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author | Haavard Skinnemoen <haavard.skinnemoen@atmel.com> | 2009-10-06 17:36:55 +0200 |
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committer | Haavard Skinnemoen <haavard.skinnemoen@atmel.com> | 2009-10-06 17:36:55 +0200 |
commit | d94e5fcbf1420366dcb4102bafe04dbcfc0d0d4b (patch) | |
tree | a9b7de7df6da5c3132cc68169b9c47ba288ccd42 /Documentation/gpio.txt | |
parent | avr32: MRMT: correct setup of SPI slaves (diff) | |
parent | Linux 2.6.32-rc3 (diff) | |
download | linux-d94e5fcbf1420366dcb4102bafe04dbcfc0d0d4b.tar.xz linux-d94e5fcbf1420366dcb4102bafe04dbcfc0d0d4b.zip |
Merge commit 'v2.6.32-rc3'
Diffstat (limited to 'Documentation/gpio.txt')
-rw-r--r-- | Documentation/gpio.txt | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index e4b6985044a2..fa4dc077ae0e 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -524,6 +524,13 @@ and have the following read/write attributes: is configured as an output, this value may be written; any nonzero value is treated as high. + "edge" ... reads as either "none", "rising", "falling", or + "both". Write these strings to select the signal edge(s) + that will make poll(2) on the "value" file return. + + This file exists only if the pin can be configured as an + interrupt generating input pin. + GPIO controllers have paths like /sys/class/gpio/chipchip42/ (for the controller implementing GPIOs starting at #42) and have the following read-only attributes: @@ -555,6 +562,11 @@ requested using gpio_request(): /* reverse gpio_export() */ void gpio_unexport(); + /* create a sysfs link to an exported GPIO node */ + int gpio_export_link(struct device *dev, const char *name, + unsigned gpio) + + After a kernel driver requests a GPIO, it may only be made available in the sysfs interface by gpio_export(). The driver can control whether the signal direction may change. This helps drivers prevent userspace code @@ -563,3 +575,8 @@ from accidentally clobbering important system state. This explicit exporting can help with debugging (by making some kinds of experiments easier), or can provide an always-there interface that's suitable for documenting as part of a board support package. + +After the GPIO has been exported, gpio_export_link() allows creating +symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can +use this to provide the interface under their own device in sysfs with +a descriptive name. |