gpiolib: Refactor gpio_export

commit fc4e2514995d9cd7f3e1a67098ce65d72acf8ec7 upstream.

The gpio_export function uses nested if statements and the status
variable to handle the failure cases. This makes the function logic
difficult to follow. Refactor the code to abort immediately on failure
using goto. This makes the code slightly longer, but significantly
reduces the nesting and number of split lines and makes the code easier
to read.

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index c6df76245a2b84640c1fb8c9bb9cc01b2a811a8c..c579f3dace023e9a347ac0ce21951bf21d3d0f75 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -701,8 +701,9 @@ int gpio_export(unsigned gpio, bool direction_may_change)
 {
        unsigned long           flags;
        struct gpio_desc        *desc;
-       int                     status = -EINVAL;
+       int                     status;
        const char              *ioname = NULL;
+       struct device           *dev;
 
        /* can't export until sysfs is available ... */
        if (!gpio_class.p) {
@@ -710,59 +711,65 @@ int gpio_export(unsigned gpio, bool direction_may_change)
                return -ENOENT;
        }
 
-       if (!gpio_is_valid(gpio))
-               goto done;
+       if (!gpio_is_valid(gpio)) {
+               pr_debug("%s: gpio %d is not valid\n", __func__, gpio);
+               return -EINVAL;
+       }
 
        mutex_lock(&sysfs_lock);
 
        spin_lock_irqsave(&gpio_lock, flags);
        desc = &gpio_desc[gpio];
-       if (test_bit(FLAG_REQUESTED, &desc->flags)
-                       && !test_bit(FLAG_EXPORT, &desc->flags)) {
-               status = 0;
-               if (!desc->chip->direction_input
-                               || !desc->chip->direction_output)
-                       direction_may_change = false;
+       if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
+            test_bit(FLAG_EXPORT, &desc->flags)) {
+               spin_unlock_irqrestore(&gpio_lock, flags);
+               pr_debug("%s: gpio %d unavailable (requested=%d, exported=%d)\n",
+                               __func__, gpio,
+                               test_bit(FLAG_REQUESTED, &desc->flags),
+                               test_bit(FLAG_EXPORT, &desc->flags));
+               return -EPERM;
        }
+
+       if (!desc->chip->direction_input || !desc->chip->direction_output)
+               direction_may_change = false;
        spin_unlock_irqrestore(&gpio_lock, flags);
 
        if (desc->chip->names && desc->chip->names[gpio - desc->chip->base])
                ioname = desc->chip->names[gpio - desc->chip->base];
 
-       if (status == 0) {
-               struct device   *dev;
-
-               dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
-                               desc, ioname ? ioname : "gpio%u", gpio);
-               if (!IS_ERR(dev)) {
-                       status = sysfs_create_group(&dev->kobj,
-                                               &gpio_attr_group);
-
-                       if (!status && direction_may_change)
-                               status = device_create_file(dev,
-                                               &dev_attr_direction);
-
-                       if (!status && gpio_to_irq(gpio) >= 0
-                                       && (direction_may_change
-                                               || !test_bit(FLAG_IS_OUT,
-                                                       &desc->flags)))
-                               status = device_create_file(dev,
-                                               &dev_attr_edge);
-
-                       if (status != 0)
-                               device_unregister(dev);
-               } else
-                       status = PTR_ERR(dev);
-               if (status == 0)
-                       set_bit(FLAG_EXPORT, &desc->flags);
+       dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
+                           desc, ioname ? ioname : "gpio%u", gpio);
+       if (IS_ERR(dev)) {
+               status = PTR_ERR(dev);
+               goto fail_unlock;
        }
 
-       mutex_unlock(&sysfs_lock);
-
-done:
+       status = sysfs_create_group(&dev->kobj, &gpio_attr_group);
        if (status)
-               pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
+               goto fail_unregister_device;
+
+       if (direction_may_change) {
+               status = device_create_file(dev, &dev_attr_direction);
+               if (status)
+                       goto fail_unregister_device;
+       }
 
+       if (gpio_to_irq(gpio) >= 0 && (direction_may_change ||
+                                      !test_bit(FLAG_IS_OUT, &desc->flags))) {
+               status = device_create_file(dev, &dev_attr_edge);
+               if (status)
+                       goto fail_unregister_device;
+       }
+
+       set_bit(FLAG_EXPORT, &desc->flags);
+       mutex_unlock(&sysfs_lock);
+       return 0;
+
+fail_unregister_device:
+       device_unregister(dev);
+fail_unlock:
+       mutex_unlock(&sysfs_lock);
+       pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
        return status;
 }
 EXPORT_SYMBOL_GPL(gpio_export);