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diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst new file mode 100644 index 0000000000..d22c5efb80 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst @@ -0,0 +1,188 @@ +.. 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. + + +.. tabularcolumns:: |p{5.7cm}|p{11.8cm}| + +.. flat-table:: + :header-rows: 0 + :stub-columns: 0 + + * - ``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. + +.. tabularcolumns:: |p{7.5cm}|p{7.5cm}| + +.. flat-table:: + :header-rows: 0 + :stub-columns: 0 + + * - ``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. + +.. tabularcolumns:: |p{8.4cm}|p{9.1cm}| + +.. flat-table:: + :header-rows: 0 + :stub-columns: 0 + + * - ``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. |