Re: [PATCH v4 2/2] rtc: max31335: add driver support

[Guenter Roeck]

On 11/1/23 08:21, Miclaus, Antoniu wrote:
> > On Wed, Nov 01, 2023 at 11:48:14AM +0200, Antoniu Miclaus wrote:
> > > RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
> > > Integrated MEMS Resonator.
> > >
> > > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx>
> > > ---
> > > changes in v4:
> > >   - add Kconfig entry for HWMON dependency.
> > >   MAINTAINERS                |   8 +
> > >   drivers/rtc/Kconfig        |  20 +
> > >   drivers/rtc/Makefile       |   1 +
> > >   drivers/rtc/rtc-max31335.c | 765
> > +++++++++++++++++++++++++++++++++++++
> > >   4 files changed, 794 insertions(+)
> > >   create mode 100644 drivers/rtc/rtc-max31335.c
> > >
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index dd5de540ec0b..bc484cb997ab 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -12823,6 +12823,14 @@ F:
> > 	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> > >   F:	Documentation/hwmon/max31827.rst
> > >   F:	drivers/hwmon/max31827.c
> > >
> > > +MAX31335 RTC DRIVER
> > > +M:	Antoniu Miclaus <antoniu.miclaus@xxxxxxxxxx>
> > > +L:	linux-rtc@xxxxxxxxxxxxxxx
> > > +S:	Supported
> > > +W:	https://ez.analog.com/linux-software-drivers
> > > +F:	Documentation/devicetree/bindings/rtc/adi,max31335.yaml
> > > +F:	drivers/rtc/rtc-max31335.c
> > > +
> > >   MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
> > >   L:	linux-hwmon@xxxxxxxxxxxxxxx
> > >   S:	Orphan
> > > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > > index d7502433c78a..360da13fe61b 100644
> > > --- a/drivers/rtc/Kconfig
> > > +++ b/drivers/rtc/Kconfig
> > > @@ -373,6 +373,26 @@ config RTC_DRV_MAX8997
> > >   	  This driver can also be built as a module. If so, the module
> > >   	  will be called rtc-max8997.
> > >
> > > +config RTC_DRV_MAX31335
> > > +	tristate "Analog Devices MAX31335"
> > > +	depends on I2C
> > > +	select REGMAP_I2C
> > > +	help
> > > +	  If you say yes here you get support for the Analog Devices
> > > +	  MAX31335.
> > > +
> > > +	  This driver can also be built as a module. If so, the module
> > > +	  will be called rtc-max31335.
> > > +
> > > +config RTC_DRV_MAX31335_HWMON
> > > +	bool "HWMON support for Analog Devices MAX31335"
> > > +	depends on RTC_DRV_MAX31335 && HWMON
> > > +	depends on !(RTC_DRV_MAX31335=y && HWMON=m)
> > > +	default y
> > > +	help
> > > +	  Say Y here if you want to expose temperature sensor data on
> > > +	  rtc-max31335.
> > > +
> >
> > This isn't used in the driver. Did you test with HWMON=n ?
>
> I need to start thinking a bit more out of the box instead of
> taking other driver approaches as being the only way to go. 😊

There are essentially two options: Either the above, or use
	depends on HWMON || HWMON=n
for RTC_DRV_MAX31335.

In both cases, the driver hwmon code has to be surrounded with #if[def].
Depending on your approach, that will be "#ifdef RTC_DRV_MAX31335_HWMON"
or "#if IS_REACHABLE(HWMON)".

You could also use "depends on HWMON" for RTC_DRV_MAX31335 to avoid the
#ifdef in the driver, but that is normally undesirable.

Guenter