[libcamera-devel] [RFC] libcamera: v4l2_device: Update control info

[Jacopo Mondi]

Setting controls on a V4L2 device might update the limits of other
related controls (in example, setting a new vertical/horizontal blanking
value might modify the available exposure time duration).

Add a funtion to update the ControlInfo that represents a control
minimum, maximum and default values and call it after a new control has
been set and format is changed on a V4L2 subdevice.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---

We'll soon need something like that.
However, seems like an expensive operation to perform after every control
and format update.

Opinions ?

---
 include/libcamera/controls.h             |  4 ++
 include/libcamera/internal/v4l2_device.h |  2 +
 src/libcamera/controls.cpp               | 18 +++++++++
 src/libcamera/v4l2_device.cpp            | 48 ++++++++++++++++++++++++
 src/libcamera/v4l2_subdevice.cpp         |  3 ++
 5 files changed, 75 insertions(+)

diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
index 80944efc133a..74b0c6b26517 100644
--- a/include/libcamera/controls.h
+++ b/include/libcamera/controls.h
@@ -273,6 +273,10 @@ public:
 	const ControlValue &max() const { return max_; }
 	const ControlValue &def() const { return def_; }

+	void setMin(ControlValue val) { min_ = val; }
+	void setMax(ControlValue val) { max_ = val; }
+	void setDef(ControlValue val) { def_ = val; }
+
 	std::string toString() const;

 	bool operator==(const ControlInfo &other) const
diff --git a/include/libcamera/internal/v4l2_device.h b/include/libcamera/internal/v4l2_device.h
index d491eafd262e..1563ec7272c7 100644
--- a/include/libcamera/internal/v4l2_device.h
+++ b/include/libcamera/internal/v4l2_device.h
@@ -42,6 +42,8 @@ protected:

 	int fd() { return fd_; }

+	void updateControlsInfo();
+
 private:
 	void listControls();
 	void updateControls(ControlList *ctrls,
diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
index dca782667d88..f92128dd1878 100644
--- a/src/libcamera/controls.cpp
+++ b/src/libcamera/controls.cpp
@@ -519,6 +519,24 @@ ControlInfo::ControlInfo(const ControlValue &min,
  * \return A ControlValue with the default value for the control
  */

+/**
+ * \fn ControlInfo::setMin()
+ * \brief Set the minimum value for the control
+ * \param[in] val The control minimum value
+ */
+
+/**
+ * \fn ControlInfo::setMax()
+ * \brief Set the maximum value for the control
+ * \param[in] val The control maximum value
+ */
+
+/**
+ * \fn ControlInfo::setDef()
+ * \brief Set the default value for the control
+ * \param[in] val The control default value
+ */
+
 /**
  * \brief Provide a string representation of the ControlInfo
  */
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 56ea1ddda2c1..7e1286d7ddd0 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -346,6 +346,7 @@ int V4L2Device::setControls(ControlList *ctrls)
 	}

 	updateControls(ctrls, v4l2Ctrls, count);
+	updateControlsInfo();

 	return ret;
 }
@@ -380,6 +381,53 @@ int V4L2Device::ioctl(unsigned long request, void *argp)
  * \return The V4L2 device file descriptor, -1 if the device node is not open
  */

+/**
+ * \brief Update the control info
+ *
+ * Update all control limits (min and max) and default value.
+ */
+void V4L2Device::updateControlsInfo()
+{
+	for (auto &it : controls_) {
+		const ControlId *id = it.first;
+		ControlInfo &info = it.second;
+		struct v4l2_query_ext_ctrl ctrl = {};
+		ctrl.id = id->id();
+		int ret = ioctl(VIDIOC_QUERY_EXT_CTRL, &ctrl);
+		if (ret) {
+			LOG(V4L2, Error) << "Unable to query control "
+					 << ctrl.id << ": " << strerror(-ret);
+			return;
+		}
+
+		switch (ctrl.type) {
+		case V4L2_CTRL_TYPE_U8:
+			info.setMin({ static_cast<uint8_t>(ctrl.minimum) });
+			info.setMax({ static_cast<uint8_t>(ctrl.maximum) });
+			info.setDef({ static_cast<uint8_t>(ctrl.default_value) });
+			break;
+
+		case V4L2_CTRL_TYPE_BOOLEAN:
+			info.setMin({ static_cast<bool>(ctrl.minimum) });
+			info.setMax({ static_cast<bool>(ctrl.maximum) });
+			info.setDef({ static_cast<bool>(ctrl.default_value) });
+			break;
+
+		case V4L2_CTRL_TYPE_INTEGER64:
+			info.setMin({ static_cast<bool>(ctrl.minimum) });
+			info.setMax({ static_cast<bool>(ctrl.maximum) });
+			info.setDef({ static_cast<bool>(ctrl.default_value) });
+			break;
+
+		default:
+			info.setMin({ static_cast<bool>(ctrl.minimum) });
+			info.setMax({ static_cast<bool>(ctrl.maximum) });
+			info.setDef({ static_cast<bool>(ctrl.default_value) });
+			break;
+		}
+	}
+}
+
 /*
  * \brief List and store information about all controls supported by the
  * V4L2 device
diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
index 7aefc1be032d..c0dc036a09cc 100644
--- a/src/libcamera/v4l2_subdevice.cpp
+++ b/src/libcamera/v4l2_subdevice.cpp
@@ -411,6 +411,9 @@ int V4L2Subdevice::setFormat(unsigned int pad, V4L2SubdeviceFormat *format,
 	format->size.height = subdevFmt.format.height;
 	format->mbus_code = subdevFmt.format.code;

+	/* Changing the format could update the contol limits. */
+	updateControlsInfo();
+
 	return 0;
 }

--
2.27.0