linux-kernel - Re: [PATCH 9/9] backlight: atmel-pwm-bl: use gpio_request

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Message-ID: <20131029132018.GC29615@localhost>
Date:	Tue, 29 Oct 2013 14:20:18 +0100
From:	Johan Hovold <jhovold@...il.com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Johan Hovold <jhovold@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jingoo Han <jg1.han@...sung.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 9/9] backlight: atmel-pwm-bl: use gpio_request_one

On Fri, Oct 25, 2013 at 01:15:43PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 11:55 Wed 23 Oct     , Johan Hovold wrote:
> > Use devm_gpio_request_one rather than requesting and setting direction
> > in two calls.
> 
> this is the same I do not see any advantage

It removes one error path.

> and as I said for ather backligth It's wrong to enable or disable it at probe
> as the bootloader might have already enable it for splash screen

I agree with you on that, and it's actually the reason for the below
clean up. I use a second patch:

        if (gpio_is_valid(pwmbl->gpio_on)) {
-               /* Turn display off by default. */
-               if (pdata->on_active_low)
+               /* Turn display off unless already enabled. */
+               if (pdata->gpio_on_enabled ^ pdata->on_active_low)
                        flags = GPIOF_OUT_INIT_HIGH;
                else
                        flags = GPIOF_OUT_INIT_LOW;

to make sure the driver does not temporarily disable the backlight at
probe.

Decided not to submit it as part of this series when I realised that
several other backlight drivers did the same, but perhaps I should?

Thanks,
Johan

> > 
> > Acked-by: Jingoo Han <jg1.han@...sung.com>:w
> > Signed-off-by: Johan Hovold <jhovold@...il.com>
> > ---
> >  drivers/video/backlight/atmel-pwm-bl.c | 15 ++++++++-------
> >  1 file changed, 8 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/video/backlight/atmel-pwm-bl.c b/drivers/video/backlight/atmel-pwm-bl.c
> > index 1277e0c..5ea2517 100644
> > --- a/drivers/video/backlight/atmel-pwm-bl.c
> > +++ b/drivers/video/backlight/atmel-pwm-bl.c
> > @@ -124,6 +124,7 @@ static int atmel_pwm_bl_probe(struct platform_device *pdev)
> >  	const struct atmel_pwm_bl_platform_data *pdata;
> >  	struct backlight_device *bldev;
> >  	struct atmel_pwm_bl *pwmbl;
> > +	int flags;
> >  	int retval;
> >  
> >  	pdata = dev_get_platdata(&pdev->dev);
> > @@ -149,14 +150,14 @@ static int atmel_pwm_bl_probe(struct platform_device *pdev)
> >  		return retval;
> >  
> >  	if (gpio_is_valid(pwmbl->gpio_on)) {
> > -		retval = devm_gpio_request(&pdev->dev, pwmbl->gpio_on,
> > -					"gpio_atmel_pwm_bl");
> > -		if (retval)
> > -			goto err_free_pwm;
> > -
> >  		/* Turn display off by default. */
> > -		retval = gpio_direction_output(pwmbl->gpio_on,
> > -				0 ^ pdata->on_active_low);
> > +		if (pdata->on_active_low)
> > +			flags = GPIOF_OUT_INIT_HIGH;
> > +		else
> > +			flags = GPIOF_OUT_INIT_LOW;
> > +
> > +		retval = devm_gpio_request_one(&pdev->dev, pwmbl->gpio_on,
> > +						flags, "gpio_atmel_pwm_bl");
> >  		if (retval)
> >  			goto err_free_pwm;
> >  	}
> > -- 
> > 1.8.4
> > 
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