linux-kernel - Re: [Intel-gfx] [PATCH 6/8] drivers/pwm: Add Crystalcove (CRC) PWM driver

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Date:	Thu, 18 Jun 2015 20:41:56 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	Shobhit Kumar <kumar@...bhit.info>
Cc:	Shobhit Kumar <shobhit.kumar@...el.com>,
	linux-pwm <linux-pwm@...r.kernel.org>,
	Jani Nikula <jani.nikula@...el.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Alexandre Courbot <gnurou@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Povilas Staniulis <wdmonster@...il.com>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-gpio <linux-gpio@...r.kernel.org>,
	Chih-Wei Huang <cwhuang@...roid-x86.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Lee Jones <lee.jones@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [Intel-gfx] [PATCH 6/8] drivers/pwm: Add Crystalcove (CRC) PWM
 driver

Hi Shobhit,

On Thu, 2015-06-18 at 23:24 +0530, Shobhit Kumar wrote:
> On Fri, May 1, 2015 at 2:42 AM, Paul Bolle <pebolle@...cali.nl> wrote:
> > On Wed, 2015-04-29 at 19:30 +0530, Shobhit Kumar wrote:
> >> --- a/drivers/pwm/Kconfig
> >> +++ b/drivers/pwm/Kconfig
> >
> >> +config PWM_CRC
> >> +     bool "Intel Crystalcove (CRC) PWM support"
> >> +     depends on X86 && INTEL_SOC_PMIC
> >> +     help
> >> +       Generic PWM framework driver for Crystalcove (CRC) PMIC based PWM
> >> +       control.
> >
> >> --- a/drivers/pwm/Makefile
> >> +++ b/drivers/pwm/Makefile
> >
> >> +obj-$(CONFIG_PWM_CRC)                += pwm-crc.o
> >
> > PWM_CRC is a bool symbol. So pwm-crc.o can never be part of a module.
> 
> I actually started this as a module but later decided to make it as
> bool because INTEL_SOC_PMIC on which this depends is itself a bool as
> well.

As does GPIO_CRYSTAL_COVE and that's a tristate. So?

> Still it is good to keep the module based initialization.
> Firstly because it causes no harm

If I got a dime for every time people used an argument like that I ... I
could treat myself to an ice cream. A really big ice cream. Hmm, that
doesn't sound too impressive. But still, "causes no harm" is below the
bar for kernel code. Kernel code needs to add value.

> and even though some of the macros
> are pre-processed out, gives info about the driver.

None of which can't be gotten elsewhere (ie, the commit message, or the
file these macro reside in).

> Secondly there
> were discussion on why INTEL_SOC_PMIC is bool (note this driver also
> has module based initialization even when bool).

Yes, there's copy and paste going on even in kernel development.

> I am guessing because
> of some tricky module load order dependencies. If ever that becomes a
> module, this can mostly be unchanged to be loaded as a module.

You put in a macro, or any other bit of code, when it's needed, not
beforehand, "just in case". That's silly.

Thanks,


Paul Bolle

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