media: cec: move cec_get/put_device to header

Move cec_get/put_device to the media/cec.h header. This
allows CEC drivers to use this.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/include/media/cec.h b/include/media/cec.h
index 07d2ee8a3904..16b412b3131b 100644
--- a/include/media/cec.h
+++ b/include/media/cec.h
@@ -298,6 +298,37 @@ struct cec_adapter {
 	char input_phys[40];
 };
 
+static inline int cec_get_device(struct cec_adapter *adap)
+{
+	struct cec_devnode *devnode = &adap->devnode;
+
+	/*
+	 * Check if the cec device is available. This needs to be done with
+	 * the devnode->lock held to prevent an open/unregister race:
+	 * without the lock, the device could be unregistered and freed between
+	 * the devnode->registered check and get_device() calls, leading to
+	 * a crash.
+	 */
+	mutex_lock(&devnode->lock);
+	/*
+	 * return ENODEV if the cec device has been removed
+	 * already or if it is not registered anymore.
+	 */
+	if (!devnode->registered) {
+		mutex_unlock(&devnode->lock);
+		return -ENODEV;
+	}
+	/* and increase the device refcount */
+	get_device(&devnode->dev);
+	mutex_unlock(&devnode->lock);
+	return 0;
+}
+
+static inline void cec_put_device(struct cec_adapter *adap)
+{
+	put_device(&adap->devnode.dev);
+}
+
 static inline void *cec_get_drvdata(const struct cec_adapter *adap)
 {
 	return adap->priv;