Re: parport (i2c bus) maximum speed

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

On Fri, 13 Jun 2008 20:04:02 +0200, Petr Jakeš wrote:
> Maybe I was not specific enough. Actually there is an SCH3114 chip on our
> motherboard (http://www.smsc.com/main/catalog/sch311x.html ) and lm-sensors
> need dme1737 module for this chip.
> This chip acts as a SMBus master.

I seriously doubt it. I have the SCH311x datasheet under the eyes and
it doesn't even mention SMBus. Neither as a slave nor as a master.
Unless you are using GPIO pins to implement a bit-banged I2C bus using
a custom kernel driver...

The dme1737 driver supports the hardware monitoring block of the
SCH311x. This functionality is accessed over the LPC bus, not the SMBus.

> > I'm confused now. How is I2C/SMBus speed related to lm-sensors at all?
> 
> 
> I am confused as well :-)
> My feeling was lm-sensors are here to:
> 
>    1. enable SMBus/I2C communication (mainly using HW masters presented on
>    the motherboards)  to communicate with SMBus slaves (mainly presented on the
>    PC motherboards, ie clock, temperature, fans ....).
>    2. enable SMBus/I2C communication with some other chips which one can
>    connect to the bus

Today, lm-sensors is a library and a set of tools to let users monitor
their hardware, i.e. watch the temperatures, voltages and fans. These
monitoring devices can either be on the SMBus, or on the LPC bus. In
the former case, an additional driver is needed, but that's an
implementation detail. The I2C (SMBus) bus drivers are provided by the
kernel, and so are the hwmon drivers. I would be tempted to say that
the hwmon drivers no longer belong to "lm-sensors", but if you want to
think of them as belonging to lm-sensors, why not.

In the past, the lm-sensors package has included i2c bus drivers,
because they were not yet merged in the kernel and we needed them. But
that was years ago. Thinking of the i2c bus drivers as being part of
lm-sensors today is no good, because then you forget that many hardware
monitoring chips don't need I2C/SMBus at all, and that many I2C/SMBus
devices are not hardware monitoring chips.

The i2c mailing list and the i2c-tools SVN repository are hosted on
lm-sensors.org for historical reasons only. They are completely
independent from the lm-sensors project.

> Because of above mentioned we have done some development and we are able,
> using lm-sensors, to communicate with PIC microcontrolers (they are acting
> as I2C slaves) on the VIA and Unicorn motherboards. From our test it looks
> like we are communicating close to the 100kbps.

You are not using lm-sensors for that. You are using the kernel's i2c
bus drivers. lm-sensors is for hardware monitoring only.

-- 
Jean Delvare

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