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  1. 09 10月, 2008 1 次提交
  3. 03 9月, 2008 1 次提交
  5. 07 8月, 2008 2 次提交
  7. 27 7月, 2008 1 次提交
  9. 26 7月, 2008 1 次提交
    • D
      gpio: sysfs interface · d8f388d8
      由 David Brownell 提交于 
      This adds a simple sysfs interface for GPIOs.

    /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
	    /value ... always readable, writes fail for input GPIOs
	    /direction ... r/w as: in, out (default low); write high, low
	/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 .. N+(ngpio - 1)

GPIOs claimed by kernel code may be exported by its owner using a new
gpio_export() call, which should be most useful for driver debugging.
Such exports may optionally be done without a "direction" attribute.

Userspace may ask to take over a GPIO by writing to a sysfs control file,
helping to cope with incomplete board support or other "one-off"
requirements that don't merit full kernel support:

  echo 23 > /sys/class/gpio/export
	... will gpio_request(23, "sysfs") and gpio_export(23);
	use /sys/class/gpio/gpio-23/direction to (re)configure it,
	when that GPIO can be used as both input and output.
  echo 23 > /sys/class/gpio/unexport
	... will gpio_free(23), when it was exported as above

The extra D-space footprint is a few hundred bytes, except for the sysfs
resources associated with each exported GPIO.  The additional I-space
footprint is about two thirds of the current size of gpiolib (!).  Since
no /dev node creation is involved, no "udev" support is needed.

Related changes:

  * This adds a device pointer to "struct gpio_chip".  When GPIO
    providers initialize that, sysfs gpio class devices become children of
    that device instead of being "virtual" devices.

  * The (few) gpio_chip providers which have such a device node have
    been updated.

  * Some gpio_chip drivers also needed to update their module "owner"
    field ...  for which missing kerneldoc was added.

  * Some gpio_chips don't support input GPIOs.  Those GPIOs are now
    flagged appropriately when the chip is registered.

Based on previous patches, and discussion both on and off LKML.

A Documentation/ABI/testing/sysfs-gpio update is ready to submit once this
merges to mainline.

[akpm@linux-foundation.org: a few maintenance build fixes]
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Cc: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d8f388d8
  11. 15 4月, 2008 3 次提交
  13. 20 3月, 2008 1 次提交
  15. 05 3月, 2008 2 次提交
  17. 09 2月, 2008 3 次提交
  19. 25 1月, 2008 1 次提交
  21. 20 10月, 2007 1 次提交
  23. 09 5月, 2007 1 次提交
  25. 05 5月, 2007 8 次提交
  27. 22 4月, 2007 1 次提交
  29. 02 3月, 2007 1 次提交
  31. 30 11月, 2006 1 次提交
  33. 07 10月, 2006 1 次提交
  35. 25 9月, 2006 7 次提交
  37. 02 8月, 2006 1 次提交
  39. 03 7月, 2006 1 次提交
  41. 02 7月, 2006 1 次提交