linux-kernel - Re: [PATCH v2 1/6] rtc: m68k: provide rtc_class

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Message-ID: <4888267.R0sXv0tuDQ@wuerfel>
Date:	Wed, 27 Apr 2016 12:34:19 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Helge Deller <deller@....de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Rich Felker <dalias@...c.org>,
	David Howells <dhowells@...hat.com>,
	alpha <linux-alpha@...r.kernel.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Parisc List <linux-parisc@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	linux-m68k <linux-m68k@...ts.linux-m68k.org>,
	RTCLINUX <rtc-linux@...glegroups.com>,
	Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v2 1/6] rtc: m68k: provide rtc_class_ops directly

On Wednesday 27 April 2016 09:47:56 Geert Uytterhoeven wrote:
> > --- a/arch/m68k/kernel/time.c
> > +++ b/arch/m68k/kernel/time.c
> > @@ -86,7 +86,24 @@ void read_persistent_clock(struct timespec *ts)
> >         }
> >  }
> >
> > -#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
> > +#if defined(CONFIG_ARCH_USES_GETTIMEOFFSET) && defined(CONFIG_RTC_DRV_GENERIC)
> 
> s/defined/IS_ENABLED/ for the modular case.

Thanks, fixed in all three architectures/

> > @@ -95,7 +112,10 @@ static int __init rtc_init(void)
> >         if (!mach_hwclk)
> >                 return -ENODEV;
> >
> > -       pdev = platform_device_register_simple("rtc-generic", -1, NULL, 0);
> > +       /* or just call devm_rtc_device_register instead? */
> 
> I guess this comment is a bogus leftover? There's no "dev" parameter to
> pass to devm_rtc_device_register() here.

Sort of. When I wrote it, I thought that a NULL argument would work,
and I later found out myself that it doesn't.

I'll drop the comment there, but there are still a few ways we (probably
not me, but whoever is interested) could take this further:

- register both the device and the driver here, and call
  devm_rtc_device_register from the probe function so we can move away
  from drivers/rtc/rtc-generic.c

- do this separately for mac, mvme147, mvme16x, sun3, q40 and sun3x

- move the six implementations into drivers/rtc as standalone drivers.

One (AFAIK) unsolved problem here is the question of how to handle
read_boot_clock/read_persistent_clock/update_persistent_clock in this
case. This is a really odd API that is implemented in various ways
on a few major architectures, and not at all on others, so it's all
highly inconsistent.

	Arnd