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Subject[PATCH 2/3] gpiolib: implement gpiochip_reserve
Function gpiochip_reserve() reserves range of gpios to use with
platform code only, that is, this function used to mark specified
range of gpios unavailable for the dynamic gpio base allocator.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
---
drivers/gpio/gpiolib.c | 51 +++++++++++++++++++++++++++++++++++++++++--
include/asm-generic/gpio.h | 1 +
2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 81d81c9..2149e0c 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;
@@ -80,6 +81,48 @@ static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
return gpio_desc[gpio].chip;
}

+/**
+ * gpiochip_reserve() - reserve range of gpios to use with platform code only
+ * @start: starting gpio number
+ * @ngpio: number of gpios to reserve
+ * Context: potentially before irqs or kmalloc will work
+ *
+ * Returns a negative errno if any gpio within the range already reserved
+ * or registered. Otherwise it returns zero as a success code.
+ * Use this function to mark specified range of gpios unavailable for the
+ * dynamic gpio base allocator.
+ */
+int __must_check 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;
+}
+EXPORT_SYMBOL_GPL(gpiochip_reserve);
+
static int gpiochip_find_base(int ngpio)
{
int i;
@@ -87,9 +130,10 @@ 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;
@@ -97,7 +141,8 @@ static int gpiochip_find_base(int ngpio)
}
} else {
spare = 0;
- i -= chip->ngpio - 1;
+ if (chip)
+ i -= chip->ngpio - 1;
}
}

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 464c5b3..20f5d67 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 __must_check gpiochip_reserve(int start, int ngpio);

/* add/remove chips */
extern int gpiochip_add(struct gpio_chip *chip);
--
1.5.2.2


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