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This causes > false positives on hardware where many registers reset to zero but are > not listed in reg_defaults, forcing drivers to maintain large tables > just to silence the warning. > > Add a reg_default_cb() hook so drivers can supply defaults for registers > not present in reg_defaults when populating REGCACHE_FLAT. This keeps > the warning quiet for known zero-reset registers without bloating > tables. Provide a generic regmap_default_zero_cb() helper for drivers > that need zero defaults. > > The hook is only used for REGCACHE_FLAT; the core does not > check readable/writeable access, so drivers must provide readable_reg/ > writeable_reg callbacks and handle holes in the register map. > > Signed-off-by: Sheetal > --- > drivers/base/regmap/internal.h | 3 +++ > drivers/base/regmap/regcache-flat.c | 19 +++++++++++++++++++ > drivers/base/regmap/regcache.c | 3 ++- > drivers/base/regmap/regmap.c | 2 ++ > include/linux/regmap.h | 14 ++++++++++++++ > 5 files changed, 40 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h > index 1477329410ec..5bf993165438 100644 > --- a/drivers/base/regmap/internal.h > +++ b/drivers/base/regmap/internal.h > @@ -117,6 +117,9 @@ struct regmap { > void *val_buf, size_t val_size); > int (*write)(void *context, const void *data, size_t count); > > + int (*reg_default_cb)(struct device *dev, unsigned int reg, > + unsigned int *val); > + > unsigned long read_flag_mask; > unsigned long write_flag_mask; > > diff --git a/drivers/base/regmap/regcache-flat.c b/drivers/base/regmap/regcache-flat.c > index 53cc59c84e2f..c924817e19b1 100644 > --- a/drivers/base/regmap/regcache-flat.c > +++ b/drivers/base/regmap/regcache-flat.c > @@ -79,6 +79,25 @@ static int regcache_flat_populate(struct regmap *map) > __set_bit(index, cache->valid); > } > > + if (map->reg_default_cb) { > + dev_dbg(map->dev, > + "Populating regcache_flat using reg_default_cb callback\n"); > + > + for (i = 0; i <= map->max_register; i += map->reg_stride) { > + unsigned int index = regcache_flat_get_index(map, i); > + unsigned int value; > + > + if (test_bit(index, cache->valid)) > + continue; > + > + if (map->reg_default_cb(map->dev, i, &value)) > + continue; > + > + cache->data[index] = value; > + __set_bit(index, cache->valid); > + } > + } > + > return 0; > } > > diff --git a/drivers/base/regmap/regcache.c b/drivers/base/regmap/regcache.c > index 319c342bf5a0..31bdbf37dbed 100644 > --- a/drivers/base/regmap/regcache.c > +++ b/drivers/base/regmap/regcache.c > @@ -223,7 +223,8 @@ int regcache_init(struct regmap *map, const struct regmap_config *config) > goto err_free; > } > > - if (map->num_reg_defaults && map->cache_ops->populate) { > + if (map->cache_ops->populate && > + (map->num_reg_defaults || map->reg_default_cb)) { > dev_dbg(map->dev, "Populating %s cache\n", map->cache_ops->name); > map->lock(map->lock_arg); > ret = map->cache_ops->populate(map); > diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c > index ce9be3989a21..57c5551044ed 100644 > --- a/drivers/base/regmap/regmap.c > +++ b/drivers/base/regmap/regmap.c > @@ -811,6 +811,7 @@ struct regmap *__regmap_init(struct device *dev, > map->precious_reg = config->precious_reg; > map->writeable_noinc_reg = config->writeable_noinc_reg; > map->readable_noinc_reg = config->readable_noinc_reg; > + map->reg_default_cb = config->reg_default_cb; > map->cache_type = config->cache_type; > > spin_lock_init(&map->async_lock); > @@ -1433,6 +1434,7 @@ int regmap_reinit_cache(struct regmap *map, const struct regmap_config *config) > map->precious_reg = config->precious_reg; > map->writeable_noinc_reg = config->writeable_noinc_reg; > map->readable_noinc_reg = config->readable_noinc_reg; > + map->reg_default_cb = config->reg_default_cb; > map->cache_type = config->cache_type; > > ret = regmap_set_name(map, config); > diff --git a/include/linux/regmap.h b/include/linux/regmap.h > index b0b9be750d93..51940eeff872 100644 > --- a/include/linux/regmap.h > +++ b/include/linux/regmap.h > @@ -359,6 +359,10 @@ typedef void (*regmap_unlock)(void *); > * @reg_defaults: Power on reset values for registers (for use with > * register cache support). > * @num_reg_defaults: Number of elements in reg_defaults. > + * @reg_default_cb: Optional callback to return default values for registers > + * not listed in reg_defaults. This is only used for > + * REGCACHE_FLAT population; drivers must ensure the readable_reg/ > + * writeable_reg callbacks are defined to handle holes. > * > * @read_flag_mask: Mask to be set in the top bytes of the register when doing > * a read. > @@ -449,6 +453,8 @@ struct regmap_config { > const struct regmap_access_table *rd_noinc_table; > const struct reg_default *reg_defaults; > unsigned int num_reg_defaults; > + int (*reg_default_cb)(struct device *dev, unsigned int reg, > + unsigned int *def); > enum regcache_type cache_type; > const void *reg_defaults_raw; > unsigned int num_reg_defaults_raw; > @@ -1349,6 +1355,14 @@ static inline int regmap_write_bits(struct regmap *map, unsigned int reg, > return regmap_update_bits_base(map, reg, mask, val, NULL, false, true); > } > > +static inline int regmap_default_zero_cb(struct device *dev, > + unsigned int reg, > + unsigned int *def) > +{ > + *def = 0; > + return 0; It might be worth ... if (!def) return -EINVAL; *def = 0; Otherwise ... Reviewed-by: Jon Hunter Tested-by: Jon Hunter Thanks Jon -- nvpublic