Re: [PATCH v8 2/8] mfd: simple-mfd-i2c: specify max_register

Lee Jones
2025-07-23T09:51:32Z

On Thu, 10 Jul 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 custom configuration, but no existing device uses it.
>
> Rather than specify a "full" regmap configuration to change only
> the max_register value, Lee Jones suggested allowing max_register
> to be specified in the simple_mfd_data structure. If regmap_config
> and max_register are both supplied, the max_register field is ignored.
>
> Signed-off-by: Alex Elder <elder@riscstar.com>
> Suggested-by: Lee Jones <lee@kernel.org>
> ---
> v8: - Use regmap_config_8r_8v, modifying it if max_register supplied
>
> drivers/mfd/simple-mfd-i2c.c | 8 ++++++--
> drivers/mfd/simple-mfd-i2c.h | 3 ++-
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
> index 22159913bea03..5138aa72140b5 100644
> --- a/drivers/mfd/simple-mfd-i2c.c
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -24,15 +24,16 @@
>
> #include "simple-mfd-i2c.h"
>
> -static const struct regmap_config regmap_config_8r_8v = {
> +static struct regmap_config regmap_config_8r_8v = {
> .reg_bits = 8,
> .val_bits = 8,
> + /* .max_register can be specified in simple_mfd_data */

Drop this comment please.

> };
>
> 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;
>
> @@ -43,8 +44,11 @@ static int simple_mfd_i2c_probe(struct i2c_client *i2c)
> regmap_config = &regmap_config_8r_8v;
> else
> regmap_config = simple_mfd_data->regmap_config;
> + if (simple_mfd_data && !simple_mfd_data->regmap_config)
> + regmap_config->max_register = simple_mfd_data->max_register;

If max_register is set in simple_mfd_data, it should take precedence.

if (simple_mfd_data && simple_mfd_data->max_register)
regmap_config->max_register = simple_mfd_data->max_register;

> regmap = devm_regmap_init_i2c(i2c, regmap_config);
> + regmap_config->max_register = 0;

Does max_register definitely have persistence over subsequent calls?

> 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..ea2a96af8bce4 100644
> --- a/drivers/mfd/simple-mfd-i2c.h
> +++ b/drivers/mfd/simple-mfd-i2c.h
> @@ -24,7 +24,8 @@
> #include <linux/regmap.h>
>
> struct simple_mfd_data {
> - const struct regmap_config *regmap_config;
> + struct regmap_config *regmap_config;
> + unsigned int max_register; /* Ignored if regmap_config supplied */
> const struct mfd_cell *mfd_cell;
> size_t mfd_cell_size;
> };
> --
> 2.45.2
>

--
Lee Jones [李琼斯]