Documentation/ABI/obsolete/sysfs-gpio

Source file repositories/reference/linux-study-clean/Documentation/ABI/obsolete/sysfs-gpio

File Facts

System: Linux kernel
Corpus path: Documentation/ABI/obsolete/sysfs-gpio
Extension: [no extension]
Size: 1753 bytes
Lines: 41
Domain: Support Tooling And Documentation
Bucket: Documentation
Inferred role: Support Tooling And Documentation: Documentation
Status: atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

No C-style include directives detected by the generator.

Detected Declarations

No top-level syscall, struct, function, initcall, or export declaration detected by the generator.

Annotated Snippet

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/admin-guide/gpio 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
	    /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
	    /active_low ... r/w as: 0, 1
	/gpiochipN ... for each gpiochip; #N is its first GPIO
	    /base ... (r/o) same as N
	    /label ... (r/o) descriptive chip name
	    /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
	    /gpio<OFFSET>
	        /value ... always readable, writes fail for input GPIOs
	        /direction ... r/w as: in, out (default low); write: high, low
	/chipX ... for each gpiochip; #X is the gpio device ID
	    /export ... asks the kernel to export a GPIO at HW offset X to userspace
	    /unexport ... to return a GPIO at HW offset X to the kernel
	    /label ... (r/o) descriptive chip name
	    /ngpio ... (r/o) number of GPIOs exposed by the chip

  This ABI is obsoleted by Documentation/ABI/testing/gpio-cdev and will be
  removed after 2020.

Annotation

Atlas domain: Support Tooling And Documentation / Documentation.
Implementation status: atlas-only.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.