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SubjectRe: [PATCH v6 01/13] mfd: add simple regmap based I2C driver
On Sun, 26 Jul 2020, Michael Walle wrote:

> There are I2C devices which contain several different functions but
> doesn't require any special access functions. For these kind of drivers
> an I2C regmap should be enough.
>
> Create an I2C driver which creates an I2C regmap and enumerates its
> children. If a device wants to use this as its MFD core driver, it has
> to add an individual compatible string. It may provide its own regmap
> configuration.
>
> Subdevices can use dev_get_regmap() on the parent to get their regmap
> instance.
>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
> Changes since v5:
> - removed "select MFD_CORE" in Kconfig
> - removed help text in Kconfig, we assume that the users of this

That's the opposite of what I asked for.

> driver will have a "select MFD_SIMPLE_MFD_I2C". Instead added
> a small description to the driver itself.
> - removed "struct simple_mfd_i2c_config" and use regmap_config
> directly
> - changed builtin_i2c_driver() to module_i2c_driver(), added
> MODULE_ boilerplate
> - cleaned up the included files
>
> Changes since v4:
> - new patch. Lee, please bear with me. I didn't want to delay the
> new version (where a lot of remarks on the other patches were
> addressed) even more, just because we haven't figured out how
> to deal with the MFD part. So for now, I've included this one.
>
> drivers/mfd/Kconfig | 5 ++++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/simple-mfd-i2c.c | 55 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 61 insertions(+)
> create mode 100644 drivers/mfd/simple-mfd-i2c.c
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 33df0837ab41..c08539c7a166 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1162,6 +1162,11 @@ config MFD_SI476X_CORE
> To compile this driver as a module, choose M here: the
> module will be called si476x-core.
>
> +config MFD_SIMPLE_MFD_I2C
> + tristate
> + depends on I2C
> + select REGMAP_I2C

Please provide a full help.

> config MFD_SM501
> tristate "Silicon Motion SM501"
> depends on HAS_DMA
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index a60e5f835283..78d24a3e7c9e 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -264,3 +264,4 @@ obj-$(CONFIG_MFD_STMFX) += stmfx.o
> obj-$(CONFIG_MFD_KHADAS_MCU) += khadas-mcu.o
>
> obj-$(CONFIG_SGI_MFD_IOC3) += ioc3.o
> +obj-$(CONFIG_MFD_SIMPLE_MFD_I2C) += simple-mfd-i2c.o
> diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
> new file mode 100644
> index 000000000000..45090ddad104
> --- /dev/null
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * A very simple I2C MFD driver

Simple MFD - I2C

> + * The driver enumerates its children and registers a common regmap. Use
> + * dev_get_regmap(pdev->dev.parent, NULL) in the child nodes to fetch that
> + * regmap instance.

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 reference it.

> + * In the future this driver might be extended to support also other interfaces
> + * like SPI etc.

Remove this please.

> + */

'\n' here.

> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/regmap.h>
> +
> +static const struct regmap_config simple_regmap_config = {
> + .reg_bits = 8,
> + .val_bits = 8,
> +};
> +
> +static int simple_mfd_i2c_probe(struct i2c_client *i2c)
> +{
> + const struct regmap_config *config;
> + struct regmap *regmap;
> +
> + config = device_get_match_data(&i2c->dev);
> + if (!config)
> + config = &simple_regmap_config;
> +
> + regmap = devm_regmap_init_i2c(i2c, config);
> + if (IS_ERR(regmap))
> + return PTR_ERR(regmap);
> +
> + return devm_of_platform_populate(&i2c->dev);
> +}
> +
> +static const struct of_device_id simple_mfd_i2c_of_match[] = {
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, simple_mfd_i2c_of_match);
> +
> +static struct i2c_driver simple_mfd_i2c_driver = {
> + .probe_new = simple_mfd_i2c_probe,
> + .driver = {
> + .name = "simple-mfd-i2c",
> + .of_match_table = simple_mfd_i2c_of_match,
> + },
> +};
> +module_i2c_driver(simple_mfd_i2c_driver);
> +
> +MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
> +MODULE_DESCRIPTION("Simple I2C MFD driver");

Simple MFD - I2C driver

> +MODULE_LICENSE("GPL v2");

--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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