gpio: <linux/gpio.h> and "no GPIO support here" stubs

Add a <linux/gpio.h> defining fail/warn stubs for GPIO calls on platforms that
don't support the GPIO programming interface.  That includes the arch-specific
implementation glue otherwise.

This facilitates a new model for GPIO usage: drivers that can use GPIOs if
they're available, but don't require them.  One example of such a driver is
NAND driver for various FreeScale chips.  On platforms update with GPIO
support, they can be used instead of a worst-case delay to verify that the
BUSY signal is off.

(Also includes a couple minor unrelated doc updates.)

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>

1 files changed, 95 insertions, 0 deletions

diff --git a/include/linux/gpio.h b/include/linux/gpio.h
new file mode 100644
index 00000000000..4987a84078e
--- /dev/null
+++ b/include/linux/gpio.h
@@ -0,0 +1,95 @@
+#ifndef __LINUX_GPIO_H
+#define __LINUX_GPIO_H
+
+/* see Documentation/gpio.txt */
+
+#ifdef CONFIG_GENERIC_GPIO
+#include <asm/gpio.h>
+
+#else
+
+/*
+ * Some platforms don't support the GPIO programming interface.
+ *
+ * In case some driver uses it anyway (it should normally have
+ * depended on GENERIC_GPIO), these routines help the compiler
+ * optimize out much GPIO-related code ... or trigger a runtime
+ * warning when something is wrongly called.
+ */
+
+static inline int gpio_is_valid(int number)
+{
+	return 0;
+}
+
+static inline int gpio_request(unsigned gpio, const char *label)
+{
+	return -ENOSYS;
+}
+
+static inline void gpio_free(unsigned gpio)
+{
+	/* GPIO can never have been requested */
+	WARN_ON(1);
+}
+
+static inline int gpio_direction_input(unsigned gpio)
+{
+	return -ENOSYS;
+}
+
+static inline int gpio_direction_output(unsigned gpio, int value)
+{
+	return -ENOSYS;
+}
+
+static inline int gpio_get_value(unsigned gpio)
+{
+	/* GPIO can never have been requested or set as {in,out}put */
+	WARN_ON(1);
+	return 0;
+}
+
+static inline void gpio_set_value(unsigned gpio, int value)
+{
+	/* GPIO can never have been requested or set as output */
+	WARN_ON(1);
+}
+
+static inline int gpio_cansleep(unsigned gpio)
+{
+	/* GPIO can never have been requested or set as {in,out}put */
+	WARN_ON(1);
+	return 0;
+}
+
+static inline int gpio_get_value_cansleep(unsigned gpio)
+{
+	/* GPIO can never have been requested or set as {in,out}put */
+	WARN_ON(1);
+	return 0;
+}
+
+static inline void gpio_set_value_cansleep(unsigned gpio, int value)
+{
+	/* GPIO can never have been requested or set as output */
+	WARN_ON(1);
+}
+
+static inline int gpio_to_irq(unsigned gpio)
+{
+	/* GPIO can never have been requested or set as input */
+	WARN_ON(1);
+	return -EINVAL;
+}
+
+static inline int irq_to_gpio(unsigned irq)
+{
+	/* irq can never have been returned from gpio_to_irq() */
+	WARN_ON(1);
+	return -EINVAL;
+}
+
+#endif
+
+#endif /* __LINUX_GPIO_H */