[PATCH v8 02/10] media: uvcvideo: add uvc_ctrl_get_boundary for getting default value

[Yunke Cao <yunkec@xxxxxxxxxx>]

Introduce uvc_ctrl_get_boundary(), making it easier to extend to
support compound controls and V4L2_CTRL_WHICH_MIN/MAX_VAL in the
following patches.

For now, it simply returns EINVAL for compound controls and calls
__query_v4l2_ctrl() for non-compound controls.

Reviewed-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
Signed-off-by: Yunke Cao <yunkec@xxxxxxxxxx>
---
Changelog since v7:
- Rename uvc_ctrl_get_fixed() to uvc_ctrl_get_boundary().
- Move refactor (introduce  __uvc_ctrl_get_boundary_std()) in this patch
  instead of in the patch where we implement compound control.
- Fix locking. uvc_ctrl_get_boundary() now acquires ctrl_mutex.
  __uvc_ctrl_get_boundary_std() calls __uvc_query_v4l2_ctrl() while
  holding the mutex.
- Define a uvc_ctrl_mapping_is_compound() for readability.

 drivers/media/usb/uvc/uvc_ctrl.c | 48 ++++++++++++++++++++++++++++++++
 drivers/media/usb/uvc/uvc_v4l2.c |  6 +---
 drivers/media/usb/uvc/uvcvideo.h |  2 ++
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 97f312020516..40a47e9a93a8 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -836,6 +836,12 @@ static void uvc_set_le_value(struct uvc_control_mapping *mapping,
 	}
 }
 
+static bool
+uvc_ctrl_mapping_is_compound(const struct uvc_control_mapping *mapping)
+{
+	return mapping->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES;
+}
+
 /* ------------------------------------------------------------------------
  * Terminal and unit management
  */
@@ -1742,6 +1748,48 @@ int uvc_ctrl_get(struct uvc_video_chain *chain,
 	return __uvc_ctrl_get(chain, ctrl, mapping, &xctrl->value);
 }
 
+int __uvc_ctrl_get_boundary_std(struct uvc_video_chain *chain,
+				struct uvc_control *ctrl,
+				struct uvc_control_mapping *mapping,
+				struct v4l2_ext_control *xctrl)
+{
+	struct v4l2_queryctrl qc = { .id = xctrl->id };
+
+	int ret = __uvc_query_v4l2_ctrl(chain, ctrl, mapping, &qc);
+
+	if (ret < 0)
+		return ret;
+
+	xctrl->value = qc.default_value;
+	return 0;
+}
+
+int uvc_ctrl_get_boundary(struct uvc_video_chain *chain,
+			  struct v4l2_ext_control *xctrl)
+{
+	struct uvc_control *ctrl;
+	struct uvc_control_mapping *mapping;
+	int ret;
+
+	if (mutex_lock_interruptible(&chain->ctrl_mutex))
+		return -ERESTARTSYS;
+
+	ctrl = uvc_find_control(chain, xctrl->id, &mapping);
+	if (!ctrl) {
+		ret = -EINVAL;
+		goto done;
+	}
+
+	if (uvc_ctrl_mapping_is_compound(mapping))
+		ret = -EINVAL;
+	else
+		ret = __uvc_ctrl_get_boundary_std(chain, ctrl, mapping, xctrl);
+
+done:
+	mutex_unlock(&chain->ctrl_mutex);
+	return ret;
+}
+
 int uvc_ctrl_set(struct uvc_fh *handle,
 	struct v4l2_ext_control *xctrl)
 {
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 4cc3fa6b8c98..d844da6f307c 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -1046,15 +1046,11 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
 
 	if (ctrls->which == V4L2_CTRL_WHICH_DEF_VAL) {
 		for (i = 0; i < ctrls->count; ++ctrl, ++i) {
-			struct v4l2_queryctrl qc = { .id = ctrl->id };
-
-			ret = uvc_query_v4l2_ctrl(chain, &qc);
+			ret = uvc_ctrl_get_boundary(chain, ctrl);
 			if (ret < 0) {
 				ctrls->error_idx = i;
 				return ret;
 			}
-
-			ctrl->value = qc.default_value;
 		}
 
 		return 0;
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 24c911aeebce..dce9e3ca764d 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -903,6 +903,8 @@ static inline int uvc_ctrl_rollback(struct uvc_fh *handle)
 }
 
 int uvc_ctrl_get(struct uvc_video_chain *chain, struct v4l2_ext_control *xctrl);
+int uvc_ctrl_get_boundary(struct uvc_video_chain *chain,
+			  struct v4l2_ext_control *xctrl);
 int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl);
 int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
 			   bool read);
-- 
2.38.0.rc1.362.ged0d419d3c-goog