[PATCH] clk: implement clk_to_clk_hw using container_of_safe

[Ahmad Fatoum <ahmad@a3f.at>]

We basically opencode container_of_safe. The kernel implementation of
container_of has also got a better diagnostic for mismatched arguments,
so let's import it and use it.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
---
 include/linux/clk.h          |  3 ++-
 include/linux/container_of.h | 40 ++++++++++++++++++++++++++++++++++++
 include/linux/kernel.h       | 12 +----------
 3 files changed, 43 insertions(+), 12 deletions(-)
 create mode 100644 include/linux/container_of.h

diff --git a/include/linux/clk.h b/include/linux/clk.h
index 29c697a00bd9..c78132d40582 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -13,6 +13,7 @@
 #include <linux/err.h>
 #include <linux/spinlock.h>
 #include <linux/stringify.h>
+#include <linux/container_of.h>
 #include <xfuncs.h>
 
 struct device;
@@ -296,7 +297,7 @@ static inline struct clk *clk_hw_to_clk(const struct clk_hw *hw)
 
 static inline struct clk_hw *clk_to_clk_hw(const struct clk *clk)
 {
-	return IS_ERR(clk) ? ERR_CAST(clk) : (struct clk_hw *)container_of(clk, struct clk_hw, clk);
+	return container_of_safe(clk, struct clk_hw, clk);
 }
 
 struct clk_div_table {
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
new file mode 100644
index 000000000000..2f4944b791b8
--- /dev/null
+++ b/include/linux/container_of.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CONTAINER_OF_H
+#define _LINUX_CONTAINER_OF_H
+
+#include <linux/build_bug.h>
+#include <linux/err.h>
+
+#define typeof_member(T, m)	typeof(((T*)0)->m)
+
+/**
+ * container_of - cast a member of a structure out to the containing structure
+ * @ptr:	the pointer to the member.
+ * @type:	the type of the container struct this is embedded in.
+ * @member:	the name of the member within the struct.
+ *
+ */
+#define container_of(ptr, type, member) ({				\
+	void *__mptr = (void *)(ptr);					\
+	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+		      __same_type(*(ptr), void),			\
+		      "pointer type mismatch in container_of()");	\
+	((type *)(__mptr - offsetof(type, member))); })
+
+/**
+ * container_of_safe - cast a member of a structure out to the containing structure
+ * @ptr:	the pointer to the member.
+ * @type:	the type of the container struct this is embedded in.
+ * @member:	the name of the member within the struct.
+ *
+ * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
+ */
+#define container_of_safe(ptr, type, member) ({				\
+	void *__mptr = (void *)(ptr);					\
+	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+		      __same_type(*(ptr), void),			\
+		      "pointer type mismatch in container_of_safe()");	\
+	IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :			\
+		((type *)(__mptr - offsetof(type, member))); })
+
+#endif	/* _LINUX_CONTAINER_OF_H */
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 44fc02df0bf9..0eb7bd21fe93 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -7,6 +7,7 @@
 #include <linux/barebox-wrapper.h>
 #include <linux/limits.h>
 #include <linux/math64.h>
+#include <linux/container_of.h>
 
 #define ALIGN(x, a)		__ALIGN_MASK(x, (typeof(x))(a) - 1)
 #define ALIGN_DOWN(x, a)	ALIGN((x) - ((a) - 1), (a))
@@ -256,17 +257,6 @@ extern int hex_to_bin(char ch);
 extern int __must_check hex2bin(u8 *dst, const char *src, size_t count);
 extern char *bin2hex(char *dst, const void *src, size_t count);
 
-/**
- * container_of - cast a member of a structure out to the containing structure
- * @ptr:	the pointer to the member.
- * @type:	the type of the container struct this is embedded in.
- * @member:	the name of the member within the struct.
- *
- */
-#define container_of(ptr, type, member) ({			\
-	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
-	(type *)( (char *)__mptr - offsetof(type,member) );})
-
 /*
  * swap - swap value of @a and @b
  */
-- 
2.38.4