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Commit 14141a93 authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Linus Walleij
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gpio: simplify gpiochip_export() 



For some reason gpiochip_export() would invalidate all the descriptors
of a chip if exporting it to sysfs failed. This does not appear as
necessary. Remove that part of the code.

While we are at it, add a note about the non-safety of temporarily
releasing a spinlock in the middle of the loop that protects its
iterator, and explain why this is done.

Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent f63ad7ed

drivers/gpio/gpiolib-sysfs.c

+9 −11
Original line number Diff line number Diff line
@@ -760,18 +760,8 @@ int gpiochip_export(struct gpio_chip *chip) 
	chip->exported = (status == 0);

	mutex_unlock(&sysfs_lock);



	if (status) {

		unsigned long	flags;

		unsigned	gpio;



		spin_lock_irqsave(&gpio_lock, flags);

		gpio = 0;

		while (gpio < chip->ngpio)

			chip->desc[gpio++].chip = NULL;

		spin_unlock_irqrestore(&gpio_lock, flags);



	if (status)

		chip_dbg(chip, "%s: status %d\n", __func__, status);

	}



	return status;

}
@@ -817,6 +807,14 @@ static int __init gpiolib_sysfs_init(void) 
		if (!chip || chip->exported)

			continue;



		/*

		 * TODO we yield gpio_lock here because gpiochip_export()

		 * acquires a mutex. This is unsafe and needs to be fixed.

		 *

		 * Also it would be nice to use gpiochip_find() here so we

		 * can keep gpio_chips local to gpiolib.c, but the yield of

		 * gpio_lock prevents us from doing this.

		 */

		spin_unlock_irqrestore(&gpio_lock, flags);

		status = gpiochip_export(chip);

		spin_lock_irqsave(&gpio_lock, flags);