Introduce an helper function to get a video_device_context from file.
If no context has been bound to the file, return the video device
default context.
As a video device context lifetime is bound to the one of the file
handle it is associated with, and the intended user of this helper are
the v4l2_ioctl_ops handlers that operates on an open file handle, the
context returned by this function is guaranteed to be valid for the
whole function scope of the caller.
Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-dev.c | 15 +++++++++++++++
include/media/v4l2-dev.h | 30 ++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 73462191fd17..d92989d76cf0 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -1181,6 +1181,21 @@ void video_unregister_device(struct video_device *vdev)
}
EXPORT_SYMBOL(video_unregister_device);
+struct video_device_context *
+video_device_context_from_file(struct file *filp, struct video_device *vfd)
+{
+ struct v4l2_fh *vfh =
+ test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? filp->private_data
+ : NULL;
+
+ /* If the file handle has been bound to a context return it. */
+ if (vfh && vfh->context)
+ return vfh->context;
+
+ return vfd->default_context;
+}
+EXPORT_SYMBOL_GPL(video_device_context_from_file);
+
#if defined(CONFIG_MEDIA_CONTROLLER)
__must_check int video_device_pipeline_start(struct video_device *vdev,
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index b79b14e36a2a..32e61f9f9cb5 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -766,6 +766,36 @@ int video_device_init_context(struct video_device *vdev,
*/
void video_device_cleanup_context(struct video_device_context *ctx);
+/**
+ * video_device_context_from_file - Get the video device context associated with
+ * an open file handle
+ * @filp: The file handle
+ * @vdev: The video device
+ *
+ * If a video device context has been bound to an open file handle by a call
+ * to the VIDIOC_BIND_CONTEXT ioctl this function returns it, otherwise returns
+ * the default video device context.
+ *
+ * The intended callers of this helper are the driver-specific v4l2_ioctl_ops
+ * handlers, which receive as first argument a file pointer. By using this
+ * helper drivers can get the context associated with such file, if any.
+ * Otherwise, if the video device has not been bound to any media device
+ * context, the default video device context is returned.
+ *
+ * As video device contexts are reference counted and their lifetime is
+ * guaranteed to be at least the one of the file handle they are associated
+ * with, callers of this function are guaranteed to always receive a valid
+ * context reference by this function. The reference will remain valid for the
+ * whole function scope of the caller that has received the open file handle as
+ * argument. Likewise, accessing the media context from the video device context
+ * returned by this function is always safe within the same function scope.
+ *
+ * This function does not increase the reference count of the returned video
+ * device context.
+ */
+struct video_device_context *
+video_device_context_from_file(struct file *filp, struct video_device *vdev);
+
#endif /* CONFIG_MEDIA_CONTROLLER */
#endif /* _V4L2_DEV_H */
--
2.46.0
