Re: [PATCH] uvcvideo: Apply flags from device to actual properties

[Edgar Thier <info@xxxxxxxxxxxxxx>]

Use flags the device exposes for UVC controls.
This allows the device to define which property flags are set.

Since some cameras offer auto-adjustments for properties (e.g. auto-gain),
the values of other properties (e.g. gain) can change in the camera.
Examining the flags ensures that the driver is aware of such properties.

Signed-off-by: Edgar Thier <info@xxxxxxxxxxxxxx>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 64 ++++++++++++++++++++++++++++++----------
 1 file changed, 49 insertions(+), 15 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 20397aba..8f902a41 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1629,6 +1629,40 @@ static void uvc_ctrl_fixup_xu_info(struct uvc_device *dev,
 	}
 }

+/*
+ * Retrieve flags for a given control
+ */
+static int uvc_ctrl_get_flags(struct uvc_device *dev, const struct uvc_control *ctrl,
+	const struct uvc_control_info *info)
+{
+	u8 *data;
+	int ret = 0;
+	int flags = 0;
+
+	data = kmalloc(2, GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
+						 info->selector, data, 1);
+	if (ret < 0) {
+		uvc_trace(UVC_TRACE_CONTROL,
+				  "GET_INFO failed on control %pUl/%u (%d).\n",
+				  info->entity, info->selector, ret);
+	} else {
+		flags = UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX
+			| UVC_CTRL_FLAG_GET_RES | UVC_CTRL_FLAG_GET_DEF
+			| (data[0] & UVC_CONTROL_CAP_GET ?
+			   UVC_CTRL_FLAG_GET_CUR : 0)
+			| (data[0] & UVC_CONTROL_CAP_SET ?
+			   UVC_CTRL_FLAG_SET_CUR : 0)
+			| (data[0] & UVC_CONTROL_CAP_AUTOUPDATE ?
+			   UVC_CTRL_FLAG_AUTO_UPDATE : 0);
+	}
+	kfree(data);
+	return flags;
+}
+
 /*
  * Query control information (size and flags) for XU controls.
  */
@@ -1636,6 +1670,7 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,
 	const struct uvc_control *ctrl, struct uvc_control_info *info)
 {
 	u8 *data;
+	int flags;
 	int ret;

 	data = kmalloc(2, GFP_KERNEL);
@@ -1659,24 +1694,15 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,

 	info->size = le16_to_cpup((__le16 *)data);

-	/* Query the control information (GET_INFO) */
-	ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
-			     info->selector, data, 1);
-	if (ret < 0) {
+	flags = uvc_ctrl_get_flags(dev, ctrl, info);
+
+	if (flags < 0) {
 		uvc_trace(UVC_TRACE_CONTROL,
-			  "GET_INFO failed on control %pUl/%u (%d).\n",
-			  info->entity, info->selector, ret);
+			  "Failed to retrieve flags (%d).\n", ret);
+ 		ret = flags;
 		goto done;
 	}
-
-	info->flags = UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX
-		    | UVC_CTRL_FLAG_GET_RES | UVC_CTRL_FLAG_GET_DEF
-		    | (data[0] & UVC_CONTROL_CAP_GET ?
-		       UVC_CTRL_FLAG_GET_CUR : 0)
-		    | (data[0] & UVC_CONTROL_CAP_SET ?
-		       UVC_CTRL_FLAG_SET_CUR : 0)
-		    | (data[0] & UVC_CONTROL_CAP_AUTOUPDATE ?
-		       UVC_CTRL_FLAG_AUTO_UPDATE : 0);
+	info->flags = flags;

 	uvc_ctrl_fixup_xu_info(dev, ctrl, info);

@@ -1890,6 +1916,7 @@ static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
 	const struct uvc_control_info *info)
 {
 	int ret = 0;
+	int flags = 0;

 	ctrl->info = *info;
 	INIT_LIST_HEAD(&ctrl->info.mappings);
@@ -1902,6 +1929,13 @@ static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
 		goto done;
 	}

+	flags = uvc_ctrl_get_flags(dev, ctrl, info);
+	if (flags < 0)
+		uvc_trace(UVC_TRACE_CONTROL,
+			  "Failed to retrieve flags (%d).\n", ret);
+	else
+		ctrl->info.flags = flags;
+
 	ctrl->initialized = 1;

 	uvc_trace(UVC_TRACE_CONTROL, "Added control %pUl/%u to device %s "
-- 
2.14.2