linux-kernel - [PATCH 1/3] misc: always assign miscdevice to file->private

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Message-Id: <1413678660-29669-1-git-send-email-martink@posteo.de>
Date:	Sun, 19 Oct 2014 02:30:58 +0200
From:	Martin Kepplinger <martink@...teo.de>
To:	gregkh@...uxfoundation.org
Cc:	arnd@...db.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, Martin Kepplinger <martink@...teo.de>
Subject: [PATCH 1/3] misc: always assign miscdevice to file->private_data in open()

As of now, a miscdevice driver has to provide an implementation of
the open() file operation if it wants to have misc_open() assign a
pointer to struct miscdevice to file->private_data for other file
operations to use (given the user calls open()).

This leads to situations where a miscdevice driver that doesn't need
internal operations during open() has to implement open() that only
returns immediately, in order to use the data in private_data in other
fops.

This provides consistent behaviour for miscdevice developers and will
always provide the pointer in private_data. A driver's open() fop would,
of course, just overwrite it, when using private_data itself.

Signed-off-by: Martin Kepplinger <martink@...teo.de>
---

The mentioned warning is appearently unrelated here, and happens on mainline
v3.17 awell -.- sorry for the confusion.

This applies to 3.17 and is a call for review and opinions. Especially on
the followup patches.

 drivers/char/misc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index ffa97d2..205ad4c 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -142,8 +142,8 @@ static int misc_open(struct inode * inode, struct file * file)

 	err = 0;
 	replace_fops(file, new_fops);
+	file->private_data = c;
 	if (file->f_op->open) {
-		file->private_data = c;
 		err = file->f_op->open(inode,file);
 	}
 fail:
-- 
1.7.10.4

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