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

[Guenter Roeck]

On 6/1/24 03:41, Thomas Weißschuh wrote:
> On 2024-05-31 22:42:24+0000, Guenter Roeck wrote:
> > On 5/31/24 16:05, Guenter Roeck wrote:
> > > Add support for reading SPD NVRAM data from SPD5118 (Jedec JESD300)
> > > compliant memory modules. NVRAM write operation is not supported.
> > >
> > > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > > ---
> > > v3: New patch
> > >
> > > RFT: I'd like to get some more test coverage before moving forward
> > >        with this patch. decode-dimms doesn't recognize the 'spd5118'
> > >        driver.
>
> Looks good to me.
>
> Spot-checking against JSED400-5B and the embedded CRC are as expected.
>
> > Looking for feedback:
> >
> > [ ... ]
> >
> > > +
> > > +	nvmem = devm_nvmem_register(dev, &nvmem_config);
> >
> > This returns ERR_PTR(-EOPNOTSUPP) if CONFIG_NVRAM=n. We have two options:
> >
> > - Ignore -EOPNOTSUPP and continue registering the hwmon device
> >
> > or
> >
> > - Add
> > 	select NVRAM
> > 	select NVRAM_SYSFS
> >    to the driver's Kconfig entry.
>
> s/NVRAM/NVMEM/g
>
> > Any preferences ?
>
> It seems reasonable to support the module without the eeprom logic.
> When used in a fixed, embedded environment, the eeprom is of limited
> value as it's known beforehand, while the hwmon functionality is still
> useful.

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 ?

Thanks,
Guenter