How to measure light?

Question

I've got a Dell Latitude E6410 notebook which changes lcd light intensity in response to ambient light levels, so it has to have some photocell. How can I access the data from this photocell? I tried different google searches like lux meter, light intensity monitor and so on and did not find a single right thing.

Answer 1

Try:

find /proc /sys | grep -ie brightness -e light -e lux -e lumin

On this laptop (a MacBookPro), it reveals (among other things):

/sys/devices/platform/applesmc.768/light

which is neither over PCI or USB.

You could try the same after

sudo modprobe -a tsl2550 isl29003 isl29020 apds9802als apds990x bh1770glc bh1780gli

which are drivers for various ambient light sensors.

You could also try sensors-detect or i2cdetect and see what they find. Possibly some information is made available from the BIOS (see dmidecode, acpidump, acpiextract, iasl).

Answer 2

A few links:

• http://www.kernel.org/doc/menuconfig/drivers-misc-Kconfig.html (to access data from the sensor the kernel must know about the device!)
• http://forum.notebookreview.com/dell-latitude-vostro-precision/475324-e6410-owners-thread-91.html

I do not know what the ALS is in your particular case, but as @January said, you may start from the lspci -Q utility output (which requires an Internet connection to query/requery all IDs - use -q for unknown IDs only).