Some of this afternoon I've been hacking away writing a *very* simple console driver that pulses the keyboard LED using asynchronous pulses identical to that of RS232 serial. The idea is to hook up a photo diode and convert the light signal into asynchronous pulses into a USB serial dongle that's connected to a debugging host PC. Then I should be able to do printk() over the keyboard LED and be able do debug the kernel when I don't have the luxury of a video console. :-)
OK, so the speed may be very slow, ~300 baud, but it may just work. If it does, it will get me out of all sorts of painful debugging holes where I don't have the luxury of being able to debug using POST codes by writing to port 0x80.
I will let you know if it works once we get some kit to read the LED reliably and at speed...
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