Documentation: leds: Add description of v4l2-flash sub-device
This patch extends LED Flash class documention by the description of interactions with v4l2-flash sub-device. Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com> Acked-by: Kyungmin Park <kyungmin.park@samsung.com> Cc: Richard Purdie <rpurdie@rpsys.net> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Bryan Wu <cooloney@gmail.com>
This commit is contained in:
parent
589fca16c1
commit
aaf2cbca46
|
@ -20,3 +20,54 @@ Following sysfs attributes are exposed for controlling flash LED devices:
|
|||
- max_flash_timeout
|
||||
- flash_strobe
|
||||
- flash_fault
|
||||
|
||||
|
||||
V4L2 flash wrapper for flash LEDs
|
||||
=================================
|
||||
|
||||
A LED subsystem driver can be controlled also from the level of VideoForLinux2
|
||||
subsystem. In order to enable this CONFIG_V4L2_FLASH_LED_CLASS symbol has to
|
||||
be defined in the kernel config.
|
||||
|
||||
The driver must call the v4l2_flash_init function to get registered in the
|
||||
V4L2 subsystem. The function takes six arguments:
|
||||
- dev : flash device, e.g. an I2C device
|
||||
- of_node : of_node of the LED, may be NULL if the same as device's
|
||||
- fled_cdev : LED flash class device to wrap
|
||||
- iled_cdev : LED flash class device representing indicator LED associated with
|
||||
fled_cdev, may be NULL
|
||||
- ops : V4L2 specific ops
|
||||
* external_strobe_set - defines the source of the flash LED strobe -
|
||||
V4L2_CID_FLASH_STROBE control or external source, typically
|
||||
a sensor, which makes it possible to synchronise the flash
|
||||
strobe start with exposure start,
|
||||
* intensity_to_led_brightness and led_brightness_to_intensity - perform
|
||||
enum led_brightness <-> V4L2 intensity conversion in a device
|
||||
specific manner - they can be used for devices with non-linear
|
||||
LED current scale.
|
||||
- config : configuration for V4L2 Flash sub-device
|
||||
* dev_name - the name of the media entity, unique in the system,
|
||||
* flash_faults - bitmask of flash faults that the LED flash class
|
||||
device can report; corresponding LED_FAULT* bit definitions are
|
||||
available in <linux/led-class-flash.h>,
|
||||
* torch_intensity - constraints for the LED in TORCH mode
|
||||
in microamperes,
|
||||
* indicator_intensity - constraints for the indicator LED
|
||||
in microamperes,
|
||||
* has_external_strobe - determines whether the flash strobe source
|
||||
can be switched to external,
|
||||
|
||||
On remove the v4l2_flash_release function has to be called, which takes one
|
||||
argument - struct v4l2_flash pointer returned previously by v4l2_flash_init.
|
||||
This function can be safely called with NULL or error pointer argument.
|
||||
|
||||
Please refer to drivers/leds/leds-max77693.c for an exemplary usage of the
|
||||
v4l2 flash wrapper.
|
||||
|
||||
Once the V4L2 sub-device is registered by the driver which created the Media
|
||||
controller device, the sub-device node acts just as a node of a native V4L2
|
||||
flash API device would. The calls are simply routed to the LED flash API.
|
||||
|
||||
Opening the V4L2 flash sub-device makes the LED subsystem sysfs interface
|
||||
unavailable. The interface is re-enabled after the V4L2 flash sub-device
|
||||
is closed.
|
||||
|
|
Loading…
Reference in New Issue