Re: [PATCH v6 01/13] mfd: add simple regmap based I2C driver

[Michael Walle]

Am 2020-07-28 09:19, schrieb Lee Jones:
> 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@xxxxxxxx>
> > ---
> > 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.

What is the use to describe the symbol, if it is not user selectable?
I'm not aware this is done anywhere in the kernel, am I missing
something?

> >    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.

See above.

> >  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

ok.

> > + * 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.

Should this be appended or should it replace my paragraph? If its the 
latter,
the "enumeration of the children" is missing.

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

Why would you remove information about the intention of this driver? If 
someone
looks for a place to implement its SPI/I3C/Slimbus MFD driver this might 
come
in handy.

-michael