[mirror_ubuntu-zesty-kernel.git] / Documentation / ABI / obsolete / sysfs-gpio

What:		/sys/class/gpio/
Date:		July 2008
KernelVersion:	2.6.27
Contact:	Linus Walleij <linusw@kernel.org>
Description:

  As a Kconfig option, individual GPIO signals may be accessed from
  userspace.  GPIOs are only made available to userspace by an explicit
  "export" operation.  If a given GPIO is not claimed for use by
  kernel code, it may be exported by userspace (and unexported later).
  Kernel code may export it for complete or partial access.

  GPIOs are identified as they are inside the kernel, using integers in
  the range 0..INT_MAX.  See Documentation/gpio.txt for more information.

    /sys/class/gpio
	/export ... asks the kernel to export a GPIO to userspace
	/unexport ... to return a GPIO to the kernel
	/gpioN ... for each exported GPIO #N OR
	/<LINE-NAME> ... for a properly named GPIO line
	    /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
	/gpiochipN ... for each gpiochip; #N is its first GPIO
	    /base ... (r/o) same as N
	    /label ... (r/o) descriptive, not necessarily unique
	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)

  This ABI is deprecated and will be removed after 2020. It is
  replaced with the GPIO character device.
Commit	Line	Data
9f986a8c DB	1	What: /sys/class/gpio/
	2	Date: July 2008
	3	KernelVersion: 2.6.27
fe95046e	4	Contact: Linus Walleij <linusw@kernel.org>
9f986a8c DB	5	Description:
	6
	7	As a Kconfig option, individual GPIO signals may be accessed from
	8	userspace. GPIOs are only made available to userspace by an explicit
	9	"export" operation. If a given GPIO is not claimed for use by
	10	kernel code, it may be exported by userspace (and unexported later).
	11	Kernel code may export it for complete or partial access.
	12
	13	GPIOs are identified as they are inside the kernel, using integers in
	14	the range 0..INT_MAX. See Documentation/gpio.txt for more information.
	15
	16	/sys/class/gpio
	17	/export ... asks the kernel to export a GPIO to userspace
	18	/unexport ... to return a GPIO to the kernel
77a775b7 LW	19	/gpioN ... for each exported GPIO #N OR
77a775b7 LW	20	/<LINE-NAME> ... for a properly named GPIO line
9f986a8c DB	21	/value ... always readable, writes fail for input GPIOs
9f986a8c DB	22	/direction ... r/w as: in, out (default low); write: high, low
ff77c352	23	/edge ... r/w as: none, falling, rising, both
9f986a8c DB	24	/gpiochipN ... for each gpiochip; #N is its first GPIO
	25	/base ... (r/o) same as N
	26	/label ... (r/o) descriptive, not necessarily unique
	27	/ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
	28
fe95046e LW	29	This ABI is deprecated and will be removed after 2020. It is
fe95046e LW	30	replaced with the GPIO character device.