linux-kernel - Re: [PATCH v2 2/3] backlight: tdo24m: add the reset line gpio

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Date:   Sat, 16 Dec 2017 12:39:50 +0100
From:   Robert Jarzmik <robert.jarzmik@...e.fr>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] backlight: tdo24m: add the reset line gpio

Daniel Thompson <daniel.thompson@...aro.org> writes:

> On Fri, Oct 13, 2017 at 09:42:48PM +0200, Robert Jarzmik wrote:
>> The Toppoly panels have a global reset line. Add an optional gpio
>> control for this line, for platforms which have the ability to drive it.
>> 
>> Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
>> ---
>>  drivers/video/backlight/tdo24m.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/drivers/video/backlight/tdo24m.c b/drivers/video/backlight/tdo24m.c
>> index e4bd63e9db6b..e4b2dfabf192 100644
>> --- a/drivers/video/backlight/tdo24m.c
>> +++ b/drivers/video/backlight/tdo24m.c
>> @@ -10,6 +10,7 @@
>>   */
>>  
>>  #include <linux/module.h>
>> +#include <linux/gpio/consumer.h>
>>  #include <linux/kernel.h>
>>  #include <linux/init.h>
>>  #include <linux/device.h>
>> @@ -32,6 +33,7 @@ struct tdo24m {
>>  	struct spi_message	msg;
>>  	struct spi_transfer	xfer;
>>  	uint8_t			*buf;
>> +	struct gpio_desc	*xres;
>
> Why do we need a write-only variable?
It's written to by devm_gpiod_get() below.

>> +	lcd->xres = devm_gpiod_get(&spi->dev, "reset", GPIOD_OUT_LOW);
>
> devm_gpiod_get_optional() would be better, if only for its commenting
> value.
Yes, you're perfectly right.

> Also, this adds a new optional property, doesn't the devicetree binding 
> docs need to be update to match this?
Ah yes, that too. I'll add it for v3.

Cheers.

-- 
Robert