gpiochip_reserve()

Add a new function gpiochip_reserve() to reserve ranges of gpios that platform
code has pre-allocated.  That is, this marks gpio numbers which will be
claimed by drivers that haven't yet been loaded, and thus are not available
for dynamic gpio number allocation.

[akpm@linux-foundation.org: remove unneeded __must_check]
[david-b@pacbell.net: don't export gpiochip_reserve (section fix)]
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
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>

2 files changed, 48 insertions, 3 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 2ba6127c4fae..24c62b848bf9 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -43,6 +43,7 @@ struct gpio_desc {
 /* flag symbols are bit numbers */
 #define FLAG_REQUESTED  0
 #define FLAG_IS_OUT     1
+#define FLAG_RESERVED   2
 
 #ifdef CONFIG_DEBUG_FS
         const char              *label;
@@ -88,9 +89,10 @@ static int gpiochip_find_base(int ngpio)
         int base = -ENOSPC;
 
         for (i = ARCH_NR_GPIOS - 1; i >= 0 ; i--) {
-                struct gpio_chip *chip = gpio_desc[i].chip;
+                struct gpio_desc *desc = &gpio_desc[i];
+                struct gpio_chip *chip = desc->chip;
 
-                if (!chip) {
+                if (!chip && !test_bit(FLAG_RESERVED, &desc->flags)) {
                         spare++;
                         if (spare == ngpio) {
                                 base = i;
@@ -98,7 +100,8 @@ static int gpiochip_find_base(int ngpio)
                         }
                 } else {
                         spare = 0;
-                        i -= chip->ngpio - 1;
+                        if (chip)
+                                i -= chip->ngpio - 1;
                 }
         }
 
@@ -108,6 +111,47 @@ static int gpiochip_find_base(int ngpio)
 }
 
 /**
+ * gpiochip_reserve() - reserve range of gpios to use with platform code only
+ * @start: starting gpio number
+ * @ngpio: number of gpios to reserve
+ * Context: platform init, potentially before irqs or kmalloc will work
+ *
+ * Returns a negative errno if any gpio within the range is already reserved
+ * or registered, else returns zero as a success code.  Use this function
+ * to mark a range of gpios as unavailable for dynamic gpio number allocation,
+ * for example because its driver support is not yet loaded.
+ */
+int __init gpiochip_reserve(int start, int ngpio)
+{
+        int ret = 0;
+        unsigned long flags;
+        int i;
+
+        if (!gpio_is_valid(start) || !gpio_is_valid(start + ngpio))
+                return -EINVAL;
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        for (i = start; i < start + ngpio; i++) {
+                struct gpio_desc *desc = &gpio_desc[i];
+
+                if (desc->chip || test_bit(FLAG_RESERVED, &desc->flags)) {
+                        ret = -EBUSY;
+                        goto err;
+                }
+
+                set_bit(FLAG_RESERVED, &desc->flags);
+        }
+
+        pr_debug("%s: reserved gpios from %d to %d\n",
+                 __func__, start, start + ngpio - 1);
+err:
+        spin_unlock_irqrestore(&gpio_lock, flags);
+
+        return ret;
+}
+
+/**
  * gpiochip_add() - register a gpio_chip
  * @chip: the chip to register, with chip->base initialized
  * Context: potentially before irqs or kmalloc will work
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 464c5b334dc2..ecf675a59d21 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -74,6 +74,7 @@ struct gpio_chip {
 
 extern const char *gpiochip_is_requested(struct gpio_chip *chip,
                         unsigned offset);
+extern int __init __must_check gpiochip_reserve(int start, int ngpio);
 
 /* add/remove chips */
 extern int gpiochip_add(struct gpio_chip *chip);