[net-next RFC PATCH 1/2] net: mdio: implement mdio_mutex_nested guard() variant

[Christian Marangi <ansuelsmth@gmail.com>]

Implement mdio_mutex_nested guard() variant.

guard() compes from the cleanup.h API that define handy class to
define the lifecycle of a critical section.

Many driver makes use of the mutex_lock_nested()/mutex_unlock() hence it
might be sensible to provide a variant of the generic guard(mutex),
guard(mdio_mutex_nested) to also support drivers that use
mutex_lock_nested with MDIO_MUTEX_NESTED.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 include/linux/mdio.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/mdio.h b/include/linux/mdio.h
index 68f8d2e970d4..f13a02d05eb2 100644
--- a/include/linux/mdio.h
+++ b/include/linux/mdio.h
@@ -8,6 +8,8 @@
 
 #include <uapi/linux/mdio.h>
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
+#include <linux/mutex.h>
 #include <linux/mod_devicetable.h>
 
 struct gpio_desc;
@@ -25,6 +27,9 @@ enum mdio_mutex_lock_class {
 	MDIO_MUTEX_NESTED,
 };
 
+DEFINE_GUARD(mdio_mutex_nested, struct mutex *,
+	     mutex_lock_nested(_T, MDIO_MUTEX_NESTED), mutex_unlock(_T))
+
 struct mdio_device {
 	struct device dev;
 
-- 
2.45.1