linux-kernel - Re: [PATCH v6 2/8] mfd: simple-mfd-i2c: specify max

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Message-ID: <20250702152618.GU10134@google.com>
Date: Wed, 2 Jul 2025 16:26:18 +0100
From: Lee Jones <lee@...nel.org>
To: Alex Elder <elder@...cstar.com>
Cc: lgirdwood@...il.com, broonie@...nel.org, alexandre.belloni@...tlin.com,
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	mat.jonczyk@...pl, dlan@...too.org, paul.walmsley@...ive.com,
	palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr,
	troymitchell988@...il.com, guodong@...cstar.com,
	linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/8] mfd: simple-mfd-i2c: specify max_register

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@...cstar.com>
> Suggested-by: Lee Jones <lee@...nel.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]