[lkml]   [2003]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: PATCH : LEDs - possibly the most pointless kernel subsystem ever
> > Does anybody have any suggestions for recommended standard uses for
> > parallel port connected LEDs?

> At one point I had 12 LEDs on parport. LEDs were fast enough to be
> drive at interrupt entry/exit.
> They were:
> Yellow not idle task
> Green interrupt
> " bh
> " pagefault
> Red lowest 4 bits of PID
> Red, low intensity serial i/o
> " network i/o
> It actually looked very good. Glow of interrupt led told you
> interrupt load, pid LEDs told you about what kind of load it is
> experiencing (you could tell shell script from make and from
> computation, and if machine hard-died, you at least knew if it was
> interrupt or process context).

Sounds like exactly what we need. If we standardise on something like
the above, we could just have a CONFIG_FRONT_PANEL_MONITOR and ask
people to send in the LED status with bug reports.

> But this kind of blinkenlights needed pretty fast LEDs. (At 486 time
> I decided that parport on ISA is fast enough..)

I'll buy some LEDs and build a parallel port connected LED panel
tomorrow... Do you think the overhead of driving the LEDs would have
too much of a negative effect on system performance? If so, or if we
want more flexibility, maybe we could work out a design for a PCI
card, which could include more than 12 LEDs - 7-segment numeric
displays of pid, etc.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:47    [W:0.070 / U:4.136 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site