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

Michael Walle
2020-07-28T07:42:34Z

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@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.

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