raw: deprecate the raw driver

The raw driver has been replaced by O_DIRECT support on the block device
in 2002.  Deprecate it to prepare for removal in a few kernel releases.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/char/raw.c

@@ -63,6 +63,11 @@ static int raw_open(struct inode *inode, struct file *filp)
 		return 0;
 	}
 
+	pr_warn_ratelimited(
+		"process %s (pid %d) is using the deprecated raw device\n"
+		"support will be removed in Linux 5.14.\n",
+		current->comm, current->pid);
+
 	mutex_lock(&raw_mutex);
 
 	/*