linux-kernel - Re: [PATCH 05/10] ARM: SAMSUNG: Initialize PWM backlight enable

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Date:	Tue, 01 Oct 2013 14:58:22 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Thierry Reding <thierry.reding@...il.com>
CC:	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	Eric Miao <eric.y.miao@...il.com>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Ben Dooks <ben-linux@...ff.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Guan Xuetao <gxt@...c.pku.edu.cn>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
	openezx-devel@...ts.openezx.org, linux-samsung-soc@...r.kernel.org,
	linux-sh@...r.kernel.org, linux-pwm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/10] ARM: SAMSUNG: Initialize PWM backlight enable_gpio
 field

On 10/01/2013 02:43 PM, Thierry Reding wrote:
> On Tue, Oct 01, 2013 at 12:31:04PM -0600, Stephen Warren wrote:
>> On 09/23/2013 03:41 PM, Thierry Reding wrote:
>>> The GPIO API defines 0 as being a valid GPIO number, so this
>>> field needs to be initialized explicitly.
>> 
>>> static void __init smdkv210_map_io(void)
>> 
>>> @@ -70,6 +70,7 @@ static struct samsung_bl_drvdata
>>> samsung_dfl_bl_data __initdata = { .max_brightness = 255, 
>>> .dft_brightness = 255, .pwm_period_ns  = 78770, +		.enable_gpio
>>> = -1, .init           = samsung_bl_init, .exit           =
>>> samsung_bl_exit, }, @@ -121,6 +122,10 @@ void __init
>>> samsung_bl_set(struct samsung_bl_gpio_info *gpio_info, 
>>> samsung_bl_data->lth_brightness = bl_data->lth_brightness; if
>>> (bl_data->pwm_period_ns) samsung_bl_data->pwm_period_ns =
>>> bl_data->pwm_period_ns; +	if (bl_data->enable_gpio) +
>>> samsung_bl_data->enable_gpio = bl_data->enable_gpio; +	if
>>> (bl_data->enable_gpio_flags) +
>>> samsung_bl_data->enable_gpio_flags =
>>> bl_data->enable_gpio_flags;
>> 
>> Won't this cause the core pwm_bl driver to request/manipulate the
>> GPIO, whereas this driver already does that inside the
>> samsung_bl_init/exit callbacks? I think you either need to adjust
>> those callbacks, or not set the new standard GPIO property in
>> samsung_bl_data.
> 
> I don't think so. The samsung_bl_data is a copy of
> samsung_dfl_bl_data augmented by board-specific settings. So in
> fact copying these values here is essential to allow boards to
> override the enable_gpio and flags fields. Currently no board sets
> the enable_gpio to a valid GPIO so it's all still handled by the
> callbacks only.

Oh yes, you're right. I was confusing the new enable_gpio field in
pwm_bl's platform data with some other field in a custom data structure.

One minor point though:

>>> +	if (bl_data->enable_gpio) +		samsung_bl_data->enable_gpio =
>>> bl_data->enable_gpio;

That assumes that enable_gpio==0 means "none", whereas you've gone to
great pains in the rest of the series to allow 0 to be a valid GPIO
ID. right now, the default value of samsung_bl_data->enable_gpio is
-1, and if !bl_data->enable_gpio, that value won't be propagated across.
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