Add a mention about the _optional variants of (devm_)gpiod_get*().
Signed-off-by: Alexandre Courbot <[email protected]>
---
Documentation/gpio/consumer.txt | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index 76546324e968..6ce544191ca6 100644
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -53,7 +53,20 @@ with IS_ERR() (they will never return a NULL pointer).
-ENOENT will be returned
if and only if no GPIO has been assigned to the device/function/index triplet,
other error codes are used for cases where a GPIO has been assigned but an
error
occurred while trying to acquire it. This is useful to discriminate between
mere
-errors and an absence of GPIO for optional GPIO parameters.
+errors and an absence of GPIO for optional GPIO parameters. For the common
+pattern where a GPIO is optional, the gpiod_get_optional() and
+gpiod_get_index_optional() functions can be used. These functions return NULL
+instead of -ENOENT if no GPIO has been assigned to the requested function:
+
+
+ struct gpio_desc *gpiod_get_optional(struct device *dev,
+ const char *con_id,
+ enum gpiod_flags flags)
+
+ struct gpio_desc *gpiod_get_index_optional(struct device *dev,
+ const char *con_id,
+ unsigned int index,
+ enum gpiod_flags flags)
Device-managed variants of these functions are also defined:
@@ -65,6 +78,15 @@ Device-managed variants of these functions are also defined:
unsigned int idx,
enum gpiod_flags flags)
+ struct gpio_desc *devm_gpiod_get_optional(struct device *dev,
+ const char *con_id,
+ enum gpiod_flags flags)
+
+ struct gpio_desc * devm_gpiod_get_index_optional(struct device *dev,
+ const char *con_id,
+ unsigned int index,
+ enum gpiod_flags flags)
+
A GPIO descriptor can be disposed of using the gpiod_put() function:
void gpiod_put(struct gpio_desc *desc)
--
2.0.4
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