linux-kernel - [PATCH 3.4 107/176] gpiolib: Refactor gpio

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Message-Id: <1428569224-23820-107-git-send-email-lizf@kernel.org>
Date:	Thu,  9 Apr 2015 16:45:55 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Ryan Mallon <rmallon@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 107/176] gpiolib: Refactor gpio_export

From: Ryan Mallon <rmallon@...il.com>

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

------------------


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@...il.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 drivers/gpio/gpiolib.c | 85 +++++++++++++++++++++++++++-----------------------
 1 file changed, 46 insertions(+), 39 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index c6df762..c579f3d 100644
--- 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);
-- 
1.9.1

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