Base class for V4L2VideoDevice and V4L2Subdevice.
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Base class for V4L2VideoDevice and V4L2Subdevice.
The V4L2Device class groups together the methods and fields common to both the V4L2VideoDevice and V4L2Subdevice classes, and provides a base class with methods to open and close the device node associated with the device and to perform IOCTL system calls on it.
The V4L2Device class cannot be instantiated directly, as its constructor is protected. Users should instead create instances of one the derived classes to model either a V4L2 video device or a V4L2 subdevice.
◆ V4L2Device()
libcamera::V4L2Device::V4L2Device |
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const std::string & |
deviceNode | ) |
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protected |
Construct a V4L2Device.
- Parameters
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[in] | deviceNode | The device node filesystem path |
Initialize the file descriptor to -1 and store the deviceNode to be used at open() time, and the logTag to prefix log messages with.
◆ close()
void libcamera::V4L2Device::close |
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| ) |
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Close the device node.
Reset the file descriptor to -1
◆ controls()
libcamera::V4L2Device::controls |
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const |
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inline |
Retrieve the supported V4L2 controls and their information.
- Returns
- A map of the V4L2 controls supported by the device
◆ deviceNode()
libcamera::V4L2Device::deviceNode |
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const |
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inline |
Retrieve the device node path.
- Returns
- The device node path
◆ fd()
libcamera::V4L2Device::fd |
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inlineprotected |
Retrieve the V4L2 device file descriptor.
- Returns
- The V4L2 device file descriptor, -1 if the device node is not open
◆ getControls()
ControlList libcamera::V4L2Device::getControls |
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const std::vector< uint32_t > & |
ids | ) |
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Read controls from the device.
- Parameters
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[in] | ids | The list of controls to read, specified by their ID |
This method reads the value of all controls contained in ids, and returns their values as a ControlList.
If any control in ids is not supported by the device, is disabled (i.e. has the V4L2_CTRL_FLAG_DISABLED flag set), or if any other error occurs during validation of the requested controls, no control is read and this method returns an empty control list.
- Returns
- The control values in a ControlList on success, or an empty list on error
◆ ioctl()
int libcamera::V4L2Device::ioctl |
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unsigned long |
request, |
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void * |
argp |
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) |
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protected |
Perform an IOCTL system call on the device node.
- Parameters
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[in] | request | The IOCTL request code |
[in] | argp | A pointer to the IOCTL argument |
- Returns
- 0 on success or a negative error code otherwise
◆ isOpen()
libcamera::V4L2Device::isOpen |
( |
| ) |
const |
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inline |
Check if the V4L2 device node is open.
- Returns
- True if the V4L2 device node is open, false otherwise
◆ open()
int libcamera::V4L2Device::open |
( |
unsigned int |
flags | ) |
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protected |
Open a V4L2 device node.
- Parameters
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[in] | flags | Access mode flags |
Open the device node path with the provided access mode flags and initialize the file descriptor, which was initially set to -1.
- Returns
- 0 on success or a negative error code otherwise
◆ setControls()
int libcamera::V4L2Device::setControls |
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ControlList * |
ctrls | ) |
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Write controls to the device.
- Parameters
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[in] | ctrls | The list of controls to write |
This method writes the value of all controls contained in ctrls, and stores the values actually applied to the device in the corresponding ctrls entry.
If any control in ctrls is not supported by the device, is disabled (i.e. has the V4L2_CTRL_FLAG_DISABLED flag set), is read-only, if any other error occurs during validation of the requested controls, no control is written and this method returns -EINVAL.
If an error occurs while writing the controls, the index of the first control that couldn't be written is returned. All controls below that index are written and their values are updated in ctrls, while all other controls are not written and their values are not changed.
- Returns
- 0 on success or an error code otherwise
- Return values
-
-EINVAL | One of the control is not supported or not accessible |
i | The index of the control that failed |
◆ setFd()
int libcamera::V4L2Device::setFd |
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int |
fd | ) |
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protected |
Set the file descriptor of a V4L2 device.
- Parameters
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[in] | fd | The file descriptor handle |
This method allows a device to provide an already opened file descriptor referring to the V4L2 device node, instead of opening it with open(). This can be used for V4L2 M2M devices where a single video device node is used for both the output and capture devices, or when receiving an open file descriptor in a context that doesn't have permission to open the device node itself.
This method and the open() method are mutually exclusive, only one of the two shall be used for a V4L2Device instance.
- Returns
- 0 on success or a negative error code otherwise
The documentation for this class was generated from the following files:
- include/libcamera/internal/v4l2_device.h
- src/libcamera/v4l2_device.cpp