of/gpio: Implement of_get_gpio_flags()

This adds a new function, of_get_gpio_flags, which is like
of_get_gpio(), but accepts a new "flags" argument.  This new function
will be used by the drivers that need to retrieve additional GPIO
information, such as active-low flag.

Also, this changes the default ("simple") .xlate routine to warn about
bogus (< 2) #gpio-cells usage: the second cell should always be present
for GPIO flags.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 63 insertions, 11 deletions

diff --git a/drivers/of/gpio.c b/drivers/of/gpio.c
index 7cd7301b5839..a4ba217116eb 100644
--- a/drivers/of/gpio.c
+++ b/drivers/of/gpio.c
@@ -19,14 +19,17 @@
 #include <asm/prom.h>
 
 /**
- * of_get_gpio - Get a GPIO number from the device tree to use with GPIO API
+ * of_get_gpio_flags - Get a GPIO number and flags to use with GPIO API
  * @np:         device node to get GPIO from
  * @index:      index of the GPIO
+ * @flags:      a flags pointer to fill in
  *
  * Returns GPIO number to use with Linux generic GPIO API, or one of the errno
- * value on the error condition.
+ * value on the error condition. If @flags is not NULL the function also fills
+ * in flags for the GPIO.
  */
-int of_get_gpio(struct device_node *np, int index)
+int of_get_gpio_flags(struct device_node *np, int index,
+                      enum of_gpio_flags *flags)
 {
         int ret;
         struct device_node *gc;
@@ -59,7 +62,11 @@ int of_get_gpio(struct device_node *np, int index)
                 goto err1;
         }
 
-        ret = of_gc->xlate(of_gc, np, gpio_spec);
+        /* .xlate might decide to not fill in the flags, so clear it. */
+        if (flags)
+                *flags = 0;
+
+        ret = of_gc->xlate(of_gc, np, gpio_spec, flags);
         if (ret < 0)
                 goto err1;
 
@@ -70,26 +77,41 @@ err0:
         pr_debug("%s exited with status %d\n", __func__, ret);
         return ret;
 }
-EXPORT_SYMBOL(of_get_gpio);
+EXPORT_SYMBOL(of_get_gpio_flags);
 
 /**
- * of_gpio_simple_xlate - translate gpio_spec to the GPIO number
+ * of_gpio_simple_xlate - translate gpio_spec to the GPIO number and flags
  * @of_gc:      pointer to the of_gpio_chip structure
  * @np:         device node of the GPIO chip
  * @gpio_spec:  gpio specifier as found in the device tree
+ * @flags:      a flags pointer to fill in
  *
  * This is simple translation function, suitable for the most 1:1 mapped
  * gpio chips. This function performs only one sanity check: whether gpio
  * is less than ngpios (that is specified in the gpio_chip).
  */
 int of_gpio_simple_xlate(struct of_gpio_chip *of_gc, struct device_node *np,
-                         const void *gpio_spec)
+                         const void *gpio_spec, enum of_gpio_flags *flags)
 {
         const u32 *gpio = gpio_spec;
 
+        /*
+         * We're discouraging gpio_cells < 2, since that way you'll have to
+         * write your own xlate function (that will have to retrive the GPIO
+         * number and the flags from a single gpio cell -- this is possible,
+         * but not recommended).
+         */
+        if (of_gc->gpio_cells < 2) {
+                WARN_ON(1);
+                return -EINVAL;
+        }
+
         if (*gpio > of_gc->gc.ngpio)
                 return -EINVAL;
 
+        if (flags)
+                *flags = gpio[1];
+
         return *gpio;
 }
 EXPORT_SYMBOL(of_gpio_simple_xlate);
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index 67db101d0eb8..e25abf610cb6 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -14,9 +14,22 @@
 #ifndef __LINUX_OF_GPIO_H
 #define __LINUX_OF_GPIO_H
 
+#include <linux/compiler.h>
+#include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/gpio.h>
 
+struct device_node;
+
+/*
+ * This is Linux-specific flags. By default controllers' and Linux' mapping
+ * match, but GPIO controllers are free to translate their own flags to
+ * Linux-specific in their .xlate callback. Though, 1:1 mapping is recommended.
+ */
+enum of_gpio_flags {
+        OF_GPIO_ACTIVE_LOW = 0x1,
+};
+
 #ifdef CONFIG_OF_GPIO
 
 /*
@@ -26,7 +39,7 @@ struct of_gpio_chip {
         struct gpio_chip gc;
         int gpio_cells;
         int (*xlate)(struct of_gpio_chip *of_gc, struct device_node *np,
-                     const void *gpio_spec);
+                     const void *gpio_spec, enum of_gpio_flags *flags);
 };
 
 static inline struct of_gpio_chip *to_of_gpio_chip(struct gpio_chip *gc)
@@ -50,20 +63,37 @@ static inline struct of_mm_gpio_chip *to_of_mm_gpio_chip(struct gpio_chip *gc)
         return container_of(of_gc, struct of_mm_gpio_chip, of_gc);
 }
 
-extern int of_get_gpio(struct device_node *np, int index);
+extern int of_get_gpio_flags(struct device_node *np, int index,
+                             enum of_gpio_flags *flags);
+
 extern int of_mm_gpiochip_add(struct device_node *np,
                               struct of_mm_gpio_chip *mm_gc);
 extern int of_gpio_simple_xlate(struct of_gpio_chip *of_gc,
                                 struct device_node *np,
-                                const void *gpio_spec);
+                                const void *gpio_spec,
+                                enum of_gpio_flags *flags);
 #else
 
 /* Drivers may not strictly depend on the GPIO support, so let them link. */
-static inline int of_get_gpio(struct device_node *np, int index)
+static inline int of_get_gpio_flags(struct device_node *np, int index,
+                                    enum of_gpio_flags *flags)
 {
         return -ENOSYS;
 }
 
 #endif /* CONFIG_OF_GPIO */
 
+/**
+ * of_get_gpio - Get a GPIO number to use with GPIO API
+ * @np:         device node to get GPIO from
+ * @index:      index of the GPIO
+ *
+ * Returns GPIO number to use with Linux generic GPIO API, or one of the errno
+ * value on the error condition.
+ */
+static inline int of_get_gpio(struct device_node *np, int index)
+{
+        return of_get_gpio_flags(np, index, NULL);
+}
+
 #endif /* __LINUX_OF_GPIO_H */