linux-kernel - Re: [PATCH] leds: leds-gpio: Convert gpio_blink

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Message-ID: <CAMuHMdUroLo5SdXrTu+etiW+TwHAWV-Qn9UsVnud+BJ7q6nXjw@mail.gmail.com>
Date:	Thu, 6 Nov 2014 12:12:04 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alexandre Courbot <acourbot@...dia.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Ben Dooks <ben-linux@...ff.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH] leds: leds-gpio: Convert gpio_blink_set() to use GPIO descriptors

Hi Mika,

On Thu, Nov 6, 2014 at 11:58 AM, Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
> On Thu, Nov 06, 2014 at 11:32:19AM +0100, Geert Uytterhoeven wrote:
>> On Thu, Nov 6, 2014 at 11:30 AM, Mika Westerberg
>> <mika.westerberg@...ux.intel.com> wrote:
>> >> "leds: leds-gpio: Add support for GPIO descriptors" broke leds-gpio on
>> >> non-DT platforms for me:
>> >>
>> >>     gpiod_direction_output: invalid GPIO
>> >>     leds-gpio: probe of leds-gpio failed with error -22
>> >>
>> >> (desc is NULL in gpiod_direction_output()).
>> >>
>> >> DT shmobile reference/multi-platform are fine.
>> >>
>> >> I noticed the hard way, as I wanted to add some LEDs to a new platform,
>> >> but couldn't get it work. It turned out it also had stopped working on
>> >> r8a7740/armadillo-legacy, so I started bisecting...
>> >
>> > Which board file that is?
>> >
>> > There is a bug that gpio_to_desc() returns NULL instead if ERR_PTR() in
>> > that patch but I wonder why gpio_is_valid() and devm_gpio_request_one()
>> > do not complain about that prior.
>>
>> arch/arm/mach-shmobile/board-armadillo800eva.c
>
> Are you able to put some printks() to the 'if (!template->gpiod)' branch
> so that it prints out gpio number and what does devm_gpio_request_one()
> return?
>
> Something like:
>
>         if (!template->gpiod) {
>                 ...
>                 ret = devm_gpio_request_one(parent, template->gpio, flags,
>                                             template->name);
>                 dev_info(parent, "GPIO %u, ret: %d\n", template->gpio, ret);
>                 if (ret < 0)
>                         ...
>
>                 led_dat->gpiod = gpio_to_desc(template->gpio);
>                 dev_info(parent, "GPIOD: %p\n", led_dat->gpiod);

Sure:

    leds-gpio leds-gpio: GPIO 102, ret: 0
    leds-gpio leds-gpio: GPIOD: c050e970

So led_dat is non-NULL. But it's overwritten by NULL later:

    led_dat->gpiod = template->gpiod;

Whitespace damaged fix below, to fold into the original.
If you prefer a proper separate patch, let me know.

diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
index ba4698c32bb04bde..b3c5d9d6a42bcd8b 100644
--- a/drivers/leds/leds-gpio.c
+++ b/drivers/leds/leds-gpio.c
@@ -92,7 +92,8 @@ static int create_gpio_led(const struct gpio_led *template,
 {
        int ret, state;

-       if (!template->gpiod) {
+       led_dat->gpiod = template->gpiod;
+       if (!led_dat->gpiod) {
                /*
                 * This is the legacy code path for platform code that
                 * still uses GPIO numbers. Ultimately we would like to get
@@ -122,8 +123,7 @@ static int create_gpio_led(const struct gpio_led *template,

        led_dat->cdev.name = template->name;
        led_dat->cdev.default_trigger = template->default_trigger;
-       led_dat->gpiod = template->gpiod;
-       led_dat->can_sleep = gpiod_cansleep(template->gpiod);
+       led_dat->can_sleep = gpiod_cansleep(led_dat->gpiod);
        led_dat->blinking = 0;
        if (blink_set) {
                led_dat->platform_gpio_blink_set = blink_set;

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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