linux-kernel - Re: [PATCH v8 01/13] mfd: add simple regmap based I2C driver

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Date:   Wed, 19 Aug 2020 11:50:29 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v8 01/13] mfd: add simple regmap based I2C driver

On Thu, 13 Aug 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@...le.cc>
> ---
> Changes since v7:
>  - none
> 
> Changes since v6:
>  - added SIMPLE_MFD_I2C help text
>  - revised description in module header
> 
> Changes since v5:
>  - removed "select MFD_CORE" in Kconfig
>  - removed help text in Kconfig, we assume that the users of this
>    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          | 12 ++++++++
>  drivers/mfd/Makefile         |  1 +
>  drivers/mfd/simple-mfd-i2c.c | 56 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 69 insertions(+)
>  create mode 100644 drivers/mfd/simple-mfd-i2c.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 33df0837ab41..6e1a38944d28 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1162,6 +1162,18 @@ 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
> +	help
> +	  This driver creates a single register map with the intention for it
> +	  to be shared by all sub-devices.
> +
> +	  Once the register map has been successfully initialised, any
> +	  sub-devices represented by child nodes in Device Tree will be
> +	  subsequently registered.
> +
>  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..09b40ebfdf07
> --- /dev/null
> +++ b/drivers/mfd/simple-mfd-i2c.c
> @@ -0,0 +1,56 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Simple MFD - I2C
> + *
> + * 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.

Nit: "in order *to* reference it"

Once fixed, please add my:

For my own reference (apply this as-is to your sign-off block):

  Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>

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