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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-16 10:06:39 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-16 10:06:39 -0800 |
| commit | 9cfc86249f32d984339c6d1f8a1fd1326989b3b8 (patch) | |
| tree | 56428d319483f54949de8d9d0a5b3f715287ed91 /Documentation/gpio.txt | |
| parent | f42647acc4eab1befa9e290691ed7a40f9a7d3cc (diff) | |
| parent | 243797f59b748f679ab88d456fcc4f92236d724b (diff) | |
Merge branch 'akpm'
* akpm: (173 commits)
genalloc: use bitmap_find_next_zero_area
ia64: use bitmap_find_next_zero_area
sparc: use bitmap_find_next_zero_area
mlx4: use bitmap_find_next_zero_area
isp1362-hcd: use bitmap_find_next_zero_area
iommu-helper: use bitmap library
bitmap: introduce bitmap_set, bitmap_clear, bitmap_find_next_zero_area
qnx4: use hweight8
qnx4fs: remove remains of the (defunct) write support
resource: constify arg to resource_size() and resource_type()
gru: send cross partition interrupts using the gru
gru: function to generate chipset IPI values
gru: update driver version number
gru: improve GRU TLB dropin statistics
gru: fix GRU interrupt race at deallocate
gru: add hugepage support
gru: fix bug in allocation of kernel contexts
gru: update GRU structures to match latest hardware spec
gru: check for correct GRU chiplet assignment
gru: remove stray local_irq_enable
...
Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index e4e7daed2ba..1866c27eec6 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -531,6 +531,13 @@ and have the following read/write attributes: This file exists only if the pin can be configured as an interrupt generating input pin. + "active_low" ... reads as either 0 (false) or 1 (true). Write + any nonzero value to invert the value attribute both + for reading and writing. Existing and subsequent + poll(2) support configuration via the edge attribute + for "rising" and "falling" edges will follow this + setting. + GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the controller implementing GPIOs starting at #42) and have the following read-only attributes: @@ -566,6 +573,8 @@ requested using gpio_request(): int gpio_export_link(struct device *dev, const char *name, unsigned gpio) + /* change the polarity of a GPIO node in sysfs */ + int gpio_sysfs_set_active_low(unsigned gpio, int value); 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 @@ -580,3 +589,9 @@ 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. + +Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity +differences between boards from user space. This only affects the +sysfs interface. Polarity change can be done both before and after +gpio_export(), and previously enabled poll(2) support for either +rising or falling edge will be reconfigured to follow this setting. |