linux-kernel - [PATCH] driver core: Clarify which counterparts to use to device

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Date:   Thu, 18 Apr 2019 19:41:56 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: [PATCH] driver core: Clarify which counterparts to use to device_add()

From: Borislav Petkov <bp@...e.de>

It is not absolutely clear from the docs how the cleanup path after
device_add() should look like so spell it out explicitly.

No functional changes, just documentation.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
---
 drivers/base/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4aeaa0c92bda..fd7511e04e62 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1999,6 +1999,11 @@ static int device_private_init(struct device *dev)
  * NOTE: _Never_ directly free @dev after calling this function, even
  * if it returned an error! Always use put_device() to give up your
  * reference instead.
+ *
+ * Rule of thumb is: if device_add() succeeds, you should call
+ * device_del() when you want to get rid of it. If device_add() has
+ * *not* succeeded, use *only* put_device() to drop the reference
+ * count.
  */
 int device_add(struct device *dev)
 {
-- 
2.21.0