linux-kernel - [PATCH v3] regmap: Call regmap_debugfs_exit() prior to

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Date:   Fri,  7 Jan 2022 13:33:07 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     broonie@...nel.org
Cc:     matthias.schiffer@...tq-group.com, linux-kernel@...r.kernel.org,
        Fabio Estevam <festevam@...x.de>
Subject: [PATCH v3] regmap: Call regmap_debugfs_exit() prior to _init()

From: Fabio Estevam <festevam@...x.de>

Since commit cffa4b2122f5 ("regmap: debugfs: Fix a memory leak when
calling regmap_attach_dev"), the following debugfs error is seen
on i.MX boards:

debugfs: Directory 'dummy-iomuxc-gpr@...0000' with parent 'regmap' already present!

In the attempt to fix the memory leak, the above commit added a NULL check
for map->debugfs_name. For the first debufs entry, map->debugfs_name is NULL
and then the new name is allocated via kasprintf().

For the second debugfs entry, map->debugfs_name() is no longer NULL, so
it will keep using the old entry name and the duplicate name error is seen.

Quoting Mark Brown:

"That means that if the device gets freed we'll end up with the old debugfs
file hanging around pointing at nothing.
...
To be more explicit this means we need a call to regmap_debugfs_exit()
which will clean up all the existing debugfs stuff before we loose
references to it."

Call regmap_debugfs_exit() prior to regmap_debugfs_init() to fix
the problem.

Tested on i.MX6Q and i.MX6SX boards.

Fixes: cffa4b2122f5 ("regmap: debugfs: Fix a memory leak when calling regmap_attach_dev")
Suggested-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Fabio Estevam <festevam@...x.de>
---
Changes since v2:
- Use regmap_debugfs_exit() as suggested by Mark.

 drivers/base/regmap/regmap.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 21a0c2562ec0..f7811641ed5a 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -647,6 +647,7 @@ int regmap_attach_dev(struct device *dev, struct regmap *map,
 	if (ret)
 		return ret;

+	regmap_debugfs_exit(map);
 	regmap_debugfs_init(map);

 	/* Add a devres resource for dev_get_regmap() */
-- 
2.25.1