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

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Date:	Fri, 13 Mar 2015 20:21:37 +0100
From:	Thomas Niederprüm <niederp@...sik.uni-kl.de>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	<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.

Am Tue, 10 Mar 2015 12:49:19 +0200
schrieb Tomi Valkeinen <tomi.valkeinen@...com>:

> 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?

I just gave the backlight-class a try and it works like a charm. I
will include it in v4 and drop the sysfs handles instead. Thanks for the
hint!

Thomas

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