gpiolib: add support for changing value polarity in sysfs

Drivers may use gpiolib sysfs as part of their public user space
interface. The GPIO number and polarity might change from board to
board. The gpio_export_link() call can be used to hide the GPIO number
from user space. Add support for also hiding the GPIO line polarity
changes from user space.

Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 204bed37e82d..485eeb6c4ef3 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -145,6 +145,7 @@ extern int __gpio_to_irq(unsigned gpio);
 extern int gpio_export(unsigned gpio, bool direction_may_change);
 extern int gpio_export_link(struct device *dev, const char *name,
                         unsigned gpio);
+extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
 extern void gpio_unexport(unsigned gpio);
 
 #endif  /* CONFIG_GPIO_SYSFS */
@@ -197,6 +198,11 @@ static inline int gpio_export_link(struct device *dev, const char *name,
         return -ENOSYS;
 }
 
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+        return -ENOSYS;
+}
+
 static inline void gpio_unexport(unsigned gpio)
 {
 }