Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst

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Linux kernel
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Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
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.rst
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8210 bytes
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232
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _flash-controls:

***********************
Flash Control Reference
***********************

The V4L2 flash controls are intended to provide generic access to flash
controller devices. Flash controller devices are typically used in
digital cameras.

The interface can support both LED and xenon flash devices. As of
writing this, there is no xenon flash driver using this interface.


.. _flash-controls-use-cases:

Supported use cases
===================


Unsynchronised LED flash (software strobe)
------------------------------------------

Unsynchronised LED flash is controlled directly by the host as the
sensor. The flash must be enabled by the host before the exposure of the
image starts and disabled once it ends. The host is fully responsible
for the timing of the flash.

Example of such device: Nokia N900.


Synchronised LED flash (hardware strobe)
----------------------------------------

The synchronised LED flash is pre-programmed by the host (power and
timeout) but controlled by the sensor through a strobe signal from the
sensor to the flash.

The sensor controls the flash duration and timing. This information
typically must be made available to the sensor.


LED flash as torch
------------------

LED flash may be used as torch in conjunction with another use case
involving camera or individually.


.. _flash-control-id:

Flash Control IDs
-----------------

``V4L2_CID_FLASH_CLASS (class)``
    The FLASH class descriptor.

.. _v4l2-cid-flash-led-mode:

``V4L2_CID_FLASH_LED_MODE (menu)``
    Defines the mode of the flash LED, the high-power white LED attached
    to the flash controller. Setting this control may not be possible in
    presence of some faults. See V4L2_CID_FLASH_FAULT.


.. tabularcolumns:: |p{5.7cm}|p{11.8cm}|

Annotation

Implementation Notes