linux-kernel - [PATCH 3.4 54/92] regmap: debugfs: Don't bother actually printing when calculating max length

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Date:	Mon, 18 Apr 2016 18:45:59 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 54/92] regmap: debugfs: Don't bother actually printing when calculating max length

From: Mark Brown <broonie@...nel.org>

3.4.112-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit 176fc2d5770a0990eebff903ba680d2edd32e718 upstream.

The in kernel snprintf() will conveniently return the actual length of
the printed string even if not given an output beffer at all so just do
that rather than relying on the user to pass in a suitable buffer,
ensuring that we don't need to worry if the buffer was truncated due to
the size of the buffer passed in.

Reported-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 drivers/base/regmap/regmap-debugfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index d805eb5..023a9d7 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -23,8 +23,7 @@ static struct dentry *regmap_debugfs_root;
 /* Calculate the length of a fixed format  */
 static size_t regmap_calc_reg_len(int max_val, char *buf, size_t buf_size)
 {
-	snprintf(buf, buf_size, "%x", max_val);
-	return strlen(buf);
+	return snprintf(NULL, 0, "%x", max_val);
 }
 
 static ssize_t regmap_name_read_file(struct file *file,
-- 
1.9.1