linux-kernel - Re: [PATCH v7 2/8] mfd: simple-mfd-i2c: specify max

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Message-ID: <20250710092448.GA1431498@google.com>
Date: Thu, 10 Jul 2025 10:24:48 +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 v7 2/8] mfd: simple-mfd-i2c: specify max_register

On Wed, 02 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 use this
> option, Lee Jones suggested allowing just the max_register value
> to be specified in the simple_mfd_data structure.
> 
> Signed-off-by: Alex Elder <elder@...cstar.com>
> Suggested-by: Lee Jones <lee@...nel.org>
> ---
> v2: - Allow max_register *and* regmap_config to be supplied
> 
>  drivers/mfd/simple-mfd-i2c.c | 15 ++++++++++++---
>  drivers/mfd/simple-mfd-i2c.h |  1 +
>  2 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
> index 22159913bea03..3f959f4f98261 100644
> --- a/drivers/mfd/simple-mfd-i2c.c
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -33,16 +33,25 @@ 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 config;

Why do we need another regmap_config?

Can't we just remove the const and make use of the one above?

>  	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)
> +	if (simple_mfd_data) {
> +		if (simple_mfd_data->regmap_config)
> +			config = *simple_mfd_data->regmap_config;

			regmap_config = simple_mfd_data->regmap_config;

> +		else
> +			config = regmap_config_8r_8v;

			regmap_config = &regmap_config_8r_8v;
> +
> +		if (simple_mfd_data->max_register)
> +			config.max_register = simple_mfd_data->max_register;
> +		regmap_config = &config;
> +	} else {
>  		regmap_config = &regmap_config_8r_8v;

I suspect we don't need to have this line twice.

Either re-jig the if () above (I suspect this explains the existing
complexity [multiple conditions]) or pre-set regmap_config to
regmap_config_8r_8v and only over-write it if the conditions are met.

> -	else -		regmap_config = simple_mfd_data->regmap_config;
> +	}
>  
>  	regmap = devm_regmap_init_i2c(i2c, regmap_config); if
>  	(IS_ERR(regmap)) diff --git a/drivers/mfd/simple-mfd-i2c.h
>  	b/drivers/mfd/simple-mfd-i2c.h index
>  	7cb2bdd347d97..706b6f53155ff 100644 ---
>  	a/drivers/mfd/simple-mfd-i2c.h +++
>  	b/drivers/mfd/simple-mfd-i2c.h @@ -27,6 +27,7 @@ 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]