On named GPIOs there is currently no find out their numerical id.
Because of this, a GPIO pin named like:
/sys/class/gpio/PROG_B
cannot be unexported by an application different than the one that
exported it.
This patch adds a new parameter to the GPIO line called id, that
shows the numerical id of a given GPIO. E.g.:
$ cat /sys/class/gpio/PROG_B/id
496
$ echo 496 > unexport
Signed-off-by: Ricardo Ribalda Delgado <ricardo.riba...@gmail.com>
---
Documentation/ABI/testing/sysfs-gpio | 1 +
Documentation/gpio/sysfs.txt | 3 +++
drivers/gpio/gpiolib-sysfs.c | 10 ++++++++++
3 files changed, 14 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-gpio
b/Documentation/ABI/testing/sysfs-gpio
index 55ffa2df1c10..53d78abef4f3 100644
--- a/Documentation/ABI/testing/sysfs-gpio
+++ b/Documentation/ABI/testing/sysfs-gpio
@@ -21,6 +21,7 @@ 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
+ /id ... r only, GPIO number
/gpiochipN ... for each gpiochip; #N is its first GPIO
/base ... (r/o) same as N
/label ... (r/o) descriptive, not necessarily unique
diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt
index aeab01aa4d00..68e1b16e747b 100644
--- a/Documentation/gpio/sysfs.txt
+++ b/Documentation/gpio/sysfs.txt
@@ -96,6 +96,9 @@ and have the following read/write attributes:
for "rising" and "falling" edges will follow this
setting.
+ "id" ... ID used for export/unxexport the GPIO. This value may
+ be used by named GPIOs, to find out their numerical id.
+
GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
controller implementing GPIOs starting at #42) and have the following
read-only attributes:
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index b57ed8e55ab5..3fc5c7231aae 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -350,6 +350,15 @@ static ssize_t active_low_store(struct device *dev,
}
static DEVICE_ATTR_RW(active_low);
+static ssize_t id_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct gpiod_data *data = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%d\n", desc_to_gpio(data->desc));
+}
+static DEVICE_ATTR_RO(id);
+
static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
int n)
{
@@ -377,6 +386,7 @@ static struct attribute *gpio_attrs[] = {
&dev_attr_edge.attr,
&dev_attr_value.attr,
&dev_attr_active_low.attr,
+ &dev_attr_id.attr,
NULL,
};
--
2.6.4
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