问题
I have some question about Linux kernel and GPIOs. I know that in Linux everything is file so when I do something like
echo 30 > /sys/class/gpio/export
and
echo 1 > /sys/class/gpio/gpio30/value
what really happens? I mean how does sysfs handle that? Does it call system calls implemented in gpiolib?
回答1:
The gpiolib registers the value attribute in this way:
static const DEVICE_ATTR(value, 0644, gpio_value_show, gpio_value_store);
It creates a device attribute named value, with permission 644; on read it calls gpio_value_show, on write it calls gpio_value_store
What sysfs does, is to redirect read and write to the correspondent function of a sysfs attribute.
来源：https://stackoverflow.com/questions/19548449/linux-gpios-handling