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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: Robin van der Gracht <robin@protonic.nl>,
	Rob Herring <robh+dt@kernel.org>, Miguel Ojeda <ojeda@kernel.org>,
	Paul Burton <paulburton@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	"open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-leds <linux-leds@vger.kernel.org>
Subject: Re: [PATCH 17/17] auxdisplay: ht16k33: Add segment display LED support
Date: Fri, 25 Jun 2021 14:39:40 +0200	[thread overview]
Message-ID: <CAMuHMdWQOQmeoNP8po19m_Fo9d55ur68CqOORX-NGhkLbRAsGg@mail.gmail.com> (raw)
In-Reply-To: <CAMuHMdVF30BCA-7vCiwmKO6KVFhtNLbL+VEW59oxcAfwJ+jXyg@mail.gmail.com>

On Wed, Mar 24, 2021 at 9:31 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Tue, Mar 23, 2021 at 9:40 PM Pavel Machek <pavel@ucw.cz> wrote:
> > > CC linux-leds (which I intended, but forgot to add)
> > >
> > > cover letter at
> > > https://lore.kernel.org/linux-devicetree/20210322144848.1065067-1-geert@linux-m68k.org/

> > > > > +     err = ht16k33_brightness_set(priv, seg->led.brightness);
> > > > >       if (err)
> > > > >               return err;
> > > >
> > > > The LED class can pretty much do what the backlight class can and more.
> > > >
> > > > Maybe we can stop registering a backlight device in the fbdev case and
> > > > register a led device for both. This makes the code cleaner and drops
> > > > a dependency but will break backwards compatibility.
> > > >
> > > > I'd prefer a single solution that covers both use cases, but I'm not
> > > > sure about the 'breaking backwards compatibility' consequence...
> >
> > For new drivers, breaking compatibility should not be a problem.
>
> The dot-matrix support is part of the existing driver, thus subject to
> backwards compatibility.
> Perhaps we can register the LED device for both, and build the backlight
> device on top of the LED device, like "led-backlight" does.  Would that
> work? Or can't the LED no longer be controlled from sysfs (e.g.
> triggers) if it is in use by a backlight driver?

Using "led-backlight", the backlight can no longer be controlled from
sysfs, precluding the use of other triggers incl. hardware blinking.
But a normal LED can be used as a backlight, with ledtrig-backlight,
so that is the most flexible option, but only if no backwards
compatibility is to be considered.


Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

  parent reply	other threads:[~2021-06-25 12:39 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22 14:48 [PATCH 00/17] auxdisplay: ht16k33: Add character display support Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 01/17] uapi: Add <linux/map_to_14segment.h> Geert Uytterhoeven
2021-03-22 17:05   ` Miguel Ojeda
2021-03-22 17:51     ` Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 02/17] dt-bindings: auxdisplay: ht16k33: Document Adafruit segment displays Geert Uytterhoeven
2021-03-22 17:38   ` Rob Herring
2021-03-23  9:12   ` robin
2021-05-18 14:35     ` Geert Uytterhoeven
2021-05-19 10:37       ` Robin van der Gracht
2021-05-19 11:02         ` Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 03/17] auxdisplay: img-ascii-lcd: Fix lock-up when displaying empty string Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 04/17] auxdisplay: img-ascii-lcd: Add helper variable dev Geert Uytterhoeven
2021-03-22 16:59   ` Miguel Ojeda
2021-03-22 17:53     ` Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 05/17] auxdisplay: img-ascii-lcd: Convert device attribute to sysfs_emit() Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 06/17] auxdisplay: Extract character line display core support Geert Uytterhoeven
2021-03-23  8:18   ` robin
2021-03-23  8:52     ` Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 07/17] auxdisplay: linedisp: Use kmemdup_nul() helper Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 08/17] auxdisplay: linedisp: Add support for changing scroll rate Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 09/17] auxdisplay: ht16k33: Use HT16K33_FB_SIZE in ht16k33_initialize() Geert Uytterhoeven
2021-03-23  7:59   ` robin
2021-03-22 14:48 ` [PATCH 10/17] auxdisplay: ht16k33: Remove unneeded error check in keypad probe() Geert Uytterhoeven
2021-03-23  8:08   ` robin
2021-03-22 14:48 ` [PATCH 11/17] auxdisplay: ht16k33: Convert to simple i2c probe function Geert Uytterhoeven
2021-03-23  8:31   ` robin
2021-03-22 14:48 ` [PATCH 12/17] auxdisplay: ht16k33: Add helper variable dev Geert Uytterhoeven
2021-03-23  8:57   ` robin
2021-03-22 14:48 ` [PATCH 13/17] auxdisplay: ht16k33: Move delayed work Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 14/17] auxdisplay: ht16k33: Extract ht16k33_brightness_set() Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 15/17] auxdisplay: ht16k33: Extract frame buffer probing Geert Uytterhoeven
2021-03-22 14:48 ` [PATCH 16/17] auxdisplay: ht16k33: Add support for segment displays Geert Uytterhoeven
2021-03-29  7:08   ` Robin van der Gracht
2021-03-29  7:15     ` Geert Uytterhoeven
2021-03-29  7:30       ` Robin van der Gracht
2021-03-22 14:48 ` [PATCH 17/17] auxdisplay: ht16k33: Add segment display LED support Geert Uytterhoeven
2021-03-23 10:08   ` Robin van der Gracht
2021-03-23 12:32     ` Geert Uytterhoeven
2021-03-23 20:40       ` Pavel Machek
2021-03-24  8:31         ` Geert Uytterhoeven
2021-03-27 22:19           ` Pavel Machek
2021-06-25 12:39           ` Geert Uytterhoeven [this message]
2021-03-22 17:03 ` [PATCH 00/17] auxdisplay: ht16k33: Add character display support Miguel Ojeda

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