[PATCH] GPIO core

This defines a simple and minimalist programming interface for GPIO APIs:

  - Documentation/gpio.txt ... describes things (read it)

  - include/asm-arm/gpio.h ... defines the ARM hook, which just punts
    to <asm/arch/gpio.h> for any implementation

  - include/asm-generic/gpio.h ... implement "can sleep" variants as calling
    the normal ones, for systems that don't handle i2c expanders.

The immediate need for such a cross-architecture API convention is to support
drivers that work the same on AT91 ARM and AVR32 AP7000 chips, which embed many
of the same controllers but have different CPUs.  However, several other users
have been reported, including a driver for a hardware watchdog chip and some
handhelds.org multi-CPU button drivers.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-arm/gpio.h

+#ifndef _ARCH_ARM_GPIO_H
+#define _ARCH_ARM_GPIO_H
+
+/* not all ARM platforms necessarily support this API ... */
+#include <asm/arch/gpio.h>
+
+#endif /* _ARCH_ARM_GPIO_H */

include/asm-generic/gpio.h

+#ifndef _ASM_GENERIC_GPIO_H
+#define _ASM_GENERIC_GPIO_H
+
+/* platforms that don't directly support access to GPIOs through I2C, SPI,
+ * or other blocking infrastructure can use these wrappers.
+ */
+
+static inline int gpio_cansleep(unsigned gpio)
+{
+	return 0;
+}
+
+static inline int gpio_get_value_cansleep(unsigned gpio)
+{
+	might_sleep();
+	return gpio_get_value(gpio);
+}
+
+static inline void gpio_set_value_cansleep(unsigned gpio, int value)
+{
+	might_sleep();
+	gpio_set_value(gpio, value);
+}
+
+#endif /* _ASM_GENERIC_GPIO_H */