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gpio: simplify gpiochip_export()

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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>
This commit is contained in:
Alexandre Courbot 2014-07-22 16:17:40 +09:00 committed by Linus Walleij
parent f63ad7ed71
commit 14141a9352
1 changed files with 9 additions and 11 deletions
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20
drivers/gpio/gpiolib-sysfs.c
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@ -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);