b/w reflective mode for monitor
dilinger at laptop.org
Thu Apr 5 03:30:05 EDT 2007
Mitch Bradley wrote:
> But there is a subterfuge that works. The LEDs happen to be driven by
> GPIO pins on the EC chip. From the main CPU, you can control the EC
> chip's GPIO pins. If you turn off the "output enable" bit on the pin
> that controls the power light, the light goes out. It seems unlikely
> that the EC firmware would notice that and turn it back on. Most code
> that deals with GPIOs sets up the basic configuration (enables, etc)
> once, then subsequently use the "output value" bits to control the pins.
> You can demonstrate this from the firmware as follows:
> ok d5 fc11 ec!
> That is a brute force way; in practice you would want to read the value,
> turn off the 02 bit, and write it back:
> ok fc11 ec@ 2 invert and fc11 ec!
> ec@ and ec! are shorthand Forth words that perform a little I/O port
> dance to access internal EC chip registers - write 0xfc to I/O port
> 0x381, write 0x11 to I/O port 0x382, then either read or write the value
> at I/O port 0x383.
That is all kinds of awesome. Should I add it to the kernel LED driver?
It would be neat to be able to control the wireless LEDs as well.
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