[lm-sensors] sysfs interface for fan present capability

[Henrique de Moraes Holschuh]

On Sun, 04 Jun 2006, Hans de Goede wrote:
> I think they are just seeing if it gives any "ticks" at all, so it won't
> detect a 2 wire fan even if connected to one if its headers.

Two-wire fans can be detected just as well as three-wire ones, if you
measure current draw :)  In fact, some chips (like the lm75) can actually
COUNT ticks on two-wire fans by measuring spikes in the current draw...

If you detect fan presence using ticks, you will never detect a stuck fan on
startup, which is *dangerous* as it could cause the software inhibit an
alarm on that fan.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh