gpio: simplify gpiochip_export() (14141a93) · Commits · 戴 / test

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:

Alexandre Courbot <acourbot@nvidia.com> Signed-off-by:

Linus Walleij <linus.walleij@linaro.org>

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);

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