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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 29 Oct 2019 14:50:21 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.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

On 23/10/2019 10:27:43+0000, Vaittinen, Matti wrote:
> 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.
> 

I don't think those masks will ever change, all the BCD RTCs are using
the same.

Note that ROHM_BD1_MASK_RTC_HOUR_24H, ROHM_BD1_MASK_RTC_HOUR_PM and
ROHM_BD1_MASK_ALM_EN are bits and should use BIT() to make that clear.
Those may change later but I don't see how someone looking at the
BD70528 datasheet would get those wrong.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com