linux-kernel - [PATCH] linux/kernel.h: add container

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Message-Id: <20200827013636.149307-1-allen.lkml@gmail.com>
Date:   Thu, 27 Aug 2020 07:06:36 +0530
From:   Allen Pais <allen.lkml@...il.com>
To:     torvalds@...ux-foundation.org
Cc:     akpm@...ux-foundation.org, keescook@...omium.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        Allen Pais <allen.lkml@...il.com>,
        "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH] linux/kernel.h: add container_from()

Introduce container_from() as a generic helper instead of
sub-systems defining a private from_* API
(Eg: from_tasklets recently introduced in
12cc923f1ccc: Tasklet: Introduce new initialization API)

The helper is similar to container_of() in argument order
with the difference of naming the containing structure instead
of having to specify its type.

Suggested-by: James E.J. Bottomley <James.Bottomley@...senPartnership.com>
Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Suggested-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Allen Pais <allen.lkml@...il.com>
---
 include/linux/kernel.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 500def620d8f..9d446324a8be 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -1019,6 +1019,15 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
 			 "pointer type mismatch in container_of()");	\
 	IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :			\
 		((type *)(__mptr - offsetof(type, member))); })
+/**
+ * container_from - cast a member of a structure out to the containing structure
+ * @ptr:	the pointer to the member.
+ * @container:	the type of the container struct.
+ * @member:	the name of the member within the struct.
+ *
+ */
+#define container_from(ptr, container, member)	\
+	container_of(ptr, typeof(*container), member)
 
 /* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
-- 
2.25.1