forked from Minki/linux
d8f388d8dc
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: David 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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| .. | ||
| boot | ||
| common | ||
| configs | ||
| kernel | ||
| lib | ||
| mach-aaec2000 | ||
| mach-at91 | ||
| mach-clps711x | ||
| mach-clps7500 | ||
| mach-davinci | ||
| mach-ebsa110 | ||
| mach-ep93xx | ||
| mach-footbridge | ||
| mach-h720x | ||
| mach-imx | ||
| mach-integrator | ||
| mach-iop13xx | ||
| mach-iop32x | ||
| mach-iop33x | ||
| mach-ixp4xx | ||
| mach-ixp23xx | ||
| mach-ixp2000 | ||
| mach-kirkwood | ||
| mach-ks8695 | ||
| mach-l7200 | ||
| mach-lh7a40x | ||
| mach-loki | ||
| mach-msm | ||
| mach-mv78xx0 | ||
| mach-mx2 | ||
| mach-mx3 | ||
| mach-netx | ||
| mach-ns9xxx | ||
| mach-omap1 | ||
| mach-omap2 | ||
| mach-orion5x | ||
| mach-pnx4008 | ||
| mach-pxa | ||
| mach-realview | ||
| mach-rpc | ||
| mach-s3c2400 | ||
| mach-s3c2410 | ||
| mach-s3c2412 | ||
| mach-s3c2440 | ||
| mach-s3c2442 | ||
| mach-s3c2443 | ||
| mach-sa1100 | ||
| mach-shark | ||
| mach-versatile | ||
| mm | ||
| nwfpe | ||
| oprofile | ||
| plat-iop | ||
| plat-mxc | ||
| plat-omap | ||
| plat-orion | ||
| plat-s3c | ||
| plat-s3c24xx | ||
| tools | ||
| vfp | ||
| Kconfig | ||
| Kconfig-nommu | ||
| Kconfig.debug | ||
| Makefile | ||