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Date:   Fri, 24 Sep 2021 03:49:01 +0000
From:   Joel Stanley <>
To:     Andrew Jeffery <>
        "open list:GPIO SUBSYSTEM" <>,
        C├ędric Le Goater <>,
        Rob Herring <>, Pavel Machek <>,
        Linus Walleij <>,
        devicetree <>,
        Linux ARM <>,
        linux-aspeed <>,
        Linux Kernel Mailing List <>,
        Andy Shevchenko <>
Subject: Re: [PATCH 0/2] leds: pca955x: Expose GPIOs for all pins

On Tue, 21 Sept 2021 at 04:39, Andrew Jeffery <> wrote:
> Hello,
> This is a rework of a Rube Goldberg-inspired RFC I posted previously:
> This time around there's a lot less Rube - the series:
> 1. Contains no (ab)use of pinctrl
> 2. Always exposes all pins as GPIOs
> 3. Internally tracks the active pins
> 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!

Reviewed-by: Joel Stanley <>



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