[PATCH v4 0/4] media: uvcvideo: live pan/tilt/zoom readback on OBSBOT Tiny 2 and Tail 2

[PATCH v4 0/4] media: uvcvideo: live pan/tilt/zoom readback on OBSBOT Tiny 2 and Tail 2

[Michael Jordan]

The OBSBOT Tiny 2 and Tail 2 do not set AUTOUPDATE in GET_INFO for their
pan/tilt and zoom controls, so uvcvideo returns cached values for them.
This series marks AUTO_UPDATE controls as volatile, applies the flags
fixup table to all controls, and adds entries for the two cameras.

Changes in v4:
- Shorten the commit messages (Laurent).
- Use "Assisted-by: LLM" (Ricardo).
- No code changes.

v3: https://lore.kernel.org/linux-media/20260928152416.766957-1-jordan.mymail@gmail.com/

Michael Jordan (4):
  media: uvcvideo: report AUTO_UPDATE controls as volatile
  media: uvcvideo: generalise the XU flags fixup to all controls
  media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tiny 2
  media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tail 2

 drivers/media/usb/uvc/uvc_ctrl.c | 126 +++++++++++++++++++++----------
 1 file changed, 85 insertions(+), 41 deletions(-)

-- 
2.43.0

[PATCH v4 1/4] media: uvcvideo: report AUTO_UPDATE controls as volatile

[Michael Jordan]

AUTO_UPDATE controls can change on their own, and the driver already
re-reads them from the device. Tell userspace by setting
V4L2_CTRL_FLAG_VOLATILE, plus EXECUTE_ON_WRITE for writable controls
so that writes are not ignored.

Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Assisted-by: LLM
Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 3ca108b83f1d..aceb263103e9 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1840,6 +1840,17 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
 	if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_MAX) &&
 	    (ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN))
 		v4l2_ctrl->flags |= V4L2_CTRL_FLAG_HAS_WHICH_MIN_MAX;
+	if (ctrl->info.flags & UVC_CTRL_FLAG_AUTO_UPDATE) {
+		v4l2_ctrl->flags |= V4L2_CTRL_FLAG_VOLATILE;
+		/*
+		 * Writes to a volatile control are documented to be ignored
+		 * unless EXECUTE_ON_WRITE is also reported. The driver sends
+		 * every write of a writable control to the device, so report
+		 * the flag accordingly.
+		 */
+		if (ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR)
+			v4l2_ctrl->flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
+	}
 
 	if (mapping->master_id)
 		__uvc_find_control(ctrl->entity, mapping->master_id,
-- 
2.43.0

Re: [PATCH v4 1/4] media: uvcvideo: report AUTO_UPDATE controls as volatile

[Laurent Pinchart]

On Mon, Sep 28, 2026 at 05:50:18PM -0400, Michael Jordan wrote:
> AUTO_UPDATE controls can change on their own, and the driver already
> re-reads them from the device. Tell userspace by setting
> V4L2_CTRL_FLAG_VOLATILE, plus EXECUTE_ON_WRITE for writable controls
> so that writes are not ignored.

Writes are not ignored by the driver regardless of whether or not
V4L2_CTRL_FLAG_EXECUTE_ON_WRITE is reported to userspace.

> Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
> Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
> Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
> Assisted-by: LLM
> Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 3ca108b83f1d..aceb263103e9 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1840,6 +1840,17 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>  	if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_MAX) &&
>  	    (ctrl->info.flags & UVC_CTRL_FLAG_GET_MIN))
>  		v4l2_ctrl->flags |= V4L2_CTRL_FLAG_HAS_WHICH_MIN_MAX;

A blank line here would be nice.

> +	if (ctrl->info.flags & UVC_CTRL_FLAG_AUTO_UPDATE) {
> +		v4l2_ctrl->flags |= V4L2_CTRL_FLAG_VOLATILE;
> +		/*
> +		 * Writes to a volatile control are documented to be ignored
> +		 * unless EXECUTE_ON_WRITE is also reported. The driver sends
> +		 * every write of a writable control to the device, so report
> +		 * the flag accordingly.
> +		 */
> +		if (ctrl->info.flags & UVC_CTRL_FLAG_SET_CUR)
> +			v4l2_ctrl->flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
> +	}

The V4L2 documentation also states

  Setting a new value for a volatile control will never trigger a
  V4L2_EVENT_CTRL_CH_VALUE event.

This patch seems to break that as we unconditionally send
V4L2_EVENT_CTRL_CH_VALUE events on control write for controls that don't
have UVC_CTRL_FLAG_ASYNCHRONOUS set.

>  
>  	if (mapping->master_id)
>  		__uvc_find_control(ctrl->entity, mapping->master_id,

-- 
Regards,

Laurent Pinchart

Re: [PATCH v4 1/4] media: uvcvideo: report AUTO_UPDATE controls as volatile

[Michael Jordan]

Hi Laurent,

You're right. The driver already sends the writes regardless of
EXECUTE_ON_WRITE. I'll correct the commit message and add the blank
line.

I also missed the restriction on write-triggered CH_VALUE events.
Reporting VOLATILE needs corresponding changes to the event handling.
I'll check the write-notification paths, including asynchronous
completion, and test those changes before sending v5.

Thanks,
Michael

[PATCH v4 2/4] media: uvcvideo: generalise the XU flags fixup to all controls

[Michael Jordan]

The flags fixup table is only applied to extension unit controls.
Apply it to all controls, and skip GET_INFO when an entry matches.

Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Assisted-by: LLM
Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
---
 drivers/media/usb/uvc/uvc_ctrl.c | 91 ++++++++++++++++++--------------
 1 file changed, 50 insertions(+), 41 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index aceb263103e9..64c90c380d3d 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2852,6 +2852,48 @@ int uvc_ctrl_set(struct uvc_fh *handle, struct v4l2_ext_control *xctrl)
  * Dynamic controls
  */
 
+static bool uvc_ctrl_fixup_flags(struct uvc_device *dev,
+				 const struct uvc_control *ctrl,
+				 struct uvc_control_info *info)
+{
+	struct uvc_ctrl_fixup {
+		struct usb_device_id id;
+		u8 entity;
+		u8 selector;
+		u8 flags;
+	};
+
+	static const struct uvc_ctrl_fixup fixups[] = {
+		{ { USB_DEVICE(0x046d, 0x08c2) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x046d, 0x08cc) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x046d, 0x0994) }, 9, 1,
+			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
+			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+	};
+
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(fixups); ++i) {
+		if (!usb_match_one_id(dev->intf, &fixups[i].id))
+			continue;
+
+		if (fixups[i].entity == ctrl->entity->id &&
+		    fixups[i].selector == info->selector) {
+			info->flags = fixups[i].flags;
+			return true;
+		}
+	}
+
+	return false;
+}
+
 /*
  * Retrieve flags for a given control
  */
@@ -2862,6 +2904,14 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
 	u8 *data;
 	int ret;
 
+	/*
+	 * Some devices report bogus capabilities through GET_INFO. If the
+	 * fixup table covers this control, take the flags from the table and
+	 * skip the query altogether.
+	 */
+	if (uvc_ctrl_fixup_flags(dev, ctrl, info))
+		return 0;
+
 	data = kmalloc(1, GFP_KERNEL);
 	if (data == NULL)
 		return -ENOMEM;
@@ -2893,45 +2943,6 @@ static int uvc_ctrl_get_flags(struct uvc_device *dev,
 	return ret;
 }
 
-static void uvc_ctrl_fixup_xu_info(struct uvc_device *dev,
-	const struct uvc_control *ctrl, struct uvc_control_info *info)
-{
-	struct uvc_ctrl_fixup {
-		struct usb_device_id id;
-		u8 entity;
-		u8 selector;
-		u8 flags;
-	};
-
-	static const struct uvc_ctrl_fixup fixups[] = {
-		{ { USB_DEVICE(0x046d, 0x08c2) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-		{ { USB_DEVICE(0x046d, 0x08cc) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-		{ { USB_DEVICE(0x046d, 0x0994) }, 9, 1,
-			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
-			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
-			UVC_CTRL_FLAG_AUTO_UPDATE },
-	};
-
-	unsigned int i;
-
-	for (i = 0; i < ARRAY_SIZE(fixups); ++i) {
-		if (!usb_match_one_id(dev->intf, &fixups[i].id))
-			continue;
-
-		if (fixups[i].entity == ctrl->entity->id &&
-		    fixups[i].selector == info->selector) {
-			info->flags = fixups[i].flags;
-			return;
-		}
-	}
-}
-
 /*
  * Query control information (size and flags) for XU controls.
  */
@@ -2972,8 +2983,6 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,
 		goto done;
 	}
 
-	uvc_ctrl_fixup_xu_info(dev, ctrl, info);
-
 	uvc_dbg(dev, CONTROL,
 		"XU control %pUl/%u queried: len %u, flags { get %u set %u auto %u }\n",
 		info->entity, info->selector, info->size,
-- 
2.43.0

[PATCH v4 3/4] media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tiny 2

[Michael Jordan]

The OBSBOT Tiny 2 does not set AUTOUPDATE in GET_INFO for its pan/tilt
and zoom controls, so reads return the last value written. The camera
moves them on its own when tracking a subject, and sends no control
change events.

Add fixup entries for the three controls.

lsusb -v (device descriptor and Camera Terminal):

  Bus 003 Device 006: ID 3564:fef8 Remo Tech Co., Ltd. OBSBOT Tiny 2
  Device Descriptor:
    bLength                18
    bDescriptorType         1
    bcdUSB               2.10
    bDeviceClass          239 Miscellaneous Device
    bDeviceSubClass         2 [unknown]
    bDeviceProtocol         1 Interface Association
    bMaxPacketSize0        64
    idVendor           0x3564 Remo Tech Co., Ltd.
    idProduct          0xfef8 OBSBOT Tiny 2
    bcdDevice            4.09
    iManufacturer           1 Remo Tech Co., Ltd.
    iProduct                2 OBSBOT Tiny 2
    iSerial                 0
    bNumConfigurations      1
  [...]
      VideoControl Interface Descriptor:
        bLength                18
        bDescriptorType        36
        bDescriptorSubtype      2 (INPUT_TERMINAL)
        bTerminalID             1
        wTerminalType      0x0201 Camera Sensor
        bAssocTerminal          0
        iTerminal               0
        wObjectiveFocalLengthMin      0
        wObjectiveFocalLengthMax      0
        wOcularFocalLength            0
        bControlSize                  3
        bmControls           0x00023e3e
          Auto-Exposure Mode
          Auto-Exposure Priority
          Exposure Time (Absolute)
          Exposure Time (Relative)
          Focus (Absolute)
          Zoom (Absolute)
          Zoom (Relative)
          PanTilt (Absolute)
          PanTilt (Relative)
          Roll (Absolute)
          Focus, Auto

Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Assisted-by: LLM
Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
---
 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 64c90c380d3d..49ea6a6bcf57 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2876,6 +2876,18 @@ static bool uvc_ctrl_fixup_flags(struct uvc_device *dev,
 			UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX |
 			UVC_CTRL_FLAG_GET_DEF | UVC_CTRL_FLAG_SET_CUR |
 			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfef8) }, 1,
+			UVC_CT_PANTILT_ABSOLUTE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_RESTORE | UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfef8) }, 1,
+			UVC_CT_PANTILT_RELATIVE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfef8) }, 1,
+			UVC_CT_ZOOM_ABSOLUTE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_RESTORE | UVC_CTRL_FLAG_AUTO_UPDATE },
 	};
 
 	unsigned int i;
-- 
2.43.0

[PATCH v4 4/4] media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tail 2

[Michael Jordan]

The OBSBOT Tail 2 has the same defect as the Tiny 2. Add the same
fixup entries for it.

lsusb -v (device descriptor and Camera Terminal):

  Bus 002 Device 003: ID 3564:fefc Remo Tech Co., Ltd. OBSBOT Tail 2
  Device Descriptor:
    bLength                18
    bDescriptorType         1
    bcdUSB               3.20
    bDeviceClass          239 Miscellaneous Device
    bDeviceSubClass         2 [unknown]
    bDeviceProtocol         1 Interface Association
    bMaxPacketSize0         9
    idVendor           0x3564 Remo Tech Co., Ltd.
    idProduct          0xfefc OBSBOT Tail 2
    bcdDevice            4.19
    iManufacturer           1 Remo Tech Co., Ltd.
    iProduct                2 OBSBOT Tail 2
    iSerial                 0
    bNumConfigurations      1
  [...]
      VideoControl Interface Descriptor:
        bLength                18
        bDescriptorType        36
        bDescriptorSubtype      2 (INPUT_TERMINAL)
        bTerminalID             1
        wTerminalType      0x0201 Camera Sensor
        bAssocTerminal          0
        iTerminal               0
        wObjectiveFocalLengthMin      0
        wObjectiveFocalLengthMax      0
        wOcularFocalLength            0
        bControlSize                  3
        bmControls           0x00023e3e
          Auto-Exposure Mode
          Auto-Exposure Priority
          Exposure Time (Absolute)
          Exposure Time (Relative)
          Focus (Absolute)
          Zoom (Absolute)
          Zoom (Relative)
          PanTilt (Absolute)
          PanTilt (Relative)
          Roll (Absolute)
          Focus, Auto

Assisted-by: LLM
Signed-off-by: Michael Jordan <jordan.mymail@gmail.com>
---
 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 49ea6a6bcf57..202c2c95432a 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2888,6 +2888,18 @@ static bool uvc_ctrl_fixup_flags(struct uvc_device *dev,
 			UVC_CT_ZOOM_ABSOLUTE_CONTROL,
 			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
 			UVC_CTRL_FLAG_RESTORE | UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfefc) }, 1,
+			UVC_CT_PANTILT_ABSOLUTE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_RESTORE | UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfefc) }, 1,
+			UVC_CT_PANTILT_RELATIVE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_AUTO_UPDATE },
+		{ { USB_DEVICE(0x3564, 0xfefc) }, 1,
+			UVC_CT_ZOOM_ABSOLUTE_CONTROL,
+			UVC_CTRL_FLAG_SET_CUR | UVC_CTRL_FLAG_GET_RANGE |
+			UVC_CTRL_FLAG_RESTORE | UVC_CTRL_FLAG_AUTO_UPDATE },
 	};
 
 	unsigned int i;
-- 
2.43.0

Re: [PATCH v4 0/4] media: uvcvideo: live pan/tilt/zoom readback on OBSBOT Tiny 2 and Tail 2

[Hans de Goede]

Hi,

On 28-Sep-26 23:50, Michael Jordan wrote:
> The OBSBOT Tiny 2 and Tail 2 do not set AUTOUPDATE in GET_INFO for their
> pan/tilt and zoom controls, so uvcvideo returns cached values for them.
> This series marks AUTO_UPDATE controls as volatile, applies the flags
> fixup table to all controls, and adds entries for the two cameras.
> 
> Changes in v4:
> - Shorten the commit messages (Laurent).
> - Use "Assisted-by: LLM" (Ricardo).
> - No code changes.

Thank you for your patch.

I have merged patches 2-4 into:

https://gitlab.freedesktop.org/linux-media/users/uvc/-/commits/for-next/

For patch 1/4 lets wait for a new version and see if Laurent likes
that better.

Regards,

Hans



> 
> v3: https://lore.kernel.org/linux-media/20260928152416.766957-1-jordan.mymail@gmail.com/
> 
> Michael Jordan (4):
>   media: uvcvideo: report AUTO_UPDATE controls as volatile
>   media: uvcvideo: generalise the XU flags fixup to all controls
>   media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tiny 2
>   media: uvcvideo: fix up missing AUTO_UPDATE on the OBSBOT Tail 2
> 
>  drivers/media/usb/uvc/uvc_ctrl.c | 126 +++++++++++++++++++++----------
>  1 file changed, 85 insertions(+), 41 deletions(-)
>