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/linux/gpio.h b/include/linux/gpio.h
index 059bd189d35d..4e949a5b5b85 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -99,6 +99,12 @@ static inline int gpio_export_link(struct device *dev, const char *name,
         return -EINVAL;
 }
 
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+        /* GPIO can never have been requested */
+        WARN_ON(1);
+        return -EINVAL;
+}
 
 static inline void gpio_unexport(unsigned gpio)
 {