linux-kernel - Re: [PATCH 1/1] mfd: simple-mfd-i2c: Add support for registering devices via MFD cells

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Message-ID: <328e69d4d6d57b101af1ab1346b0809f@walle.cc>
Date:   Thu, 05 Aug 2021 09:05:57 +0200
From:   Michael Walle <michael@...le.cc>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 1/1] mfd: simple-mfd-i2c: Add support for registering
 devices via MFD cells

Hi Lee,

Am 2021-08-04 16:37, schrieb Lee Jones:
> More devices are cropping up requiring only Regmap initialisation and
> child registration functionality.  We currently only support that if
> all required devices are represented by their own Device Tree nodes
> complete with compatible strings.
> 
> However, not everyone is happy with adding empty nodes that provide no
> additional device information into the Device Tree.
> 
> Rather than have a plethora of mostly empty, function-less drivers in
> MFD, we'll support those simple cases in here instead via MFD cells.
> 
> Cc: Michael Walle <michael@...le.cc>
> Cc: Mark Brown <broonie@...nel.org>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
> 
> Michael, could you please test this on your platform to ensure I
>          didn't break anything please?
> 

I'm getting a null pointer dereference.

[..]

>  static int simple_mfd_i2c_probe(struct i2c_client *i2c)
>  {
> -	const struct regmap_config *config;
> +	const struct simple_mfd_data *simple_mfd_data;
> +	const struct regmap_config *regmap_config;
>  	struct regmap *regmap;
> +	int ret;
> +
> +	simple_mfd_data = device_get_match_data(&i2c->dev);
> 
> -	config = device_get_match_data(&i2c->dev);
> -	if (!config)
> -		config = &simple_regmap_config;
> +	if (simple_mfd_data->regmap_config)

simple_mfd_data might be NULL.

> +		regmap_config = simple_mfd_data->regmap_config;
> +	else
> +		regmap_config = &regmap_config_8r_8v;
> 
> -	regmap = devm_regmap_init_i2c(i2c, config);
> +	regmap = devm_regmap_init_i2c(i2c, regmap_config);
>  	if (IS_ERR(regmap))
>  		return PTR_ERR(regmap);
> 
> -	return devm_of_platform_populate(&i2c->dev);
> +	if (!simple_mfd_data->mfd_cell)

likewise

> +		return devm_of_platform_populate(&i2c->dev);
> +
> +	ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO,
> +				   simple_mfd_data->mfd_cell,
> +				   simple_mfd_data->mfd_cell_size,
> +				   NULL, 0, NULL);
> +	if (!ret)
> +		dev_err(&i2c->dev, "Failed to add child devices\n");
> +
> +	return ret;
>  }

-michael