linux-kernel - Re: [PATCH v3 4/4] ARM: dts: marvell: Indicate USB activity on x530

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Date: Mon, 4 Mar 2024 21:16:41 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Chris Packham <chris.packham@...iedtelesis.co.nz>, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	andrew@...n.ch, gregory.clement@...tlin.com,
	sebastian.hesselbarth@...il.com, pavel@....cz, lee@...nel.org,
	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 4/4] ARM: dts: marvell: Indicate USB activity on x530

On Mon, Mar 04, 2024 at 08:01:58PM +0100, Geert Uytterhoeven wrote:
> On Mon, Mar 4, 2024 at 7:17 PM Andy Shevchenko
> <andy.shevchenko@...il.com> wrote:
> > On Mon, Mar 4, 2024 at 11:57 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > On Sun, Mar 3, 2024 at 9:43 PM Andy Shevchenko
> > > <andy.shevchenko@...il.com> wrote:

..

> > > So IMHO it would be a bad idea to make the DP mandatory.
> >
> > But I'm not talking about making it mandatory, I'm talking about the
> 
> OK.
> 
> > DP to be used as DP when it _is_ present and wired. If current
> > platform wants to use DP for something else, I'm pretty much worried
> > that this is the right thing to do.
> 
> There is not much we can do about that. People can already model
> such displays as individual LEDs, too.
> And in some sense, the auxdisplay/linedisp driver for
> "generic-gpio-7seg" imposes a policy, too.

Does it? It's exactly targeting very specific HW configuration. The only
question here is DP.

> What if people want to e.g. use 4 7-seg displays to show a continuously
> running snake?

We have an ABI to update a "character" mapping, so it's possible to do, but
it is not a main purpose of line display library.

Free running 7-segment display does probably belong to LED framework in that
sense (as just represents a 7 LEDs that user configured in a specific way in
the physical world). In such case it's just the 7 LEDs on a single PCB.

If you consider these limits as "policy", okay, but it's _hardware driven_
one, and not software.

-- 
With Best Regards,
Andy Shevchenko