linux-kernel - Re: [PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

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Date: Tue, 13 Feb 2024 16:42:53 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Kent Gibson <warthog618@...il.com>, Alex Elder <elder@...aro.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Wolfram Sang <wsa@...-dreams.de>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] gpio: initialize descriptor SRCU structure before adding
 OF-based chips

On Mon, Feb 12, 2024 at 10:39:20PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> In certain situations we may end up taking the GPIO descriptor SRCU read
> lock in of_gpiochip_add() before the SRCU struct is initialized. Move
> the initialization before the call to of_gpiochip_add().

..

This is a bit unclear why you moved to that place and how it had been tested.

> @@ -991,10 +991,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>  	if (ret)
>  		goto err_cleanup_gdev_srcu;
>  
> -	ret = of_gpiochip_add(gc);
> -	if (ret)
> -		goto err_free_gpiochip_mask;
> -
>  	for (i = 0; i < gc->ngpio; i++) {
>  		struct gpio_desc *desc = &gdev->descs[i];
>  

>  		if (ret) {
>  			for (j = 0; j < i; j++)
>  				cleanup_srcu_struct(&gdev->descs[j].srcu);
> -			goto err_remove_of_chip;
> +			goto err_free_gpiochip_mask;
>  		}
>  
>  		if (gc->get_direction && gpiochip_line_is_valid(gc, i)) {

>  		}
>  	}
>  
> -	ret = gpiochip_add_pin_ranges(gc);
> +	ret = of_gpiochip_add(gc);
>  	if (ret)
>  		goto err_cleanup_desc_srcu;
>  
> +	ret = gpiochip_add_pin_ranges(gc);
> +	if (ret)
> +		goto err_remove_of_chip;
> +
>  	acpi_gpiochip_add(gc);

My logic tells me that if you need to call gpiochip_add_pin_ranges() before
calling of_gpiochip_add(). It won't collide right now, but allows to cleanup
further (with the gpio-ranges parser be generalized for fwnodes and be moved
to gpiolib.c from gpiolib-of.c).

-- 
With Best Regards,
Andy Shevchenko