linux-kernel - [PATCH v2] media: uvcvideo: Fix support for V4L2_CTRL_FLAG_HAS_WHICH_MIN

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Message-Id: <20251119-uvc-fix-which-v2-1-67d1520d0ee8@chromium.org>
Date: Wed, 19 Nov 2025 20:17:36 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Hans de Goede <hansg@...nel.org>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans Verkuil <hverkuil@...nel.org>, Yunke Cao <yunkec@...gle.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 stable@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v2] media: uvcvideo: Fix support for
 V4L2_CTRL_FLAG_HAS_WHICH_MIN_MAX

The VIDIOC_G_EXT_CTRLS with which V4L2_CTRL_WHICH_(MIN|MAX)_VAL can only
work for controls that have previously announced support for it.

This patch fixes the following v4l2-compliance error:

  info: checking extended control 'User Controls' (0x00980001)
  fail: v4l2-test-controls.cpp(980): ret != EINVAL (got 13)
        test VIDIOC_G/S/TRY_EXT_CTRLS: FAIL

Fixes: 39d2c891c96e ("media: uvcvideo: support V4L2_CTRL_WHICH_MIN/MAX_VAL")
Cc: stable@...r.kernel.org
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
Changes in v2, Thanks Laurent:
- Remove redundant ioctl check
- CodeStyle
- Link to v1: https://lore.kernel.org/r/20251028-uvc-fix-which-v1-1-a7e6b82672a3@chromium.org
---
 drivers/media/usb/uvc/uvc_ctrl.c | 14 ++++++++++++--
 drivers/media/usb/uvc/uvc_v4l2.c | 10 ++++++----
 drivers/media/usb/uvc/uvcvideo.h |  2 +-
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 2905505c240c060e5034ea12d33b59d5702f2e1f..2738ef74c7373b185b67611da57610fd0b442080 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1432,7 +1432,7 @@ static bool uvc_ctrl_is_readable(u32 which, struct uvc_control *ctrl,
  * auto_exposure=1, exposure_time_absolute=251.
  */
 int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
-			   const struct v4l2_ext_controls *ctrls,
+			   const struct v4l2_ext_controls *ctrls, u32 which,
 			   unsigned long ioctl)
 {
 	struct uvc_control_mapping *master_map = NULL;
@@ -1442,14 +1442,24 @@ int uvc_ctrl_is_accessible(struct uvc_video_chain *chain, u32 v4l2_id,
 	s32 val;
 	int ret;
 	int i;
+	/*
+	 * There is no need to check the ioctl, all the ioctls except
+	 * VIDIOC_G_EXT_CTRLS use which=V4L2_CTRL_WHICH_CUR_VAL.
+	 */
+	bool is_which_min_max = which == V4L2_CTRL_WHICH_MIN_VAL ||
+				which == V4L2_CTRL_WHICH_MAX_VAL;
 
 	if (__uvc_query_v4l2_class(chain, v4l2_id, 0) >= 0)
-		return -EACCES;
+		return is_which_min_max ? -EINVAL : -EACCES;
 
 	ctrl = uvc_find_control(chain, v4l2_id, &mapping);
 	if (!ctrl)
 		return -EINVAL;
 
+	if ((!(ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN) ||
+	     !(ctrl->info.flags & UVC_CTRL_FLAG_GET_MAX)) && is_which_min_max)
+		return -EINVAL;
+
 	if (ioctl == VIDIOC_G_EXT_CTRLS)
 		return uvc_ctrl_is_readable(ctrls->which, ctrl, mapping);
 
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 9e4a251eca88085a1b4e0e854370015855be92ee..30c160daed8cb057b31ec00d665107dfdf4be1dc 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -765,14 +765,15 @@ static int uvc_ioctl_query_ext_ctrl(struct file *file, void *priv,
 
 static int uvc_ctrl_check_access(struct uvc_video_chain *chain,
 				 struct v4l2_ext_controls *ctrls,
-				 unsigned long ioctl)
+				 u32 which, unsigned long ioctl)
 {
 	struct v4l2_ext_control *ctrl = ctrls->controls;
 	unsigned int i;
 	int ret = 0;
 
 	for (i = 0; i < ctrls->count; ++ctrl, ++i) {
-		ret = uvc_ctrl_is_accessible(chain, ctrl->id, ctrls, ioctl);
+		ret = uvc_ctrl_is_accessible(chain, ctrl->id, ctrls, which,
+					     ioctl);
 		if (ret)
 			break;
 	}
@@ -806,7 +807,7 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *priv,
 		which = V4L2_CTRL_WHICH_CUR_VAL;
 	}
 
-	ret = uvc_ctrl_check_access(chain, ctrls, VIDIOC_G_EXT_CTRLS);
+	ret = uvc_ctrl_check_access(chain, ctrls, which, VIDIOC_G_EXT_CTRLS);
 	if (ret < 0)
 		return ret;
 
@@ -840,7 +841,8 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
 	if (!ctrls->count)
 		return 0;
 
-	ret = uvc_ctrl_check_access(chain, ctrls, ioctl);
+	ret = uvc_ctrl_check_access(chain, ctrls, V4L2_CTRL_WHICH_CUR_VAL,
+				    ioctl);
 	if (ret < 0)
 		return ret;
 
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index ed7bad31f75ca474c1037d666d5310c78dd764df..d583425893a5f716185153a07aae9bfe20182964 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -786,7 +786,7 @@ int uvc_ctrl_get(struct uvc_video_chain *chain, u32 which,
 		 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,
-			   const struct v4l2_ext_controls *ctrls,
+			   const struct v4l2_ext_controls *ctrls, u32 which,
 			   unsigned long ioctl);
 
 int uvc_xu_ctrl_query(struct uvc_video_chain *chain,

---
base-commit: c218ce4f98eccf5a40de64c559c52d61e9cc78ee
change-id: 20251028-uvc-fix-which-c3ba1fb68ed5

Best regards,
-- 
Ricardo Ribalda <ribalda@...omium.org>