Re: [PATCH v5 2/4] hwmon: max31827: Add support for max31828 and max31829

[Guenter Roeck]

On 10/27/23 08:05, Matyas, Daniel wrote:
> > -----Original Message-----
> > From: Guenter Roeck <groeck7@xxxxxxxxx> On Behalf Of Guenter Roeck
> > Sent: Friday, October 27, 2023 5:52 PM
> > To: Matyas, Daniel <Daniel.Matyas@xxxxxxxxxx>
> > Cc: Jean Delvare <jdelvare@xxxxxxxx>; Jonathan Corbet
> > <corbet@xxxxxxx>; linux-hwmon@xxxxxxxxxxxxxxx; linux-
> > doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v5 2/4] hwmon: max31827: Add support for
> > max31828 and max31829
> >
> > [External]
> >
> > On 10/27/23 06:00, Matyas, Daniel wrote:
> > [ ... ]
> >
> > > > I also don't understand why that would be chip specific. I don't see
> > > > anything along that line in the datasheet.
> > > >
> > > > Ah, wait ... I guess that is supposed to reflect the chip default.
> > > > I don't see why the chip default makes a difference - a well defined
> > > > default must be set either way. Again, there is no guarantee that the
> > > > chip is in its default state when the driver is loaded.
> > >
> > > The well defined default was set in v4, but I deleted it, because the
> > default value in hex for max31827 and max31828 alarm polarity, and
> > max31827 fault queue is 0x0. I had 2 #defines for these values, but you
> > said:
> > > " Since MAX31827_ALRM_POL_LOW is 0, this code doesn't really do
> > anything and just pollutes the code."
> > > So, I thought I should remove it altogether, since res is set to 0 in the
> > beginning and the default value of these chips (i.e. 0) is implicitly set.
> > > > Also, why are the default values added in this patch and not in the
> > > > previous patch ?
> > >
> > > In v4 these default values were set in the previous patch.
> >
> > I asked you (or meant to ask you) to stop overwriting 0 with 0 in a
> > variable. I didn't mean to ask you (if I did) to stop writing the default value
> > into the chip. Sorry if I did; if so, that was a misunderstanding.
> >
> > Guenter
>
> Well, writing the default value into res, would just overwrite 0 with 0. Should I still do it?

No, that is not correct. You don't know what is in the chip register.
It may not be the chip default.

Guenter