by Roland Stigge

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Subject: [PATCH 4/6 v8] gpiolib: Fix default attributes for class

There is a race condition between creating a gpio or gpiochip device and adding
default attributes. This patch fixes this by defining the default attributes as
dev_attrs of the class. For this, it was necessary to create a separate
gpiochip_class besides gpio_class.

Signed-off-by: Roland Stigge <[email protected]>
---
Documentation/ABI/testing/sysfs-gpio | 11 ++++
drivers/gpio/gpiolib.c | 79 +++++++++++++++--------------------
2 files changed, 45 insertions(+), 45 deletions(-)

--- linux-2.6.orig/Documentation/ABI/testing/sysfs-gpio
+++ linux-2.6/Documentation/ABI/testing/sysfs-gpio
@@ -20,6 +20,17 @@ Description:
/value ... always readable, writes fail for input GPIOs
/direction ... r/w as: in, out (default low); write: high, low
/edge ... r/w as: none, falling, rising, both
+
+What: /sys/class/gpiochip/
+Date: October 2012
+KernelVersion: 3.7
+Contact: Roland Stigge <[email protected]>
+Description:
+
+ Each gpiochip is represented by a separate device having the following
+ attributes:
+
+ /sys/class/gpiochip
/gpiochipN ... for each gpiochip; #N is its first GPIO
/base ... (r/o) same as N
/label ... (r/o) descriptive, not necessarily unique
--- linux-2.6.orig/drivers/gpio/gpiolib.c
+++ linux-2.6/drivers/gpio/gpiolib.c
@@ -333,9 +333,6 @@ static ssize_t gpio_value_store(struct d
return status;
}

-static const DEVICE_ATTR(value, 0644,
- gpio_value_show, gpio_value_store);
-
static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
{
struct sysfs_dirent *value_sd = priv;
@@ -556,19 +553,6 @@ static ssize_t gpio_active_low_store(str
return status ? : size;
}

-static const DEVICE_ATTR(active_low, 0644,
- gpio_active_low_show, gpio_active_low_store);
-
-static const struct attribute *gpio_attrs[] = {
- &dev_attr_value.attr,
- &dev_attr_active_low.attr,
- NULL,
-};
-
-static const struct attribute_group gpio_attr_group = {
- .attrs = (struct attribute **) gpio_attrs,
-};
-
/*
* /sys/class/gpio/gpiochipN/
* /base ... matching gpio_chip.base (N)
@@ -583,7 +567,6 @@ static ssize_t chip_base_show(struct dev

return sprintf(buf, "%d\n", chip->base);
}
-static DEVICE_ATTR(base, 0444, chip_base_show, NULL);

static ssize_t chip_label_show(struct device *dev,
struct device_attribute *attr, char *buf)
@@ -592,7 +575,6 @@ static ssize_t chip_label_show(struct de

return sprintf(buf, "%s\n", chip->label ? : "");
}
-static DEVICE_ATTR(label, 0444, chip_label_show, NULL);

static ssize_t chip_ngpio_show(struct device *dev,
struct device_attribute *attr, char *buf)
@@ -601,18 +583,6 @@ static ssize_t chip_ngpio_show(struct de

return sprintf(buf, "%u\n", chip->ngpio);
}
-static DEVICE_ATTR(ngpio, 0444, chip_ngpio_show, NULL);
-
-static const struct attribute *gpiochip_attrs[] = {
- &dev_attr_base.attr,
- &dev_attr_label.attr,
- &dev_attr_ngpio.attr,
- NULL,
-};
-
-static const struct attribute_group gpiochip_attr_group = {
- .attrs = (struct attribute **) gpiochip_attrs,
-};

/*
* /sys/class/gpio/export ... write-only
@@ -691,11 +661,32 @@ static struct class_attribute gpio_class
__ATTR_NULL,
};

+static struct device_attribute gpio_attrs[] = {
+ __ATTR(active_low, 0644, gpio_active_low_show, gpio_active_low_store),
+ __ATTR(value, 0644, gpio_value_show, gpio_value_store),
+ __ATTR_NULL,
+};
+
static struct class gpio_class = {
.name = "gpio",
.owner = THIS_MODULE,

- .class_attrs = gpio_class_attrs,
+ .class_attrs = gpio_class_attrs,
+ .dev_attrs = gpio_attrs,
+};
+
+static struct device_attribute gpiochip_attrs[] = {
+ __ATTR(label, 0444, chip_label_show, NULL),
+ __ATTR(base, 0444, chip_base_show, NULL),
+ __ATTR(ngpio, 0444, chip_ngpio_show, NULL),
+ __ATTR_NULL,
+};
+
+static struct class gpiochip_class = {
+ .name = "gpiochip",
+ .owner = THIS_MODULE,
+
+ .dev_attrs = gpiochip_attrs,
};

@@ -752,10 +743,7 @@ int gpio_export(unsigned gpio, bool dire
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)
+ if (direction_may_change)
status = device_create_file(dev,
&dev_attr_direction);

@@ -925,25 +913,22 @@ EXPORT_SYMBOL_GPL(gpio_unexport);

static int gpiochip_export(struct gpio_chip *chip)
{
- int status;
+ int status = 0;
struct device *dev;

/* Many systems register gpio chips for SOC support very early,
* before driver model support is available. In those cases we
* export this later, in gpiolib_sysfs_init() ... here we just
- * verify that _some_ field of gpio_class got initialized.
+ * verify that _some_ field of gpiochip_class got initialized.
*/
- if (!gpio_class.p)
+ if (!gpiochip_class.p)
return 0;

/* use chip->base for the ID; it's already known to be unique */
mutex_lock(&sysfs_lock);
- dev = device_create(&gpio_class, chip->dev, MKDEV(0, 0), chip,
- "gpiochip%d", chip->base);
- if (!IS_ERR(dev)) {
- status = sysfs_create_group(&dev->kobj,
- &gpiochip_attr_group);
- } else
+ dev = device_create(&gpiochip_class, chip->dev, MKDEV(0, 0), chip,
+ "gpiochip%d", chip->base);
+ if (IS_ERR(dev))
status = PTR_ERR(dev);
chip->exported = (status == 0);
mutex_unlock(&sysfs_lock);
@@ -971,7 +956,7 @@ static void gpiochip_unexport(struct gpi
struct device *dev;

mutex_lock(&sysfs_lock);
- dev = class_find_device(&gpio_class, NULL, chip, match_export);
+ dev = class_find_device(&gpiochip_class, NULL, chip, match_export);
if (dev) {
put_device(dev);
device_unregister(dev);
@@ -1228,6 +1213,10 @@ static int __init gpiolib_sysfs_init(voi
if (status < 0)
return status;

+ status = class_register(&gpiochip_class);
+ if (status < 0)
+ return status;
+
status = class_register(&gpio_block_class);
if (status < 0)
return status;