Re: Porting OpenBSD's sysctl hw.sensors framework to FreeBSD

In message <20070711144240.a3gdtxjvqcwkg4o4@xxxxxxxxxxxxxxxxxxxxx>, Alexander Leidinger writes:

I was not thinking about 7-layer-OSI, I was thinking about 3 layers:
presentation, infrastructure and "low-level" data acquiring stuff (I
prefer the pragmatic way of looking at things).

This again misses the point, because you assume a simple bottom-up
architecture will work like it does for PCI devices.

In this case however, the majority of systems need some piece of code
to identify them, look up in a table (which we get from where ?) and
configure the sensors.

Sensor hardware is not context-free and selfidentifying like PCI and
USB devices, in fact, it is about as far from PnP as you can get.

Finding an LM75 and reading the temperature is worth next to nothing
if you don't know where the LM75 is mounted.

Reading an ADC is worth absolutely nothing, if you don't know what
it measures and what voltage dividers are in front of it.

Finding an I2C sensor and trying to read it is a catastrophe when
it turns out not to be a sensor but the motherboard clock generator
or voltage regulater.

IFF we want to do something more comprehensive than the gaggle of
ports, then we want to do it properly so that it doesn't weigh down
the kernel with tons of, on average unused, junk, doesn't imperil
hardware and delivers sensor readings which come with the necessary
context to have a real physical meaning.

Access to I2C busses and I/O registers should happen in the kernel,
but maintaining a database of all sorts of weird systems should not.

--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@xxxxxxxxxxx | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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