linux-kernel - Re: [RFC PATCH 09/13] mfd: rtc: support RTC on ROHM BD71828 with BD70528 driver

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Date:   Wed, 23 Oct 2019 10:27:43 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>
CC:     "dmurphy@...com" <dmurphy@...com>,
        "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "jacek.anaszewski@...il.com" <jacek.anaszewski@...il.com>,
        "a.zummo@...ertech.it" <a.zummo@...ertech.it>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "pavel@....cz" <pavel@....cz>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>
Subject: Re: [RFC PATCH 09/13] mfd: rtc: support RTC on ROHM BD71828 with
 BD70528 driver

Hello again Alexandre,

On Thu, 2019-10-17 at 12:48 +0200, Alexandre Belloni wrote:
> On 17/10/2019 10:36:44+0000, Vaittinen, Matti wrote:
> > Hello Alexandre,
> > 
> > Thanks for quick check! I'll be off for the rest of the week but I
> > will
> > re-work this patch at next week :) I agree with you regarding most
> > of
> > the comments.
> > 
> > > > +
> > > > +
> > > > +/*
> > > > + * RTC definitions shared between
> > > > + *
> > > > + * BD70528
> > > > + * and BD71828
> > > > + */
> > > > +
> > > > +#define ROHM_BD1_MASK_RTC_SEC		0x7f
> > > > +#define ROHM_BD1_MASK_RTC_MINUTE	0x7f
> > > > +#define ROHM_BD1_MASK_RTC_HOUR_24H	0x80
> > > > +#define ROHM_BD1_MASK_RTC_HOUR_PM	0x20
> > > > +#define ROHM_BD1_MASK_RTC_HOUR		0x3f
> > > > +#define ROHM_BD1_MASK_RTC_DAY		0x3f
> > > > +#define ROHM_BD1_MASK_RTC_WEEK		0x07
> > > > +#define ROHM_BD1_MASK_RTC_MONTH		0x1f
> > > > +#define ROHM_BD1_MASK_RTC_YEAR		0xff
> > > > +#define ROHM_BD1_MASK_ALM_EN		0x7
> > > > +
> > > 
> > > All that renaming is distracting and useless. Please resubmit
> > > without
> > > renaming defines, structs and functions to make it easier to
> > > review.
> > 
> > I would prefer renaming because it makes it clearly visible which
> > defines/structs/functions are common for both PMICs and which are
> > PMIC
> > specific. But I really understand the problem of spotting real
> > changes.
> > Would it be Ok if I did renaming in separate patch which does not
> > bring
> > in any other changes - and then the functional changes in separate
> > patch?
> > 
> 
> No, unless you can guarantee that all future PMICs from rohm matching
> the wildcard will use this driver.
> 
I started re-working this patch and remembered my original idea
regarding the naming :) I should have commented it as I had already
forgotten it. You are correct what comes to the difficulty of using
correct wild-cards. And I agree with you what comes to function and
struct names like bd7xx28 - those are somewhat fragile as next PMIC
which we want to support with this driver may be BD12345 - yielding our
wild-card useless.

But if we take a look of common definitions in header rohm-shared.h
which I added - those are prefixed as ROHM_BD1. My idea was introducing
this common RTC define group 1 - which would be common define group for
all devices which belong to BD1 group. Currently that would be BD71828
and BD70528. What was missing is the comment explaining this (and lack
of comment made this useless as even I forgot it already).

I already reverted this naming change and all BD70528 specific and
common defines/functions/enums are prefixed with the good old BD70528.
Only new definitions which I added for BD71828 are prefixed with
BD71828. But how do you see the grouping the common defines to format
ROHM_BD<group number>_FOO_BAR in the rohm-shared.h - with comment that
group BD1 consists of definitions which are common for BD70528 and
BD71828?

My only fear when using prefix BD70528 for common defines is that
someone changes some defines to match the BD70528 data-sheet without
evaluating if this impacts to other PMICs. It may be useless paranoia
though - hence I am asking for your opinion at this phase. I can do
this grouping in own patch - or just leave it as it is now in my local
repo - with the old BD70528 being common prefix.

Br,
	Matti Vaittinen