This is like container_of() but it has an assert to ensure that it's
using the first struct member.
Co-developed-by: Dan Carpenter <dan.carpen...@linaro.org>
Signed-off-by: Dan Carpenter <dan.carpen...@linaro.org>
Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
---
include/linux/container_of.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
index 713890c867be..928c5865c1b4 100644
--- a/include/linux/container_of.h
+++ b/include/linux/container_of.h
@@ -22,6 +22,24 @@
"pointer type mismatch in container_of()"); \
((type *)(__mptr - offsetof(type, member))); })
+/**
+ * container_first - cast first 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.
+ *
+ * WARNING: any const qualifier of @ptr is lost.
+ */
+#define container_first(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()"); \
+ static_assert(offsetof(type, member) == 0, "not first member"); \
+ ((type *)(__mptr - offsetof(type, member))); })
+
+
/**
* container_of_const - cast a member of a structure out to the containing
* structure and preserve the const-ness of the pointer
--
2.34.1
