[PATCH master 1/2] clk: implement clk_get_optional helper

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Lack of clock can be ok at times and thus the clk API accepts NULL
arguments and treats them as no-op.

Linux provides a clk_get_optional function to simplify code with such
optional code, so let's provide an equivalent for barebox.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 include/linux/clk.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/clk.h b/include/linux/clk.h
index 8509d5ece9d5..82022e78e39d 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -932,4 +932,23 @@ static inline void clk_bulk_disable(int num_clks,
 
 #endif
 
+/**
+ * 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;
+}
+
 #endif
-- 
2.39.2