linux-kernel - Re: [PATCH V1 04/10] watchdog: da9061: watchdog driver (RFC)

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Date:   Thu, 6 Oct 2016 11:49:27 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Steve Twiss <stwiss.opensource@...semi.com>
Cc:     Wim Van Sebroeck <wim@...ana.be>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Zhang Rui <rui.zhang@...el.com>,
        DEVICETREE <devicetree@...r.kernel.org>,
        LINUX-INPUT <linux-input@...r.kernel.org>,
        LINUX-PM <linux-pm@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Support Opensource <Support.Opensource@...semi.com>,
        LINUX-KERNEL <linux-kernel@...r.kernel.org>,
        LINUX-WATCHDOG <linux-watchdog@...r.kernel.org>
Subject: Re: [PATCH V1 04/10] watchdog: da9061: watchdog driver (RFC)

Hi Steve,

On Thu, Oct 06, 2016 at 04:28:14PM +0000, Steve Twiss wrote:
> Hi Guenter,
> 
> Thanks for your reply.
> 
> On 06 October 2016 14:28, Guenter Roeck, wrote:
> 
> > To: Steve Twiss; LINUX-KERNEL; LINUX-WATCHDOG; Wim Van Sebroeck
> > Subject: Re: [PATCH V1 04/10] watchdog: da9061: watchdog driver
> 
> [...]
> 
> > > @@ -180,6 +180,11 @@ static const struct watchdog_info da9062_watchdog_info = {
> > >  	.identity = "DA9062 WDT",
> > >  };
> > >
> > > +static const struct watchdog_info da9061_watchdog_info = {
> > > +	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
> > > +	.identity = "DA9061 WDT",
> > 
> > This adds a lot of complexity to the driver just to be able to display "DA9061".
> > Why not just change the existing identity to "DA9061/DA9062 WDT" ?
> 
> This is true.
> I am using the compatible string to pick a different configuration .data block:
> 
> { .compatible = "dlg,da9062-watchdog", .data = &da9062_watchdog_info },
> { .compatible = "dlg,da9061-watchdog", .data = &da9061_watchdog_info },
> 
> when the only real difference between the DA9061 and DA9062 watchdog driver
> is the name. Functionally they are identical in this case.
> This was a similar comment in Dialog's internal review on this exact same point.
> "Why not just report one thing?"
> 
> My answer to that was because it would allow to distinguish between different chips.
> The watchdog driver would report the correct chip type, despite the driver always
> being for DA9062.
> 
> This exact same thing would happen with da9063-onkey and da9062-thermal also.
> For the ONKEY it is marginally confused by needing to support 63, but for 62 and 61
> it is the same thing. Only the name is different.
> 
> I have TO:'d Dmitry Torokhov; Eduardo Valentin; Zhang Rui, for that reason.
> 
> But, it is just my opinion to keep the "name" different.
> This will not be my decision if accepted into the Linux kernel, but I would like to 
> at least be consistent for DA9061 and DA9062 so ... is this an issue?
> 

Yes, for me it is. The driver is still the same, and I don't see the point
of increasing code size and making the driver less readable just to be able
to report a slightly different driver identification string. And each time
a similar HW is added we would go through the same effort, again for no good
reason.

FWIW the driver doesn't really need to be updated in the first place.
A compatible statement listing both da9061 and da9062 would do it. Plus,
on top of that, even your change would not guarantee that the output is correct.
A DT entry with lists da9061 compatibility on a da9062 system would report the
"wrong" name. And still work. So I really don't see the point.

Guenter