linux-kernel - [PATCH v15 14/19] media: uvcvideo: Use the camera to clamp compound controls

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Message-Id: <20241114-uvc-roi-v15-14-64cfeb56b6f8@chromium.org>
Date: Thu, 14 Nov 2024 19:10:43 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans de Goede <hdegoede@...hat.com>, Ricardo Ribalda <ribalda@...nel.org>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Hans Verkuil <hverkuil@...all.nl>
Cc: Yunke Cao <yunkec@...omium.org>, linux-media@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v15 14/19] media: uvcvideo: Use the camera to clamp
 compound controls

Compound controls cannot e reliable clamped. There is plenty of space
for interpretation for the device manufacturer.

When we write a compound control, let the camera do the clamping and
return back to the user the value used by the device.

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 0dae5e8c3ca0..72ed7dc9cfc1 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2339,6 +2339,18 @@ int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl)
 
 	ctrl->dirty = 1;
 	ctrl->modified = 1;
+
+	/*
+	 * Compound controls cannot reliable clamp the value when they are
+	 * written to the device. Let the device do the clamping and read back
+	 * the value that the device is using. We do not need to return an
+	 * error if this fails.
+	 */
+	if (uvc_ctrl_mapping_is_compound(mapping) &&
+	    uvc_ctrl_is_readable(V4L2_CTRL_WHICH_CUR_VAL, ctrl, mapping))
+		uvc_mapping_get_xctrl_compound(chain, ctrl, mapping,
+					       V4L2_CTRL_WHICH_CUR_VAL, xctrl);
+
 	return 0;
 }
 

-- 
2.47.0.338.g60cca15819-goog