Re: [PATCH v2 1/1] mfd: simple-mfd-i2c: Add support for registering devices via MFD cells

[Alistair Francis <alistair23@gmail.com>]

On Thu, Aug 5, 2021 at 6:56 PM Lee Jones <lee.jones@linaro.org> wrote:
>
> 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@walle.cc>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Alistair Francis <alistair23@gmail.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
> v2:
>  - Check for empty of_device_id .data entry
>
>  drivers/mfd/simple-mfd-i2c.c | 41 +++++++++++++++++++++++++++++-------
>  drivers/mfd/simple-mfd-i2c.h | 32 ++++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+), 8 deletions(-)
>  create mode 100644 drivers/mfd/simple-mfd-i2c.h
>
> diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
> index 87f684cff9a17..583e8c7924af0 100644
> --- a/drivers/mfd/simple-mfd-i2c.c
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -2,39 +2,64 @@
>  /*
>   * Simple MFD - I2C
>   *
> + * Author(s):
> + *     Michael Walle <michael@walle.cc>
> + *     Lee Jones <lee.jones@linaro.org>
> + *
>   * This driver creates a single register map with the intention for it to be
>   * shared by all sub-devices.  Children can use their parent's device structure
>   * (dev.parent) in order to reference it.
>   *
>   * Once the register map has been successfully initialised, any sub-devices
> - * represented by child nodes in Device Tree will be subsequently registered.
> + * represented by child nodes in Device Tree or via the MFD cells in this file
> + * will be subsequently registered.
>   */
>
>  #include <linux/i2c.h>
>  #include <linux/kernel.h>
> +#include <linux/mfd/core.h>
>  #include <linux/module.h>
>  #include <linux/of_platform.h>
>  #include <linux/regmap.h>
>
> -static const struct regmap_config simple_regmap_config = {
> +#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 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 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 = 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 no MFD cells are spedified, use register the DT child nodes instead */
> +       if (!simple_mfd_data || !simple_mfd_data->mfd_cell)
> +               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)

Shouldn't this be `if (ret)` instead?

With that changed this works for me as well:

Reviewed-by: Alistair Francis <alistair@alistair23.me>
Tested-by: Alistair Francis <alistair@alistair23.me>

Alistair

> +               dev_err(&i2c->dev, "Failed to add child devices\n");
> +
> +       return ret;
>  }
>
>  static const struct of_device_id simple_mfd_i2c_of_match[] = {
> diff --git a/drivers/mfd/simple-mfd-i2c.h b/drivers/mfd/simple-mfd-i2c.h
> new file mode 100644
> index 0000000000000..7cb2bdd347d97
> --- /dev/null
> +++ b/drivers/mfd/simple-mfd-i2c.h
> @@ -0,0 +1,32 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Simple MFD - I2C
> + *
> + * Author: Lee Jones <lee.jones@linaro.org>
> + *
> + * This driver creates a single register map with the intention for it to be
> + * shared by all sub-devices.  Children can use their parent's device structure
> + * (dev.parent) in order to reference it.
> + *
> + * This driver creates a single register map with the intention for it to be
> + * shared by all sub-devices.  Children can use their parent's device structure
> + * (dev.parent) in order to reference it.
> + *
> + * Once the register map has been successfully initialised, any sub-devices
> + * represented by child nodes in Device Tree or via the MFD cells in the
> + * associated C file will be subsequently registered.
> + */
> +
> +#ifndef __MFD_SIMPLE_MFD_I2C_H
> +#define __MFD_SIMPLE_MFD_I2C_H
> +
> +#include <linux/mfd/core.h>
> +#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;
> +};
> +
> +#endif /* __MFD_SIMPLE_MFD_I2C_H */
> --
> 2.32.0.605.g8dce9f2422-goog
>

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