linux-kernel - Re: [PATCH v3 3/3] pwm: New driver to support PWM driven LEDs on TWL4030/6030 series of PMICs

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Date:	Mon, 26 Nov 2012 10:17:57 +0100
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Tero Kristo <t-kristo@...com>,
	Grazvydas Ignotas <notasas@...il.com>,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v3 3/3] pwm: New driver to support PWM driven LEDs on
 TWL4030/6030 series of PMICs

On Mon, Nov 26, 2012 at 09:30:03AM +0100, Peter Ujfalusi wrote:
> On 11/23/2012 04:04 PM, Thierry Reding wrote:
> > On Tue, Nov 20, 2012 at 10:56:22AM +0100, Peter Ujfalusi wrote:
> >> The driver supports the following LED outputs as generic PWM driver:
> >> TWL4030 LEDA and LEDB (PWMA and PWMB)
> >> TWL6030 Charging indicator LED (PWM LED)
> >>
> >> On TWL6030 when the PWM requested LED is configured to be controlled by SW.
> >> In this case the user can enable/disable and set the duty period freely.
> >> When the PWM has been freed, the LED driver is put back to HW control.
> >>
> >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> >> ---
> >>  drivers/pwm/Kconfig       |  10 ++
> >>  drivers/pwm/Makefile      |   1 +
> >>  drivers/pwm/pwm-twl-led.c | 303 ++++++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 314 insertions(+)
> >>  create mode 100644 drivers/pwm/pwm-twl-led.c
> > 
> > Doesn't this belong in the drivers/leds subsystem? Besides that, the
> > same comments as for the previous patch apply. One additional note
> > below.
> 
> The PINs itself are called as LED but they are PWMs at the end. If we
> represent them as PWMs they can be used for different purposes which is going
> to be needed for example in BeagleBoard, where the LEDA (PWMA) is used as a
> GPO to enable/disable the USB host power.

Heh, that's an interesting use-case for a PWM. =)

> Also the removed 'twl6030-pwm' driver was only controlled the LED part of twl6030.
> With this series I enable the use of the PWMs and the PWMs behind of the LED
> functions to give us flexibility on how we are using them.

Alright, we can keep it in the PWM subsystem then.

> >> +static struct platform_driver twl_pwmled_driver = {
> >> +	.driver = {
> >> +		.name = "twl-pwmled",
> >> +		.of_match_table = of_match_ptr(twl_pwmled_of_match),
> >> +	},
> >> +	.probe = twl_pwmled_probe,
> >> +	.remove = __devexit_p(twl_pwmled_remove),
> > 
> > You didn't annotate twl_pwmled_remove() with __devexit, so __devexit_p
> > isn't needed here either.
> 
> Oh yes, I have also received patches from a series which removes the
> _devexit_p() from the kernel.
> But should the __devexit need to be added to the remove function?

__devexit_p without a corresponding __devexit doesn't make sense. But as
all of __devinit, __devexit and __devexit_p will be removed sooner or
later, new code just shouldn't bother adding it. In this case, just drop
__devexit_p.

Thierry

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