[libcamera-devel] [PATCH v5 3/6] libcamera: v4l2_device: Implement get and set controls

[Jacopo Mondi]

Implement getControls() and setControls() operations in V4L2Device class.

Both operations take a V4L2Controls instance and read or write the V4L2
controls on the V4L2 device.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/libcamera/include/v4l2_device.h |   3 +
 src/libcamera/v4l2_device.cpp       | 193 ++++++++++++++++++++++++++++
 2 files changed, 196 insertions(+)

diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
index 91a72fcecbcc..3af27c9f7af5 100644
--- a/src/libcamera/include/v4l2_device.h
+++ b/src/libcamera/include/v4l2_device.h
@@ -15,6 +15,7 @@
 namespace libcamera {
 
 class V4L2ControlInfo;
+class V4L2Controls;
 
 class V4L2Device : protected Loggable
 {
@@ -23,6 +24,8 @@ public:
 	bool isOpen() const { return fd_ != -1; }
 
 	const V4L2ControlInfo *getControlInfo(unsigned int id) const;
+	int getControls(V4L2Controls *ctrls);
+	int setControls(V4L2Controls *ctrls);
 
 	const std::string &deviceNode() const { return deviceNode_; }
 
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index b113ff77e3cf..efe30ef856ae 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -125,6 +125,199 @@ const V4L2ControlInfo *V4L2Device::getControlInfo(unsigned int id) const
 	return &it->second;
 }
 
+/**
+ * \brief Read controls from the device
+ * \param[inout] ctrls The list of controls to read
+ *
+ * Read the value of each control contained in \a ctrls, and store the
+ * value in the corresponding \a ctrls entry.
+ *
+ * If an integer number less than the requested number of controls is returned,
+ * only controls up to that index have been successfully read.
+ *
+ * Each V4L2Control instance in \a ctrls should be supported by the device and
+ * accessible (ie the V4L2_CTRL_FLAG_DISABLED flag should not be set), otherwise
+ * a negative error code (-EINVAL) is returned
+ *
+ * \return 0 on success or an error code otherwise
+ * \retval -EINVAL One of the control is not supported or not accessible
+ * \retval i The index of the control that failed
+ */
+int V4L2Device::getControls(V4L2Controls *ctrls)
+{
+	unsigned int count = ctrls->size();
+	if (count == 0)
+		return 0;
+
+	const V4L2ControlInfo *controlInfo[count] = {};
+	struct v4l2_ext_control v4l2Ctrls[count] = {};
+
+	for (unsigned int i = 0; i < count; ++i) {
+		V4L2Control *ctrl = (*ctrls)[i];
+
+		const V4L2ControlInfo *info = getControlInfo(ctrl->id());
+		if (!info) {
+			LOG(V4L2, Error)
+				<< "Control '" << ctrl->id() << "' not found";
+			return -EINVAL;
+		}
+
+		controlInfo[i] = info;
+		v4l2Ctrls[i].id = info->id();
+	}
+
+	struct v4l2_ext_controls v4l2ExtCtrls = {};
+	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
+	v4l2ExtCtrls.controls = v4l2Ctrls;
+	v4l2ExtCtrls.count = count;
+
+	int ret = ioctl(VIDIOC_G_EXT_CTRLS, &v4l2ExtCtrls);
+	if (ret) {
+		unsigned int errorIdx = v4l2ExtCtrls.error_idx;
+
+		/* Generic validation error. */
+		if (errorIdx == count) {
+			LOG(V4L2, Error) << "Unable to read controls: "
+					 << strerror(ret);
+			return -EINVAL;
+		}
+
+		/* A specific control failed. */
+		LOG(V4L2, Error) << "Unable to read control " << errorIdx
+				 << ": " << strerror(ret);
+		return errorIdx;
+	}
+
+	/*
+	 * For each control read from the device, set the value in the
+	 * V4L2Control provided by the caller.
+	 */
+	for (unsigned int i = 0; i < count; ++i) {
+		struct v4l2_ext_control *v4l2Ctrl = &v4l2Ctrls[i];
+		const V4L2ControlInfo *info = controlInfo[i];
+		V4L2Control *ctrl = (*ctrls)[i];
+
+		switch (info->type()) {
+		case V4L2_CTRL_TYPE_INTEGER64:
+			ctrl->setValue(v4l2Ctrl->value64);
+			break;
+		default:
+			/*
+			 * \todo To be changed when support for string and
+			 * compound controls will be added.
+			 */
+			ctrl->setValue(static_cast<long int>(v4l2Ctrl->value));
+			break;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * \brief Write controls to the device
+ * \param[in] ctrls The list of controls to write
+ *
+ * Write the value of each V4L2Control contained in \a ctrls. Each
+ * control should be initialized by the caller with a value, otherwise
+ * the result of the operation is undefined.
+ *
+ * The value of each control is updated to reflect what has been
+ * actually applied on the device.
+ *
+ * If an integer number less than the requested number of controls is returned,
+ * only controls up to that index have been successfully applied.
+ *
+ * Each V4L2Control instance in \a ctrls should be supported by the device and
+ * accessible (ie the V4L2_CTRL_FLAG_DISABLED flag should not be set), otherwise
+ * a negative error code (-EINVAL) is returned
+ *
+ * \return 0 on success or an error code otherwise
+ * \retval -EINVAL One of the control is not supported or not accessible
+ * \retval i The index of the control that failed
+ */
+int V4L2Device::setControls(V4L2Controls *ctrls)
+{
+	unsigned int count = ctrls->size();
+	if (count == 0)
+		return 0;
+
+	const V4L2ControlInfo *controlInfo[count] = {};
+	struct v4l2_ext_control v4l2Ctrls[count] = {};
+
+	for (unsigned int i = 0; i < count; ++i) {
+		V4L2Control *ctrl = (*ctrls)[i];
+
+		const V4L2ControlInfo *info = getControlInfo(ctrl->id());
+		if (!info) {
+			LOG(V4L2, Error)
+				<< "Control '" << ctrl->id() << "' not found";
+			return -EINVAL;
+		}
+
+		controlInfo[i] = info;
+		v4l2Ctrls[i].id = info->id();
+
+		/* Set the v4l2_ext_control value for the write operation. */
+		switch (info->type()) {
+		case V4L2_CTRL_TYPE_INTEGER64:
+			v4l2Ctrls[i].value64 = ctrl->value();
+			break;
+		default:
+			/*
+			 * \todo To be changed when support for string and
+			 * compound controls will be added.
+			 */
+			v4l2Ctrls[i].value = static_cast<int32_t>(ctrl->value());
+			break;
+		}
+	}
+
+	struct v4l2_ext_controls v4l2ExtCtrls = {};
+	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
+	v4l2ExtCtrls.controls = v4l2Ctrls;
+	v4l2ExtCtrls.count = count;
+
+	int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
+	if (ret) {
+		unsigned int errorIdx = v4l2ExtCtrls.error_idx;
+
+		/* Generic validation error. */
+		if (errorIdx == count) {
+			LOG(V4L2, Error) << "Unable to read controls: "
+					 << strerror(ret);
+			return -EINVAL;
+		}
+
+		/* A specific control failed. */
+		LOG(V4L2, Error) << "Unable to read control " << errorIdx
+				 << ": " << strerror(ret);
+		return errorIdx;
+	}
+
+	/* Update the control value to what have actually been applied. */
+	for (unsigned int i = 0; i < count; ++i) {
+		struct v4l2_ext_control *v4l2Ctrl = &v4l2Ctrls[i];
+		const V4L2ControlInfo *info = controlInfo[i];
+		V4L2Control *ctrl = (*ctrls)[i];
+
+		switch (info->type()) {
+		case V4L2_CTRL_TYPE_INTEGER64:
+			ctrl->setValue(v4l2Ctrl->value64);
+			break;
+		default:
+			/*
+			 * \todo To be changed when support for string and
+			 * compound controls will be added.
+			 */
+			ctrl->setValue(static_cast<long int>(v4l2Ctrl->value));
+			break;
+		}
+	}
+
+	return 0;
+}
+
 /**
  * \brief Perform an IOCTL system call on the device node
  * \param[in] request The IOCTL request code
-- 
2.21.0