linux-kernel - Re: [PATCH v8 0/5] auxdisplay: add support for TI LP5812 4x3 Matrix LED driver

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Message-ID: <aBHN+395kaIdbBEm@duo.ucw.cz>
Date: Wed, 30 Apr 2025 09:15:07 +0200
From: Pavel Machek <pavel@....cz>
To: Nam Tran <trannamatk@...il.com>
Cc: andy@...nel.org, geert@...ux-m68k.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org,
	christophe.jaillet@...adoo.fr, corbet@....net,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, florian.fainelli@...adcom.com,
	bcm-kernel-feedback-list@...adcom.com,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v8 0/5] auxdisplay: add support for TI LP5812 4x3 Matrix
 LED driver

Hi!

> > > > Is it intended to be used as a 4x3 matrix, or is this just an internal
> > > > wiring detail, and should it be exposed as 12 individual LEDs instead?
> > > 
> > > The 4×3 matrix is a real and fundamental aspect of the LP5812’s operation.
> > > It is not just an internal wiring detail.
> > > The device adopts a Time-Cross-Multiplexing (TCM) structure, where 4 output
> > > pins control 12 LED dots individually through scanning. Each pin includes
> > > both high-side and low-side drive circuits, meaning matrix multiplexing is
> > > required for proper operation — it cannot be treated as 12 completely
> > > independent LEDs.
> > 
> > Scanning is really a detail.
> > 
> > If this is used as rectangular 4x3 display, then it goes to auxdisplay.
> > 
> > If this is used as a power LED, SD activity LED, capslock and numlock
> > ... placed randomly all around the device, then it goes LED subsystem.
> 
> The LP5812 is used for LED status indication in devices like smart speakers,
> wearables, and routers, not as a structured rectangular display.

Well, IIRC it also supports automated animations, and that does not
make sense on LED indicators. So... what device do _you_ have and how
exactly is it used there?

Best regards,
								Pavel
-- 
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