[PATCH v9 2/2] clk: Add (devm_)clk_get_optional() functions

[Phil Edworthy]

This adds clk_get_optional() and devm_clk_get_optional() functions to get
optional clocks.
They behave the same as (devm_)clk_get() except where there is no clock
producer. In this case, instead of returning -ENOENT, the function
returns NULL. This makes error checking simpler and allows
clk_prepare_enable, etc to be called on the returned reference
without additional checks.

Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
v9:
 - Add brackets after devm_clk_get so people know it's a function.
 - Add kernel doc for clk_get_optional().
v8:
 - Remove else clause
v7:
 - Instead of messing with the core functions, simply wrap them for the
   _optional() versions. By putting clk_get_optional() inline in the header
   file, we can get rid of the arch specific patches as well.
v6:
 - Add doxygen style comment for devm_clk_get_optional() args
v5:
 - No changes.
v4:
 - No changes.
v3:
 - No changes.
---
 drivers/clk/clk-devres.c | 11 +++++++++++
 include/linux/clk.h      | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/clk/clk-devres.c b/drivers/clk/clk-devres.c
index 12c87457eca1..8e8893168676 100644
--- a/drivers/clk/clk-devres.c
+++ b/drivers/clk/clk-devres.c
@@ -34,6 +34,17 @@ struct clk *devm_clk_get(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL(devm_clk_get);
 
+struct clk *devm_clk_get_optional(struct device *dev, const char *id)
+{
+	struct clk *clk = devm_clk_get(dev, id);
+
+	if (clk == ERR_PTR(-ENOENT))
+		return NULL;
+
+	return clk;
+}
+EXPORT_SYMBOL(devm_clk_get_optional);
+
 struct clk_bulk_devres {
 	struct clk_bulk_data *clks;
 	int num_clks;
diff --git a/include/linux/clk.h b/include/linux/clk.h
index a7773b5c0b9f..d8bc1a856b39 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -383,6 +383,17 @@ int __must_check devm_clk_bulk_get_all(struct device *dev,
  */
 struct clk *devm_clk_get(struct device *dev, const char *id);
 
+/**
+ * devm_clk_get_optional - lookup and obtain a managed reference to an optional
+ *			   clock producer.
+ * @dev: device for clock "consumer"
+ * @id: clock consumer ID
+ *
+ * Behaves the same as devm_clk_get() except where there is no clock producer.
+ * In this case, instead of returning -ENOENT, the function returns NULL.
+ */
+struct clk *devm_clk_get_optional(struct device *dev, const char *id);
+
 /**
  * devm_get_clk_from_child - lookup and obtain a managed reference to a
  *			     clock producer from child node.
@@ -718,6 +729,12 @@ static inline struct clk *devm_clk_get(struct device *dev, const char *id)
 	return NULL;
 }
 
+static inline struct clk *devm_clk_get_optional(struct device *dev,
+						const char *id)
+{
+	return NULL;
+}
+
 static inline int __must_check devm_clk_bulk_get(struct device *dev, int num_clks,
 						 struct clk_bulk_data *clks)
 {
@@ -862,6 +879,25 @@ static inline void clk_bulk_disable_unprepare(int num_clks,
 	clk_bulk_unprepare(num_clks, clks);
 }
 
+/**
+ * clk_get_optional - lookup and obtain a reference to an optional clock
+ *		      producer.
+ * @dev: device for clock "consumer"
+ * @id: clock consumer ID
+ *
+ * Behaves the same as clk_get() except where there is no clock producer. In
+ * this case, instead of returning -ENOENT, the function returns NULL.
+ */
+static inline struct clk *clk_get_optional(struct device *dev, const char *id)
+{
+	struct clk *clk = clk_get(dev, id);
+
+	if (clk == ERR_PTR(-ENOENT))
+		return NULL;
+
+	return clk;
+}
+
 #if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
 struct clk *of_clk_get(struct device_node *np, int index);
 struct clk *of_clk_get_by_name(struct device_node *np, const char *name);
-- 
2.17.1