linux-kernel - Re: [PATCH 0/2] leds: pca955x: Expose GPIOs for all pins

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Date:   Mon, 21 Feb 2022 07:33:59 +0000
From:   Joel Stanley <joel@....id.au>
To:     Pavel Machek <pavel@....cz>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Cédric Le Goater <clg@...d.org>,
        linux-leds@...r.kernel.org,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH 0/2] leds: pca955x: Expose GPIOs for all pins

Hello Pavel,



On Fri, 24 Sept 2021 at 06:41, Cédric Le Goater <clg@...d.org> wrote:
>
> On 9/21/21 06:39, Andrew Jeffery wrote:
> > Without these patches the driver limits the number of pins exposed on
> > the gpiochip to the number of pins specified as GPIO in the devicetree,
> > but doesn't map between the GPIO and pin number spaces. The result is
> > that specifying offset or interleaved GPIOs in the devicetree gives
> > unexpected behaviour in userspace.
> >
> > By always exposing all pins as GPIOs the patches resolve the lack of
> > mapping between GPIO offsets and pins on the package in the driver by
> > ensuring we always have a 1-to-1 mapping.
> >
> > The issue is primarily addressed by patch 1/2. Patch 2/2 makes it
> > possible to not expose any pins as LEDs (and therefore make them all
> > accessible as GPIOs). This has a follow-on effect of allowing the driver
> > to bind to a device instantiated at runtime without requiring a
> > description in the devicetree.
> >
> > I've tested the series under qemu to inspect the various interactions
> > between LEDs vs GPIOs as well as conflicting GPIO requests.

> > Please review!
>
> This is simpler than the 'ngpio' business we had before.
>
> Reviewed-by: Cédric Le Goater <clg@...d.org>

I saw that you recently merged some LED patches. I was wondering if
you could consider this series for v5.18. It still applies cleanly,
and we've been running it for a while now, so it's very well tested.

Cheers,

Joel