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

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Message-ID: <20220302085432.GA11054@duo.ucw.cz>
Date:   Wed, 2 Mar 2022 09:54:32 +0100
From:   Pavel Machek <pavel@....cz>
To:     Joel Stanley <joel@....id.au>
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

Hi!

> > > 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.

Thanks, applied. I must say this is really ninja-mutant driver, but I
see no better way.

+++ b/drivers/leds/leds-pca955x.c
@@ -429,7 +429,7 @@ pca955x_get_pdata(struct i2c_client *client, struct pca955x_chipdef *chip)
        int count;

This really should be unsigned. Care to fix/submit a patch?

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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