Linux Device Drivers Development

Exporting a GPIO from kernel code

Apart from using the /sys/class/gpio/export file to export a GPIO to the user space, you can use functions such as gpio_export (for legacy interfaces) or gpioD_export (the new interface) from the kernel code in order to explicitly manage exporting the GPIOs that have already been requested using gpio_request() or gpiod_get():

int gpio_export(unsigned gpio, bool direction_may_change); 

int gpiod_export(struct gpio_desc *desc, bool direction_may_change); 

The direction_may_change parameter decides whether you can change the signal direction from input to output and vice versa. The reverse operations from the kernel are gpio_unexport() or gpiod_unexport():

void gpio_unexport(unsigned gpio); /* Integer-based interface ...