N900 Hardware Flash Torch
Hardware
The flash torch on the N900 is a ADP1653 two LED flash, which has several modes. It can flash brightly for a maximum of 0.5 s, with an LED current of no more than 320 mA, or be in torch mode, at a current of no more than 50 mA.
Exceeding these values will cause hardware damage.
The brightness of the LED in flashlight mode is approximately 20 lux at 1 m at the brightest spot in the beam.
It also contains a red indicator light, to indicate video is being recorded.
Software
(See kernel source ./arch/arm/mach-omap2/board-rx51-camera.c for details)
The controls of the device are apparently presented as video4linux ioctls related to the main camera device - /dev/video0 usually, and should show up in a suitable 'webcam' type viewer that can show arbitrary video4linux controls.
The driver is in drivers/media/video/adp1653.c
This is used by the built-in camera application, and a third party flashlight application, as well as being controllable by a live focus application which can also control the LEDs.