linux-kernel - Re: [PATCH 7/8] fbdev: ssd1307fb: Add sysfs handles to expose contrast and dim setting to userspace.

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Date:	Tue, 10 Mar 2015 12:49:19 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Thomas Niederprüm <niederp@...sik.uni-kl.de>
CC:	<linux-fbdev@...r.kernel.org>, <plagnioj@...osoft.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/8] fbdev: ssd1307fb: Add sysfs handles to expose contrast
 and dim setting to userspace.

On 09/02/15 10:52, Maxime Ripard wrote:
> On Sat, Feb 07, 2015 at 05:42:44PM +0100, Thomas Niederprüm wrote:
>>>> +static struct device_attribute device_attrs[] = {
>>>> +	__ATTR(contrast, S_IRUGO|S_IWUSR, show_contrast,
>>>> store_contrast),
>>>> +	__ATTR(dim, S_IRUGO|S_IWUSR, show_dim, store_dim),
>>>> +
>>>> +};
>>>> +
>>>
>>> I would have thought this was something accessible through the
>>> framebuffer ioctl.
>>>
>>> Apparently it's not, at least for the contrast, so maybe it should be
>>> added there, instead of doing it for a single driver?
>>
>> I think the contrast setting for an OLED display is much like the
>> backlight setting for LCD panel. Since there is also no ioctl to set
>> the backlight of an LCD I wonder if the contrast of an OLED should have
>> one.
> 
> It's too much of framebuffer interface debate for me here. Tomi?

We have backlight and contrast already in backlight-class and lcd-class
(drivers/video/backlight/backlight.c and drivers/video/backlight/lcd.c).
Are those something that could be used here instead of custom sysfs files?

 Tomi



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