Re: [PATCH v7 06/13] pwm: add support for sl28cpld PWM controller

From: Michael Walle <michael@walle.cc>
To: Lee Jones <lee.jones@linaro.org>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org,
	linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Jean Delvare" <jdelvare@suse.com>,
	"Guenter Roeck" <linux@roeck-us.net>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Wim Van Sebroeck" <wim@linux-watchdog.org>,
	"Shawn Guo" <shawnguo@kernel.org>, "Li Yang" <leoyang.li@nxp.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Jason Cooper" <jason@lakedaemon.net>,
	"Marc Zyngier" <maz@kernel.org>,
	"Mark Brown" <broonie@kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Will Deacon" <will@kernel.org>, "Pavel Machek" <pavel@ucw.cz>
Subject: Re: [PATCH v7 06/13] pwm: add support for sl28cpld PWM controller
Date: Mon, 10 Aug 2020 09:31:38 +0200	[thread overview]
Message-ID: <2ca0a3a3f03a1f5b9b2777738824123b@walle.cc> (raw)
In-Reply-To: <20200810071328.GB4411@dell>

Am 2020-08-10 09:13, schrieb Lee Jones:
> On Fri, 07 Aug 2020, Michael Walle wrote:
> 
>> Hi Uwe, Hi Lee,
>> 
>> Am 2020-08-06 10:40, schrieb Uwe Kleine-König:
>> > On Mon, Aug 03, 2020 at 11:35:52AM +0200, Michael Walle wrote:
>> > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>> > > index 7dbcf6973d33..a0d50d70c3b9 100644
>> > > --- a/drivers/pwm/Kconfig
>> > > +++ b/drivers/pwm/Kconfig
>> > > @@ -428,6 +428,16 @@ config PWM_SIFIVE
>> > >  	  To compile this driver as a module, choose M here: the module
>> > >  	  will be called pwm-sifive.
>> > >
>> > > +config PWM_SL28CPLD
>> > > +	tristate "Kontron sl28cpld PWM support"
>> > > +	select MFD_SIMPLE_MFD_I2C
>> >
>> > Is it sensible to present this option to everyone? Maybe
>> >
>> > 	depends on SOME_SYMBOL_ONLY_TRUE_ON_SL28CPLD || COMPILE_TEST
>> 
>> Because there is now no real MFD driver anymore, there is also
>> no symbol for that. The closest would be ARCH_ARM64 but I don't
>> think that is a good idea.
>> 
>> Lee, what do you think about adding a symbol to the MFD, which
>> selects MFD_SIMPLE_MFD_I2C but doesn't enable any C modules?
>> 
>> I.e.
>> config MFD_SL28CPLD
>>     tristate "Kontron sl28cpld"
>>     select MFD_SIMPLE_MFD_I2C
>>     help
>>       Say yes here to add support for the Kontron sl28cpld board
>>       management controller.
>> 
>> Then all the other device driver could depend on the MFD_SL28CPLD
>> symbol.
> 
> You want to add a virtual symbol to prevent having to present a real
> one?  How is that a reasonable solution?

(1) Its a symbol on which all sl28cpld will depend on. Thus they will
     all be hidden if that is not set.
(2) the drivers itself wouldn't need to depend on MFD_SIMPLE_MFD_I2C,
     which is more correct, because they don't have anything to do with
     i2c.

-michael