Intel ICH7 SMBus support, ichsmb(4)

Jeremy Chadwick koitsu at
Thu Sep 11 04:33:29 UTC 2008

On Wed, Sep 10, 2008 at 11:19:10PM +0100, Bruce M Simpson wrote:
> Hi there,
> I have been looking at a system which has the Intel ICH7 south bridge.
> Whenever I try to probe the SMBus on this system with 'smbmsg -p', I get  
> a lot of status=41 timeout messages in dmesg from the ichsmb(4) driver.
> I have been given the addresses of the SMBus peripherals and have tried  
> initiating reads to their register space directly using 'smbmsg', with  
> the same result.

Yes, I have seen this behaviour but *only* when querying a slave address
which was incorrect or had no device tied to it.  You should not be
using the "8-bit data address".

> * Has anyone seen the same issues with the ICH7?

All of my development on bsdhwmon has been done exclusively on ICH7
chipsets, except for the hardware I don't have access to (which use
other chipsets, but still use ichsmb(4)):

During early development of bsdhwmon, I used smbmsg exclusively for

So in that respect, no, I've never seen the problem you report.

> * Does anyone know of any userland code I could use as an alternative to 
> the ichsmb(4) driver?
> I looked at mbmon, it appears it relies on the smb(4) drivers; its  
> direct ISA access only works for specific hardware monitoring chips  
> which appear on the ISA/LPC bus and does not implement SMBus bit-banging  
> in userland.

mbmon does not use SMBus properly, or in the way you think it would.
It's a bad example.

If you would like some real code that interfaces with ichsmb(4)
reliably, let me know and I'll send you the current tarball to bsdhwmon.
It's very clean/easy to follow code.

If you're working on a hardware monitoring tool, possibly it would just
be best for me to include support for it in bsdhwmon.

| Jeremy Chadwick                                jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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