cristian Birsan <[email protected]> > --- > drivers/base/regmap/internal.h | 1 + > drivers/base/regmap/regmap.c | 14 ++++++++++++++ > 2 files changed, 15 insertions(+) > > diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h > index 3df9770..cae04f4 100644 > --- a/drivers/base/regmap/internal.h > +++ b/drivers/base/regmap/internal.h > @@ -171,6 +171,7 @@ struct regcache_ops { > int (*drop)(struct regmap *map, unsigned int min, unsigned int max); > }; > > +bool regmap_cached(struct regmap *map, unsigned int reg); > bool regmap_writeable(struct regmap *map, unsigned int reg); > bool regmap_readable(struct regmap *map, unsigned int reg); > bool regmap_volatile(struct regmap *map, unsigned int reg); > diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c > index 4ac63c0..e07f3a9 100644 > --- a/drivers/base/regmap/regmap.c > +++ b/drivers/base/regmap/regmap.c > @@ -92,6 +92,20 @@ bool regmap_writeable(struct regmap *map, unsigned int reg) > return true; > } > > +bool regmap_cached(struct regmap *map, unsigned int reg) > +{ > + if (map->cache == REGCACHE_NONE) > + return false; > + > + if (!map->cache_ops) > + return false; > + > + if (map->max_register && reg > map->max_register) > + return false;
There is a problem with this approach. It does not check if the register is cached it only checks if the register is cacheable. This works very poorly for devices with sparse register maps. Sparse register maps do not assign a register to each register number. There are often even large gaps in the register map and some devices use up their full 16-bit register space. Now this change combined with the next patch will cause the register file to contain an entry for every possible register number, even if the register number is not assigned. Since unassigned registers are not cached regcache_read() will return an error and the registers file will print XX for the register value. This means for sparse register maps the registers file will be full of thousands of such entries.
