linux-kernel - Re: [PATCH v2] leds: simatic-ipc-leds-gpio: make sure we have the GPIO providing driver

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Date:   Wed, 24 Aug 2022 15:16:43 +0200
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        <linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] leds: simatic-ipc-leds-gpio: make sure we have the
 GPIO providing driver

Sending again to make sure it is not missed, also i included a "Fixes"
into the commit message. Tested on recent master, still applies.

regards,
Henning

Am Wed, 24 Aug 2022 15:14:28 +0200
schrieb Henning Schild <henning.schild@...mens.com>:

> If we register a "leds-gpio" platform device for GPIO pins that do not
> exist we get a -EPROBE_DEFER and the probe will be tried again later.
> If there is not driver to provide that pin we will poll forever and
> also create a lot of log messages.
> 
> So check if that GPIO driver is configured, if so it will come up
> eventually. If not we exit our probe function early and do not even
> bother registering the "leds-gpio". This method was chosen over
> "Kconfig depends" since this way we can add support for more devices
> and GPIO backends more easily without "depends"ing on all GPIO
> backends.
> 
> Fixes: a6c80bec3c93 ("leds: simatic-ipc-leds-gpio: Add GPIO version
> of Siemens driver") Signed-off-by: Henning Schild
> <henning.schild@...mens.com> ---
>  drivers/leds/simple/simatic-ipc-leds-gpio.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/leds/simple/simatic-ipc-leds-gpio.c
> b/drivers/leds/simple/simatic-ipc-leds-gpio.c index
> 4c9e663a90ba..0c96ba98e338 100644 ---
> a/drivers/leds/simple/simatic-ipc-leds-gpio.c +++
> b/drivers/leds/simple/simatic-ipc-leds-gpio.c @@ -57,6 +57,8 @@
> static int simatic_ipc_leds_gpio_probe(struct platform_device *pdev)
> struct gpio_desc *gpiod; int err;
>  
> +	if (!IS_ENABLED(CONFIG_PINCTRL_BROXTON))
> +		return -ENODEV;
>  	gpiod_add_lookup_table(&simatic_ipc_led_gpio_table);
>  	simatic_leds_pdev = platform_device_register_resndata(NULL,
>  		"leds-gpio", PLATFORM_DEVID_NONE, NULL, 0,