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>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 2ba6127c4fae5f2c7dcc8af3b39d021cc7a25c95..24c62b848bf976dea7eabd0c48684e561d0d29cc 100644 (file)
--- 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;
                }
        }
 
@@ -107,6 +110,47 @@ static int gpiochip_find_base(int ngpio)
        return base;
 }
 
+/**
+ * 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

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 464c5b334dc27695ae8511991d871a6affce6e96..ecf675a59d2197d00f934aa89f4506028a725839 100644 (file)
--- 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);