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authorAlexandre Courbot <acourbot@nvidia.com>2014-07-22 11:17:40 +0400
committerLinus Walleij <linus.walleij@linaro.org>2014-07-23 19:37:51 +0400
commit14141a9352d007434ff61df1e16a2bcaf3119307 (patch)
treef54c02c3344952004a08f1ea3f1913467c5fa357 /drivers/gpio
parentf63ad7ed71e525b74fe486d25cdc788d6531f4a9 (diff)
downloadlinux-14141a9352d007434ff61df1e16a2bcaf3119307.tar.xz
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: Alexandre Courbot <acourbot@nvidia.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/gpio')
-rw-r--r--drivers/gpio/gpiolib-sysfs.c20
1 files changed, 9 insertions, 11 deletions
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 3516502059f2..f150aa288fa1 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -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);