Linux Device Drivers Development

Sysfs interface for GPIO controller

On successful gpiochip_add(), a directory entry with a path such as /sys/class/gpio/gpiochipX/ will be created, where X is the GPIO controller base (the controller providing GPIOs starting at #X), with the following attributes:

• base, whose value is the same as X, and which corresponds to gpio_chip.base (if assigned statically) and is the first GPIO managed by this chip.
• label, which is provided for diagnostics (not always unique).
• ngpio, which tells how many GPIOs this controller provides (N to N + ngpio - 1). This is the same as defined in gpio_chip.ngpios.

All of the preceding attributes are read-only.