[libcamera-devel] [PATCH 2/6] libcamera: v4l2_device: Add setControl function

[Jacopo Mondi]

Add function to set controls on a V4L2Device object.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
---
 src/libcamera/include/v4l2_device.h |  2 ++
 src/libcamera/v4l2_device.cpp       | 38 +++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
index c6f3d9a..2787847 100644
--- a/src/libcamera/include/v4l2_device.h
+++ b/src/libcamera/include/v4l2_device.h
@@ -51,6 +51,8 @@ public:
 	const char *deviceName() const { return caps_.card(); }
 	const char *busName() const { return caps_.bus_info(); }
 
+	int setControl(unsigned int control, int value);
+
 private:
 	std::string devnode_;
 	int fd_;
diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 59a1ad9..aef0996 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -195,4 +195,42 @@ void V4L2Device::close()
  * \return The string containing the device location
  */
 
+/**
+ * \brief Set a control value
+ * \param control The control identifier
+ * \param value The new control value
+ *
+ * Set a user control to the requested value. The function returns the
+ * new value actually assigned to the control, which might be different
+ * from the requested \a value one.
+ *
+ * \return The new control's value for success, or a negative error code otherwise
+ */
+int V4L2Device::setControl(unsigned int control, int value)
+{
+	struct v4l2_control v4l2_ctrl = {
+		.id = control,
+		.value = value,
+	};
+
+	int ret = ioctl(fd_, VIDIOC_S_CTRL, &v4l2_ctrl);
+	if (ret) {
+		ret = -errno;
+		LOG(Error) << "Failed to set control: " << strerror(-ret);
+		return ret;
+	}
+
+	v4l2_ctrl = { };
+	v4l2_ctrl.id = control;
+
+	ret = ioctl(fd_, VIDIOC_G_CTRL, &v4l2_ctrl);
+	if (ret) {
+		ret = -errno;
+		LOG(Error) << "Failed to get control: " << strerror(-ret);
+		return ret;
+	}
+
+	return v4l2_ctrl.value;
+}
+
 } /* namespace libcamera */
-- 
2.20.1