Hi,
On 30.06.2010 04:09, Jon Povey wrote:
Nicolas Luna wrote:
Hi,
I wonder what would be the easiest way to control GPIO in userspace.
I read the documentation gpio.txt but I'm not sure what I should use
(Control interfaces?, GPIO controllers?) and how to implement it.
Is there more explication about int gpio_export_link(struct device
*dev, const char *name, unsigned gpio) because I think it could be
the key.
Will I need to write my own module and communicate with it?.
You don't need to write a module. You can access GPIOs from a shell script:
To be able to do so you must configure your kernel with the following
option enabled :
CONFIG_GPIO_SYSFS
echo $GPIO_NUMBER> /sys/class/gpio/export
creates a directory /sys/class/gpio/gpio$GPIO_NUMBER, e.g. 8.
(That will fail if something else like a driver has requested that gpio
already).
cat /sys/class/gpio/gpio8/value
gets the value 0/1
echo 1> /sys/class/gpio/gpio8/direction
sets it to output (iirc)
echo 1> /sys/class/gpio/gpio8/value
now sets the output value.
echo 8> /sys/class/gpio/unexport
to release it when you are finished.
gpio_export_link() is for when you claim a gpio for use in the kernel but also
want to export one of the above kind of sysfs entries.
--
Jon Povey
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