[PATCH 3/5] media: uvcvideo: Probe the PLF characteristics

[Ricardo Ribalda <ribalda@xxxxxxxxxxxx>]

The UVC 1.5 standard defines 4 values for the PLF control: Off, 50Hz,
60Hz and Auto. But it does not clearly define if all the values must be
implemented or not.

Instead of just using the UVC version to determine what the PLF control
can do, probe it.

Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 54 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 50 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 67522143c6c85..9a0b81aca30d1 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -501,12 +501,58 @@ static int __uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
 static int uvc_ctrl_add_plf_mapping(struct uvc_video_chain *chain,
 	struct uvc_control *ctrl, const struct uvc_control_mapping *mapping)
 {
+	const struct uvc_control_mapping *out_mapping =
+					&uvc_ctrl_power_line_mapping_uvc11;
+	u8 init_val;
+	u8 *buf;
+	int ret;
+
+	buf = kmalloc(sizeof(*buf), GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	/* Save the default PLF value, so we can restore it. */
+	ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	/* If we cannot read the control skip it. */
+	if (ret) {
+		kfree(buf);
+		return ret;
+	}
+	init_val = *buf;
+
+	/* If PLF value cannot be set to off, it is limited. */
+	*buf = V4L2_CID_POWER_LINE_FREQUENCY_DISABLED;
+	ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	if (ret) {
+		out_mapping = &uvc_ctrl_power_line_mapping_limited;
+		goto end;
+	}
+
+	/* UVC 1.1 does not define auto, we can exit. */
 	if (chain->dev->uvc_version < 0x150)
-		return __uvc_ctrl_add_mapping(chain, ctrl,
-					      &uvc_ctrl_power_line_mapping_uvc11);
+		goto end;
+
+	/* Check if the device supports auto. */
+	*buf = V4L2_CID_POWER_LINE_FREQUENCY_AUTO;
+	ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+			     chain->dev->intfnum, ctrl->info.selector,
+			     buf, sizeof(*buf));
+	if (!ret)
+		out_mapping = &uvc_ctrl_power_line_mapping_uvc15;
+
+end:
+	/* Restore initial value and add mapping. */
+	*buf = init_val;
+	uvc_query_ctrl(chain->dev, UVC_SET_CUR, ctrl->entity->id,
+		       chain->dev->intfnum, ctrl->info.selector,
+		       buf, sizeof(*buf));
 
-	return __uvc_ctrl_add_mapping(chain, ctrl,
-				      &uvc_ctrl_power_line_mapping_uvc15);
+	kfree(buf);
+	return __uvc_ctrl_add_mapping(chain, ctrl, out_mapping);
 }
 
 static const struct uvc_control_mapping uvc_ctrl_mappings[] = {

-- 
2.44.0.291.gc1ea87d7ee-goog