linux-kernel - Re: about pca955x led driver gpio management

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Date:   Tue, 17 Oct 2017 10:18:10 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Andrea Scian - DAVE Embedded Systems <andrea.scian@...e.eu>
Cc:     Bryan Wu <cooloney@...il.com>, Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <j.anaszewski@...sung.com>,
        linux-leds@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: about pca955x led driver gpio management

On 10/17/2017 09:36 AM, Andrea Scian - DAVE Embedded Systems wrote:
> Dear all,
> 
> I'm working on an iMX6 based board with a PCA9555 which is used both to drive LEDs and manage some GPIOs.

The PCA9555 chip and the PCA955[0-3] chips have different control 
registers. You need a different led driver for it.

C.  

> My current kernel is quite old (4.1.15) but I've found Cédric patches on mainline and backported to this old revision.
> 
> I'm facing an issue with it, because it seems that it fails when it's used in a mixed (led/gpios) environment.
> 
> E.g.: let's say that I have one led connected to LED0 output and one GPIO connected at LED1 output.
> 
> I define it as
> 
>                         pca9551: pca9551@60 {
>                                 compatible = "nxp,pca9551";
>                                 reg = <0x60>;
>                                 #address-cells = <1>;
>                                 #size-cells = <0>;
>                                 #gpio-cells = <1>;
> 
>                                 led@0 {
>                                         label = "led0";
>                                         reg = <0>;
>                                         linux,default-trigger = "none";
>                                 };
>                                 gpio@1 {
>                                         label = "gpio1";
>                                         reg = <1>;
>                                         type = <2>; /* GPIO */
>                                 };
>                 };
> 
> At boot it's probed as
> 
> root@...-lynx:~# dmesg | grep pca
> [    5.315425] leds-pca955x 5-0060: leds-pca955x: Using pca9551 8-bit LED driver at slave address 0x60
> [    5.350349] leds-pca955x 5-0060: gpios 511...511
> 
> But I cannot access it:
> 
> root@...-lynx:~# echo 511 > /sys/class/gpio/export
> -sh: echo: write error: Device or resource busy
> 
> Because for pca955x_gpio_request_pin() this is at offset 0 (in fact is the first gpio registered of this gpio_chip) but it's the index 1 inside pca955x->leds[]
> 
> Am I missing something? (maybe I made a mistake in my backport and/or I'm missing some patches about the GPIO subsystems).
> 
> If I'm right I think I can send a patch to fix this (I'm thinking about having an array of GPIO index to map offset -> pca955x->leds[] index or just register all pins as GPIOs and then just report the busy state)
> 
> WDYT?
> 
> Kind Regards,
>