| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| |
| .. _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 (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. |
| |
| |
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| * - ``V4L2_FLASH_LED_MODE_NONE`` |
| - Off. |
| * - ``V4L2_FLASH_LED_MODE_FLASH`` |
| - Flash mode. |
| * - ``V4L2_FLASH_LED_MODE_TORCH`` |
| - Torch mode. |
| |
| See V4L2_CID_FLASH_TORCH_INTENSITY. |
| |
| |
| |
| ``V4L2_CID_FLASH_STROBE_SOURCE (menu)`` |
| Defines the source of the flash LED strobe. |
| |
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| * - ``V4L2_FLASH_STROBE_SOURCE_SOFTWARE`` |
| - The flash strobe is triggered by using the |
| V4L2_CID_FLASH_STROBE control. |
| * - ``V4L2_FLASH_STROBE_SOURCE_EXTERNAL`` |
| - The flash strobe is triggered by an external source. Typically |
| this is a sensor, which makes it possible to synchronise the |
| flash strobe start to exposure start. |
| |
| |
| |
| ``V4L2_CID_FLASH_STROBE (button)`` |
| Strobe flash. Valid when V4L2_CID_FLASH_LED_MODE is set to |
| V4L2_FLASH_LED_MODE_FLASH and V4L2_CID_FLASH_STROBE_SOURCE |
| is set to V4L2_FLASH_STROBE_SOURCE_SOFTWARE. Setting this |
| control may not be possible in presence of some faults. See |
| V4L2_CID_FLASH_FAULT. |
| |
| ``V4L2_CID_FLASH_STROBE_STOP (button)`` |
| Stop flash strobe immediately. |
| |
| ``V4L2_CID_FLASH_STROBE_STATUS (boolean)`` |
| Strobe status: whether the flash is strobing at the moment or not. |
| This is a read-only control. |
| |
| ``V4L2_CID_FLASH_TIMEOUT (integer)`` |
| Hardware timeout for flash. The flash strobe is stopped after this |
| period of time has passed from the start of the strobe. |
| |
| ``V4L2_CID_FLASH_INTENSITY (integer)`` |
| Intensity of the flash strobe when the flash LED is in flash mode |
| (V4L2_FLASH_LED_MODE_FLASH). The unit should be milliamps (mA) |
| if possible. |
| |
| ``V4L2_CID_FLASH_TORCH_INTENSITY (integer)`` |
| Intensity of the flash LED in torch mode |
| (V4L2_FLASH_LED_MODE_TORCH). The unit should be milliamps (mA) |
| if possible. Setting this control may not be possible in presence of |
| some faults. See V4L2_CID_FLASH_FAULT. |
| |
| ``V4L2_CID_FLASH_INDICATOR_INTENSITY (integer)`` |
| Intensity of the indicator LED. The indicator LED may be fully |
| independent of the flash LED. The unit should be microamps (uA) if |
| possible. |
| |
| ``V4L2_CID_FLASH_FAULT (bitmask)`` |
| Faults related to the flash. The faults tell about specific problems |
| in the flash chip itself or the LEDs attached to it. Faults may |
| prevent further use of some of the flash controls. In particular, |
| V4L2_CID_FLASH_LED_MODE is set to V4L2_FLASH_LED_MODE_NONE |
| if the fault affects the flash LED. Exactly which faults have such |
| an effect is chip dependent. Reading the faults resets the control |
| and returns the chip to a usable state if possible. |
| |
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| * - ``V4L2_FLASH_FAULT_OVER_VOLTAGE`` |
| - Flash controller voltage to the flash LED has exceeded the limit |
| specific to the flash controller. |
| * - ``V4L2_FLASH_FAULT_TIMEOUT`` |
| - The flash strobe was still on when the timeout set by the user --- |
| V4L2_CID_FLASH_TIMEOUT control --- has expired. Not all flash |
| controllers may set this in all such conditions. |
| * - ``V4L2_FLASH_FAULT_OVER_TEMPERATURE`` |
| - The flash controller has overheated. |
| * - ``V4L2_FLASH_FAULT_SHORT_CIRCUIT`` |
| - The short circuit protection of the flash controller has been |
| triggered. |
| * - ``V4L2_FLASH_FAULT_OVER_CURRENT`` |
| - Current in the LED power supply has exceeded the limit specific to |
| the flash controller. |
| * - ``V4L2_FLASH_FAULT_INDICATOR`` |
| - The flash controller has detected a short or open circuit |
| condition on the indicator LED. |
| * - ``V4L2_FLASH_FAULT_UNDER_VOLTAGE`` |
| - Flash controller voltage to the flash LED has been below the |
| minimum limit specific to the flash controller. |
| * - ``V4L2_FLASH_FAULT_INPUT_VOLTAGE`` |
| - The input voltage of the flash controller is below the limit under |
| which strobing the flash at full current will not be possible.The |
| condition persists until this flag is no longer set. |
| * - ``V4L2_FLASH_FAULT_LED_OVER_TEMPERATURE`` |
| - The temperature of the LED has exceeded its allowed upper limit. |
| |
| |
| |
| ``V4L2_CID_FLASH_CHARGE (boolean)`` |
| Enable or disable charging of the xenon flash capacitor. |
| |
| ``V4L2_CID_FLASH_READY (boolean)`` |
| Is the flash ready to strobe? Xenon flashes require their capacitors |
| charged before strobing. LED flashes often require a cooldown period |
| after strobe during which another strobe will not be possible. This |
| is a read-only control. |