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Hello,

On Jul 30, 2007, at 00:19, Steven M. Bellovin wrote:

> On Mon, 30 Jul 2007 00:08:59 -0400
> Michael Lorenz <macallan@netbsd.org> wrote:
>
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>> Hello,
>>
>> On Jul 29, 2007, at 23:34, Daniel Carosone wrote:
>>
>>> On Mon, Jul 30, 2007 at 05:29:13AM +0200, Quentin Garnier wrote:
>>>> SMBus is a lot like I2C, and you will usually find various kind of
>>>> sensors attached there.
>>>
>>> How?
>>
>> You can probe for most of them - just issue a read and see if
>> something answers. SMBus is just another protocol layer on top of iic.
>>
>>> Specifically, once I have an iic at smbus, how do I find what
>>> sensors are attached there?  There are a few examples in GENERIC,
>>> with specific addresses for specific motherboards.
>>
>> Most iic devices have hardcoded addresses but since the address space
>> is pretty limited those addresses aren't unique but if you know the
>> address you can at least narrow the list of candidates down a lot.
>>
>> So, with iic you can's do much more than guess what's there, you're
>> expected to know. SMBus devices can be discovered and identified
>> though.
>
> This is all great (and I'm building new systems right now for my laptop
> and my desktop), but I still don't know what I'm likely to find.
> Temperature?  Fan speed?  Computation speed in furlongs/fortnight?

Probably all of that. Or nothing. You almost certainly have some sort 
of sensor/fan controller chip but there's no way for me to tell what it 
is, if it's an smbus or a plain iic device, if it's something we have a 
driver for etc.

If PCs had sane firmware we'd just have to look at the device tree...

have fun
Michael
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