Application to fade screen

Aapo Rantalainen aapo.rantalainen at
Sat Aug 16 18:56:23 CEST 2008

>I can't find out why open() has a third argument.
> I'm only used to seeing two and searching open for 3 arguments comes up with
> nothing.
Actually I do not why there are three arguments in open(), but it do
not work without the last 1.
I take that on this page:

>I don't get the purpose of writing numbers to the file?
This is not a normal file. This is the ancient UNIX (and therefor
modern Linux) way to handle with different kind of devices.

> Do the numbers control how much it fades?
Number is the wanted brightness.

> and what is 63 for?
63 is the maximum value.

I have never hearded about this file, until this messagechain, so I
ask the current value of it
cat /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/brightness
And it said 63. I wanted it more bright so I tried
echo 64 > /sys/devices/platform/s3c2440-i2c/i2c-adapter/i2c-0/0-0073/backlight/pcf50633-bl/brightness
And it said: echo: write error: Invalid argument
So I thought maybe 63 is the maximum value.

And surprisingly sametime in devel-list I got verification and much more:

If you are interested in other device-files, there are some list (not complete):

-Aapo Rantalainen

More information about the support mailing list