[v3,09/11] v4l2: Allow probing optional selection rectangles
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Message ID 20261016202818.1405645-10-halfline@gmail.com
State New
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Series
  • software-isp: Align crops, statistics and metadata
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Commit Message

Ray Strode Oct. 16, 2026, 8:28 p.m. UTC 
From: Ray Strode <rstrode@redhat.com>

This commit allows callers to query optional subdevice selections without
logging an error when the API or target is unsupported.

Determining the sensor region captured by a pipeline requires checking
whether its intermediate subdevices crop or compose the image. The
selection ioctl or a particular target may be absent on a pass-through
device, and that expected result currently produces an error message.

Signed-off-by: Ray Strode <rstrode@redhat.com>
---
 include/libcamera/internal/v4l2_subdevice.h |  7 ++++---
 src/libcamera/v4l2_subdevice.cpp            | 12 ++++++++++--
 2 files changed, 14 insertions(+), 5 deletions(-)

Patch
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diff --git a/include/libcamera/internal/v4l2_subdevice.h b/include/libcamera/internal/v4l2_subdevice.h
index c37a82af..41dc80f2 100644
--- a/include/libcamera/internal/v4l2_subdevice.h
+++ b/include/libcamera/internal/v4l2_subdevice.h
@@ -123,10 +123,11 @@  public:
 	const MediaEntity *entity() const { return entity_; }
 
 	int getSelection(const Stream &stream, unsigned int target,
-			 Rectangle *rect);
-	int getSelection(unsigned int pad, unsigned int target, Rectangle *rect)
+			 Rectangle *rect, bool optional = false);
+	int getSelection(unsigned int pad, unsigned int target, Rectangle *rect,
+			 bool optional = false)
 	{
-		return getSelection({ pad, 0 }, target, rect);
+		return getSelection({ pad, 0 }, target, rect, optional);
 	}
 	int setSelection(const Stream &stream, unsigned int target,
 			 Rectangle *rect);
diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
index a69de154..2e23f9ad 100644
--- a/src/libcamera/v4l2_subdevice.cpp
+++ b/src/libcamera/v4l2_subdevice.cpp
@@ -1171,13 +1171,17 @@  int V4L2Subdevice::open()
  * \param[in] stream The stream the rectangle is retrieved from
  * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
  * \param[out] rect The retrieved selection rectangle
+ * \param[in] optional Whether unsupported targets are expected
+ *
+ * Optional queries return -ENOTTY or -EINVAL without logging an error when
+ * the selection API or target is unsupported. Other errors are logged normally.
  *
  * \todo Define a V4L2SelectionTarget enum for the selection target
  *
  * \return 0 on success or a negative error code otherwise
  */
 int V4L2Subdevice::getSelection(const Stream &stream, unsigned int target,
-				Rectangle *rect)
+				Rectangle *rect, bool optional)
 {
 	struct v4l2_subdev_selection sel = {};
 
@@ -1189,6 +1193,9 @@  int V4L2Subdevice::getSelection(const Stream &stream, unsigned int target,
 
 	int ret = ioctl(VIDIOC_SUBDEV_G_SELECTION, &sel);
 	if (ret < 0) {
+		if (optional && (ret == -ENOTTY || ret == -EINVAL))
+			return ret;
+
 		LOG(V4L2, Error)
 			<< "Unable to get rectangle " << target << " on pad "
 			<< stream << ": " << strerror(-ret);
@@ -1205,11 +1212,12 @@  int V4L2Subdevice::getSelection(const Stream &stream, unsigned int target,
 
 /**
  * \fn V4L2Subdevice::getSelection(unsigned int pad, unsigned int target,
- * Rectangle *rect)
+ * Rectangle *rect, bool optional)
  * \brief Get selection rectangle \a rect for \a target
  * \param[in] pad The 0-indexed pad number the rectangle is retrieved from
  * \param[in] target The selection target defined by the V4L2_SEL_TGT_* flags
  * \param[out] rect The retrieved selection rectangle
+ * \param[in] optional Whether unsupported targets are expected
  *
  * \return 0 on success or a negative error code otherwise
  */