linux-kernel - [PATCH v4 6/7] char: misc: Leverage revocable fops replacement

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Message-ID: <20250923075302.591026-7-tzungbi@kernel.org>
Date: Tue, 23 Sep 2025 07:53:01 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Benson Leung <bleung@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>
Cc: Jonathan Corbet <corbet@....net>,
	Shuah Khan <shuah@...nel.org>,
	Dawid Niedzwiecki <dawidn@...gle.com>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	chrome-platform@...ts.linux.dev,
	linux-kselftest@...r.kernel.org,
	tzungbi@...nel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>
Subject: [PATCH v4 6/7] char: misc: Leverage revocable fops replacement

Signed-off-by: Tzung-Bi Shih <tzungbi@...nel.org>
---
PoC patch.

v4:
- New in the series.

 drivers/char/misc.c        | 7 +++++++
 include/linux/miscdevice.h | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index 726516fb0a3b..fcbbb0b1af35 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -159,6 +159,13 @@ static int misc_open(struct inode *inode, struct file *file)
 
 	err = 0;
 	replace_fops(file, new_fops);
+
+	if (c->rp && c->rops) {
+		err = revocable_replace_fops(file, c->rp, c->rops);
+		if (err)
+			goto fail;
+	}
+
 	if (file->f_op->open)
 		err = file->f_op->open(inode, file);
 fail:
diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
index 7d0aa718499c..00f5c878266a 100644
--- a/include/linux/miscdevice.h
+++ b/include/linux/miscdevice.h
@@ -5,6 +5,7 @@
 #include <linux/list.h>
 #include <linux/types.h>
 #include <linux/device.h>
+#include <linux/revocable.h>
 
 /*
  *	These allocations are managed by device@...ana.org. If you need
@@ -92,6 +93,8 @@ struct miscdevice {
 	const struct attribute_group **groups;
 	const char *nodename;
 	umode_t mode;
+	struct revocable_provider *rp;
+	const struct revocable_operations *rops;
 };
 
 extern int misc_register(struct miscdevice *misc);
-- 
2.51.0.534.gc79095c0ca-goog