linux-kernel - Re: Linux support for a 7 segment LED display

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Message-ID: <CAHp75VeGiAWOFgOVjpOCHj0-CGgUYAuGEYmLomn4ydnSVv=_yA@mail.gmail.com>
Date: Fri, 23 Feb 2024 16:44:53 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Chris Packham <Chris.Packham@...iedtelesis.co.nz>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Pavel Machek <pavel@....cz>, 
	"lee@...nel.org" <lee@...nel.org>, "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Linux support for a 7 segment LED display

On Fri, Feb 23, 2024 at 3:01 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Fri, Feb 23, 2024 at 1:36 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Fri, Feb 23, 2024 at 9:52 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > Note that most larger displays are not individual LEDs, but matrices
> > > of LEDs. Do we want to drive/scan them from software, using a
> > > gpio-7seg-matrix driver?
> >
> > LED matrices are the displays (like tinyDRM is for).
>
> TinyDRM is for rectangular matrices.
>
> Multiple 7-segment displays are usually multiplexed using a matrix,
> using 7 (or 8) lines shared by the corresponding segments of all
> displays, and one common line per display.
> https://embedded-lab.com/blog/wp-content/uploads/2011/03/Lab11_Circuit_SevenSegmentMultiplexing.jpg

Yes, that's what I call "dynamic" approach (in my translated
terminology, I dunno the proper English one). With this in mind, you
can read my message(s) above where I referred to it.

--
With Best Regards,
Andy Shevchenko