From: Daniel Thompson <daniel.thompson@linaro.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: mark.rutland@arm.com, jingoohan1@gmail.com,
tomi.valkeinen@ti.com, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, robh+dt@kernel.org,
jacek.anaszewski@gmail.com, Jean-Jacques Hiblot <jjhiblot@ti.com>,
lee.jones@linaro.org, linux-leds@vger.kernel.org, dmurphy@ti.com
Subject: Re: [PATCH 0/4] Add a generic driver for LED-based backlight
Date: Fri, 5 Jul 2019 11:29:59 +0100 [thread overview]
Message-ID: <20190705102959.cmqhzpzikqjsydlx@holly.lan> (raw)
In-Reply-To: <20190705101434.fw5rpctnqt6dwg6e@devuan>
On Fri, Jul 05, 2019 at 12:14:34PM +0200, Pavel Machek wrote:
> On Mon 2019-07-01 17:14:19, Jean-Jacques Hiblot wrote:
> > This series aims to add a led-backlight driver, similar to pwm-backlight,
> > but using a LED class device underneath.
> >
> > A few years ago (2015), Tomi Valkeinen posted a series implementing a
> > backlight driver on top of a LED device:
> > https://patchwork.kernel.org/patch/7293991/
> > https://patchwork.kernel.org/patch/7294001/
> > https://patchwork.kernel.org/patch/7293981/
> >
> > The discussion stopped because Tomi lacked the time to work on it.
> >
> > This series takes it from there and implements the binding that was
> > discussed in https://patchwork.kernel.org/patch/7293991/. In this new
> > binding the backlight device is a child of the LED controller instead of
> > being another platform device that uses a phandle to reference a LED.
>
> Other option would be to have backlight trigger. What are
> advantages/disadvantages relative to that?
I spent a little time thinking about that during the recent round of
reviews.
My rough thoughts were that LED triggers would be a good way to
handle it in the kernel code and would trivially solve a backlight
composed of multiple LED devices (since all could attach to the same
trigger). However I think it would be difficult to use the existing DT
bindings for triggers to express things like brightness curves and to
handle systems with multiple heads.
I'm not *too* worried about conflict with the existing backlight trigger
(which isn't actually a backlight... just a hook into the framebuffer
code to operate a binary LED). People like Daniel Vetter are
labouring diligently to get rid of the notifier it depends on so turning
it into a proper backlight device would probably help with that effort.
Anyhow... having thought the above I then shook myself a bit and
figured it was more important to focus on sane bindings that on what
the kernel does under the covers to realize them ;-) and decided to keep
quiet until the next set of bindings is proposed.
However... since you asked...
Daniel.
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WARNING: multiple messages have this Message-ID (diff)
From: Daniel Thompson <daniel.thompson@linaro.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: Jean-Jacques Hiblot <jjhiblot@ti.com>,
jacek.anaszewski@gmail.com, robh+dt@kernel.org,
mark.rutland@arm.com, lee.jones@linaro.org, jingoohan1@gmail.com,
dmurphy@ti.com, linux-leds@vger.kernel.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
tomi.valkeinen@ti.com
Subject: Re: [PATCH 0/4] Add a generic driver for LED-based backlight
Date: Fri, 5 Jul 2019 11:29:59 +0100 [thread overview]
Message-ID: <20190705102959.cmqhzpzikqjsydlx@holly.lan> (raw)
Message-ID: <20190705102959.bgDFbKcWOlMggg1PoBJiLW0SHupmgftqd9ofRqjixmQ@z> (raw)
In-Reply-To: <20190705101434.fw5rpctnqt6dwg6e@devuan>
On Fri, Jul 05, 2019 at 12:14:34PM +0200, Pavel Machek wrote:
> On Mon 2019-07-01 17:14:19, Jean-Jacques Hiblot wrote:
> > This series aims to add a led-backlight driver, similar to pwm-backlight,
> > but using a LED class device underneath.
> >
> > A few years ago (2015), Tomi Valkeinen posted a series implementing a
> > backlight driver on top of a LED device:
> > https://patchwork.kernel.org/patch/7293991/
> > https://patchwork.kernel.org/patch/7294001/
> > https://patchwork.kernel.org/patch/7293981/
> >
> > The discussion stopped because Tomi lacked the time to work on it.
> >
> > This series takes it from there and implements the binding that was
> > discussed in https://patchwork.kernel.org/patch/7293991/. In this new
> > binding the backlight device is a child of the LED controller instead of
> > being another platform device that uses a phandle to reference a LED.
>
> Other option would be to have backlight trigger. What are
> advantages/disadvantages relative to that?
I spent a little time thinking about that during the recent round of
reviews.
My rough thoughts were that LED triggers would be a good way to
handle it in the kernel code and would trivially solve a backlight
composed of multiple LED devices (since all could attach to the same
trigger). However I think it would be difficult to use the existing DT
bindings for triggers to express things like brightness curves and to
handle systems with multiple heads.
I'm not *too* worried about conflict with the existing backlight trigger
(which isn't actually a backlight... just a hook into the framebuffer
code to operate a binary LED). People like Daniel Vetter are
labouring diligently to get rid of the notifier it depends on so turning
it into a proper backlight device would probably help with that effort.
Anyhow... having thought the above I then shook myself a bit and
figured it was more important to focus on sane bindings that on what
the kernel does under the covers to realize them ;-) and decided to keep
quiet until the next set of bindings is proposed.
However... since you asked...
Daniel.
next prev parent reply other threads:[~2019-07-05 10:29 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 15:14 [PATCH 0/4] Add a generic driver for LED-based backlight Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 1/4] leds: of: create a child device if the LED node contains a "compatible" string Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 2/4] devicetree: Update led binding Jean-Jacques Hiblot
2019-07-01 15:20 ` Dan Murphy
2019-07-01 15:14 ` [PATCH 3/4] backlight: add led-backlight driver Jean-Jacques Hiblot
2019-07-02 9:54 ` Daniel Thompson
2019-07-02 10:59 ` Jean-Jacques Hiblot
2019-07-02 13:04 ` Daniel Thompson
2019-07-02 15:17 ` Jean-Jacques Hiblot
2019-07-03 9:44 ` Daniel Thompson
2019-07-03 10:02 ` Jean-Jacques Hiblot
2019-07-05 10:08 ` Pavel Machek
2019-07-05 10:08 ` Pavel Machek
2019-07-05 10:33 ` Jean-Jacques Hiblot
2019-07-05 10:33 ` Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 4/4] devicetree: Add led-backlight binding Jean-Jacques Hiblot
2019-07-02 9:58 ` Daniel Thompson
2019-07-02 11:11 ` Jean-Jacques Hiblot
2019-07-05 10:11 ` Pavel Machek
2019-07-05 10:11 ` Pavel Machek
2019-07-05 10:14 ` [PATCH 0/4] Add a generic driver for LED-based backlight Pavel Machek
2019-07-05 10:14 ` Pavel Machek
2019-07-05 10:29 ` Daniel Thompson [this message]
2019-07-05 10:29 ` Daniel Thompson
2019-07-05 11:34 ` Jean-Jacques Hiblot
2019-07-05 11:34 ` Jean-Jacques Hiblot
2019-07-05 23:23 ` Sebastian Reichel
2019-07-05 23:23 ` Sebastian Reichel
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