Re: i2c-tools - at24 vs eeprom - decode-dimms fails with the at24 module

[Jean Delvare <jdelvare@suse.de>]

Hi James,

On Sat, 14 Mar 2020 09:22:57 -0600, James Feeney wrote:
> The log says "kernel: eeprom 3-0050: eeprom driver is deprecated, please use at24 instead", but decode-dimms will only work with the deprecated eeprom driver.  With the at24 module, "Number of SDRAM DIMMs detected and decoded: 0".  With the eeprom module, "Number of SDRAM DIMMs detected and decoded: 6". This is on Arch Linux, with linux 5.5.9.arch1-2, on an old Asus P6T DELUXE V2 with a Core i7.

While the legacy eeprom driver (poorly) auto-detected SPD EEPROMs, the
at24 driver requires SPD EEPOMs to be explicitly enumerated. There is
work in progress [1] to automate this in some cases (namely x86 systems
using the i2c-i801 SMBus controller driver) but for now you'll have to
do it yourself from user-space. How to do that is explained in section 4
of:

https://www.kernel.org/doc/Documentation/i2c/instantiating-devices

TL;DR: Something like:

# echo spd 0x50 > /sys/bus/i2c/devices/i2c-3/new_device

should do the trick, if i2c-3 is your SMBus and you have 1 memory
module in the first slot. If you have more memory modules, use
"modprobe i2c-dev ; i2cdetect 0" to find out the proper addresses in
the 0x50-0x57 range and repeat the command.

I guess I should resubmit this patch set to make it transparent to the
users.

[1] https://lore.kernel.org/lkml/20191014113950.1f989ba6@endymion/

-- 
Jean Delvare
SUSE L3 Support