Re: [PATCH v6 2/8] mfd: simple-mfd-i2c: specify max_register

Lee Jones
2025-07-02T15:26:25Z

On Fri, 27 Jun 2025, Alex Elder wrote:

> All devices supported by simple MFD use the same 8-bit register
> 8-bit value regmap configuration. There is an option available
> for a device to specify a custome configuration, but no existing
> device uses it.
>
> Lee Jones suggested modifying the simple MFD implementation to
> remove the generality of the full regmap configuration and add a
> max_register value to the simple_mfd_data structure. This can
> be used in the regmap configuration to limit the valid register
> addresses if desired. It's simpler, and covers all existing and
> anticipated device types.

Woah, not like this. I wanted to make the framework _more_ flexible.

Just this should do what you want:

diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
index 22159913bea0..f43be10c0e60 100644
--- a/drivers/mfd/simple-mfd-i2c.c
+++ b/drivers/mfd/simple-mfd-i2c.c
@@ -44,6 +44,9 @@ static int simple_mfd_i2c_probe(struct i2c_client *i2c)
else
regmap_config = simple_mfd_data->regmap_config;

+ if (simple_mfd_data->max_register)
+ regmap_config->max_register = simple_mfd_data->max_register;
+
regmap = devm_regmap_init_i2c(i2c, regmap_config);
if (IS_ERR(regmap))
return PTR_ERR(regmap);

Plus the one line change in drivers/mfd/simple-mfd-i2c.h.

> Signed-off-by: Alex Elder <elder@riscstar.com>
> Suggested-by: Lee Jones <lee@kernel.org>
> ---
> v6: - New patch, changing the simple MFD functionality
>
> drivers/mfd/simple-mfd-i2c.c | 18 ++++++------------
> drivers/mfd/simple-mfd-i2c.h | 2 +-
> 2 files changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
> index 22159913bea03..c1dc315d44dcf 100644
> --- a/drivers/mfd/simple-mfd-i2c.c
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -24,27 +24,21 @@
>
> #include "simple-mfd-i2c.h"
>
> -static const struct regmap_config regmap_config_8r_8v = {
> - .reg_bits = 8,
> - .val_bits = 8,
> -};
> -
> static int simple_mfd_i2c_probe(struct i2c_client *i2c)
> {
> const struct simple_mfd_data *simple_mfd_data;
> - const struct regmap_config *regmap_config;
> + struct regmap_config regmap_config = { };
> struct regmap *regmap;
> int ret;
>
> simple_mfd_data = device_get_match_data(&i2c->dev);
>
> - /* If no regmap_config is specified, use the default 8reg and 8val bits */
> - if (!simple_mfd_data || !simple_mfd_data->regmap_config)
> - regmap_config = &regmap_config_8r_8v;
> - else
> - regmap_config = simple_mfd_data->regmap_config;
> + regmap_config.reg_bits = 8;
> + regmap_config.val_bits = 8;
> + if (simple_mfd_data)
> + regmap_config.max_register = simple_mfd_data->max_register;
>
> - regmap = devm_regmap_init_i2c(i2c, regmap_config);
> + regmap = devm_regmap_init_i2c(i2c, &regmap_config);
> if (IS_ERR(regmap))
> return PTR_ERR(regmap);
>
> diff --git a/drivers/mfd/simple-mfd-i2c.h b/drivers/mfd/simple-mfd-i2c.h
> index 7cb2bdd347d97..4121fe1bc1d70 100644
> --- a/drivers/mfd/simple-mfd-i2c.h
> +++ b/drivers/mfd/simple-mfd-i2c.h
> @@ -24,9 +24,9 @@
> #include <linux/regmap.h>
>
> struct simple_mfd_data {
> - const struct regmap_config *regmap_config;
> const struct mfd_cell *mfd_cell;
> size_t mfd_cell_size;
> + unsigned int max_register;
> };
>
> #endif /* __MFD_SIMPLE_MFD_I2C_H */
> --
> 2.45.2
>

--
Lee Jones [李琼斯]