gpiolib: allow exported GPIO nodes to be named using sysfs links

Commit 926b663ce8215ba448960e1ff6e58b67a2c3b99b (gpiolib: allow GPIOs to
be named) already provides naming on the chip level. This patch provides
more flexibility by allowing multiple names where ever in sysfs on a per
GPIO basis.

Adapted from David Brownell's comments on a similar concept:
http://lkml.org/lkml/2009/4/20/203.

[randy.dunlap@oracle.com: fix build for CONFIG_GENERIC_GPIO=n]
Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Acked-by: David Brownell <david-b@pacbell.net>
Cc: Daniel Silverstone <dsilvers@simtec.co.uk>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 19 insertions, 0 deletions

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index d6c379dc64fa..9cca3785cab8 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -141,6 +141,8 @@ extern int __gpio_to_irq(unsigned gpio);
  * but more typically is configured entirely from userspace.
  */
 extern int gpio_export(unsigned gpio, bool direction_may_change);
+extern int gpio_export_link(struct device *dev, const char *name,
+                        unsigned gpio);
 extern void gpio_unexport(unsigned gpio);
 
 #endif  /* CONFIG_GPIO_SYSFS */
@@ -185,6 +187,12 @@ static inline int gpio_export(unsigned gpio, bool direction_may_change)
         return -ENOSYS;
 }
 
+static inline int gpio_export_link(struct device *dev, const char *name,
+                                unsigned gpio)
+{
+        return -ENOSYS;
+}
+
 static inline void gpio_unexport(unsigned gpio)
 {
 }
diff --git a/include/linux/gpio.h b/include/linux/gpio.h
index e10c49a5b96e..059bd189d35d 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -12,6 +12,8 @@
 #include <linux/types.h>
 #include <linux/errno.h>
 
+struct device;
+
 /*
  * Some platforms don't support the GPIO programming interface.
  *
@@ -89,6 +91,15 @@ static inline int gpio_export(unsigned gpio, bool direction_may_change)
         return -EINVAL;
 }
 
+static inline int gpio_export_link(struct device *dev, const char *name,
+                                unsigned gpio)
+{
+        /* GPIO can never have been exported */
+        WARN_ON(1);
+        return -EINVAL;
+}
+
+
 static inline void gpio_unexport(unsigned gpio)
 {
         /* GPIO can never have been exported */