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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.

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I'd start my investigations with lspci, lsusb etc. Maybe you can see the device there. – January Oct 12 '12 at 7:47
To follow up on @January's comment, use qdbusviewer to check the device and simultaneously access its stats through D-Bus. This of course assumes you use Linux. – Deer Hunter Oct 12 '12 at 9:28


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

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


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).

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It outputs lot of data pastebin.com/TuqsfBG7 How can i use this? – gadelat Oct 13 '12 at 12:25
Not much interesting in there. I've edited my answer with more words to search (lux, lumin) and more things to try. – Stéphane Chazelas Oct 13 '12 at 13:13
What does lspci -Q output? – Deer Hunter Oct 14 '12 at 14:29

A few links:

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).

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