Re: [PATCH i2c-tools] TODO: add file and describe items for the 4.5 release

["Brigham Campbell" <me@brighamcampbell.com>]

On Sun Jul 5, 2026 at 11:19 PM MDT, Stephen Horvath wrote:
> If you've got the spd5118 kernel module loaded (which usually happens
> automatically), you just have to run `sudo ./decode-dimms`. You can
> manually bind spd5118 if it isn't autodetecting, your dimms should be on
> your i801 bus (or PIIX4 for AMD), usually with an address between 0x50
> to 0x57.

No, the spd5118 module doesn't appear to be loaded automatically:

```
$ lsmod | grep spd5118
$ zgrep SENSORS_SPD5118 /proc/config.gz
CONFIG_SENSORS_SPD5118=m
CONFIG_SENSORS_SPD5118_DETECT=y
```

Using `i2cdetect` on the i801 SMBus controller, I see that it reports no
attached i2c devices:

```
$ sudo ./tools/i2cdetect -y /dev/i2c-15
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
$ 
```

Interestingly, I see warnings in dmesg upon running the above i2cdetect
command. Taking a quick look at the kernel code, this appears to be
caused by some transient controller hardware busy state which is
overcome by the kernel's bus arbitration retry logic (See
`drivers/i2c/busses/i2c-i801.c:1552`). It's strange that a bus with no
devices attached would ever become busy...

```
...
[  +0.000009] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[  +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[  +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[  +0.000009] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
[  +0.000010] i801_smbus 0000:00:1f.4: SMBus is busy, can't use it!
...
```

In any case, if I am unable to exercise your code, I would still be glad
to review it.

Cheers,
Brigham