[media] v4l2-dev/ioctl: determine the valid ioctls upfront

Rather than testing whether an ioctl is implemented in the driver or not
every time the ioctl is called, do it upfront when the device is registered.

This also allows a driver to disable certain ioctls based on the capabilities
of the detected board, something you can't do today without creating separate
v4l2_ioctl_ops structs for each new variation.

For the most part it is pretty straightforward, but for control ioctls a flag
is needed since it is possible that you have per-filehandle controls, and that
can't be determined upfront of course.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index d00b9d3511f2..a5ecec66d3c8 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -126,6 +126,7 @@ struct video_device
 
         /* ioctl callbacks */
         const struct v4l2_ioctl_ops *ioctl_ops;
+        DECLARE_BITMAP(valid_ioctls, BASE_VIDIOC_PRIVATE);
 
         /* serialization lock */
         DECLARE_BITMAP(dont_use_lock, BASE_VIDIOC_PRIVATE);
@@ -184,6 +185,16 @@ static inline void v4l2_dont_use_lock(struct video_device *vdev, unsigned int cm
                 set_bit(_IOC_NR(cmd), vdev->dont_use_lock);
 }
 
+/* Mark that this command isn't implemented, must be called before
+   video_device_register. See also the comments in determine_valid_ioctls().
+   This function allows drivers to provide just one v4l2_ioctl_ops struct, but
+   disable ioctls based on the specific card that is actually found. */
+static inline void v4l2_dont_use_cmd(struct video_device *vdev, unsigned int cmd)
+{
+        if (_IOC_NR(cmd) < BASE_VIDIOC_PRIVATE)
+                set_bit(_IOC_NR(cmd), vdev->valid_ioctls);
+}
+
 /* helper functions to access driver private data. */
 static inline void *video_get_drvdata(struct video_device *vdev)
 {