With the current API, GPIOs are manipulated through an integer which
represents their unique number across the system. This poses problems in
terms of portability, scalability and flexibility: for instance, the
number of valid GPIOs for a given system is fixed at system time, and a
large array of that size is statically allocated to hold the GPIO
descriptors. Worse, GPIOs can be used without being properly allocated.

In order to improve the situation, the integer namespace must first get
away. This patch introduces an alternative GPIO API that uses opaque
handlers and refactor gpiolib's internals to work with these handlers
instead of GPIO numbers. The former integer-based API is still available
as a light wrapper around this new API.

This first step will then us to build more improvements for gpiolib,
like proper GPIO lookup functions per device and provider, and getting
rid of the static GPIO array and the ARCH_NR_GPIO configuration option.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpio/gpiolib.c        | 302 ++++++++++++++++++++++--------------------
 include/asm-generic/gpio.h    |  74 ++++++++---
 include/linux/gpio/consumer.h |  45 +++++++
 3 files changed, 261 insertions(+), 160 deletions(-)
 create mode 100644 include/linux/gpio/consumer.h

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 1c8d9e3..bf32511 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c

@@ -83,6 +83,32 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
 #endif
 }
 
+/**
+ * Convert a GPIO descriptor to the integer namespace.
+ * This should disappear in the future but is needed since we still
+ * use GPIO numbers for error messages and sysfs nodes
+ */
+static inline int desc_to_gpio(struct gpio_desc *desc)
+{
+	return desc - &gpio_desc[0];
+}
+
+/**
+ * Return the GPIO number of the passed descriptor relative to its chip
+ */
+int gpio_chip_offset(struct gpio_desc *desc)
+{
+	return (desc - &gpio_desc[0]) - desc->chip->base;
+}