Re: [PATCH RFT v3 4/4] hwmon: (spd5118) Add support for reading SPD data

[Armin Wolf]

Am 01.06.24 um 16:08 schrieb Thomas Weißschuh:

> On 2024-06-01 06:48:29+0000, Guenter Roeck wrote:
>
> <snip>
>
> > Makes sense. Another question:
> >
> > This:
> >
> > +        struct nvmem_config nvmem_config = {
> > +               .type = NVMEM_TYPE_EEPROM,
> > +               .name = dev_name(dev),
> > +               .id = NVMEM_DEVID_AUTO,
> >
> > results in:
> >
> > $ ls /sys/bus/nvmem/devices
> > 0-00501  0-00512  0-00523  0-00534  cmos_nvram0
> > ^^^^^^^  ^^^^^^^  ^^^^^^^  ^^^^^^^
> >
> > which really doesn't look good. My current plan is to go with NVMEM_DEVID_NONE,
> > which results in
> >
> > $ ls /sys/bus/nvmem/devices
> > 0-0050	0-0051	0-0052	0-0053	cmos_nvram0
> >
> > We could also used fixed strings, but "spd" results in "spd[1-4]" which
> > I think would be a bit misleading since the DDR3/4 SPD data format is
> > different, and "spd5118" would result in "spd5118[1-4]" which again would
> > look odd. Any suggestions ?
> In order of descending, personal preference:
>
> * spd-ddr5-[0-3] (.id = client->address - 0x50)

Hi,

this will break as soon as more than 8 DDR5 DIMMs are installed.

> * spd-ddr5-[0-3] (NVMEM_DEVID_AUTO)
> * Same with only "ddr5-"
> * spd5118-[0-3]
> * Your proposal from above
> * nvmem[0-3] (default handling)
> * 0-0050-[0-3]
>
> Also can't a user of the eeprom already figure out which kind of module
> it is by looking at the eeprom contents?
> The first few bytes used for that seem to be compatible between at least
> DDR4 and DDR5.
>
> So using plain spd[1-4] could be enough.

This could cause problems when DDR6 arrives.
Personally i would prefer the spd5118-X (NVMEM_DEVID_AUTO) format.

Thanks,
Armin Wolf