linux-kernel - Re: [PATCH v4 1/2] iio: pressure: dps310: Refactor startup procedure

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Date:   Sun, 11 Sep 2022 10:56:25 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Eddie James <eajames@...ux.ibm.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-iio <linux-iio@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Joel Stanley <joel@....id.au>
Subject: Re: [PATCH v4 1/2] iio: pressure: dps310: Refactor startup
 procedure

On Tue, 6 Sep 2022 14:48:20 -0500
Eddie James <eajames@...ux.ibm.com> wrote:

> On 8/20/22 06:49, Jonathan Cameron wrote:
> > On Fri, 19 Aug 2022 12:42:00 +0300
> > Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> >  
> >> On Mon, Aug 15, 2022 at 4:42 PM Eddie James <eajames@...ux.ibm.com> wrote:  
> >>> On 8/12/22 17:03, Andy Shevchenko wrote:  
> >>>> On Wed, Aug 10, 2022 at 12:12 AM Eddie James <eajames@...ux.ibm.com> wrote:  
> >> ...
> >>  
> >>>>> +       rc = regmap_write(data->regmap, 0x0e, 0xA5);
> >>>>> +       if (rc)
> >>>>> +               return rc;
> >>>>> +
> >>>>> +       rc = regmap_write(data->regmap, 0x0f, 0x96);
> >>>>> +       if (rc)
> >>>>> +               return rc;  
> >>>> This code already exists, but still want to ask, is it really
> >>>> byte-registers here and not be16/le16 one? In such a case perhaps bulk
> >>>> write can be used to reflect it better?  
> >>> The temperature and pressure regs are 24 bits big endian, and all the
> >>> rest are 8 bits. I think the existing approach is best.  
> >> It doesn't look like you got what I was meaning... Or I misunderstood
> >> what you said.
> >>
> >> The code above writes two byte values to two sequential registers
> >> which make me think that they are 16-bit registers at offset 0x0e.  
> > Given they are undocumented, this is guessing territory.
> > Probably best to just leave them as is.
> > You could do a bulk write on an array though as that implies
> > nothing about what's in the registers -just that they happen
> > to be next to each other.  
> 
> 
> Indeed. Is it worth it to switch to bulk write for two 2-byte writes? 
> I'm inclined to say no and will leave this as-is for v6, but if you 
> think it is, I can switch it.
> 

As far as I'm concerned, fine either way.

Jonathan

> 
> Thanks,
> 
> Eddie
> 
> 
> >  
> >> ...
> >>  
> >>>>> +       rc = regmap_write(data->regmap, 0x0e, 0x00);
> >>>>> +       if (rc)
> >>>>> +               return rc;
> >>>>> +
> >>>>> +       return regmap_write(data->regmap, 0x0f, 0x00);  
> >> Ditto.
> >>