linux-kernel - Re: [rtc-linux] Re: [PATCH/RFC 0/5] Generic RTC class driver

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Message-ID: <alpine.LRH.2.00.0902251055260.4063@vixen.sonytel.be>
Date:	Wed, 25 Feb 2009 10:58:57 +0100 (CET)
From:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
To:	Brad Boyer <flar@...andria.com>
cc:	Alessandro Zummo <alessandro.zummo@...ertech.it>,
	Richard Zidlicky <rz@...ux-m68k.org>,
	rtc-linux@...glegroups.com, linux-parisc@...r.kernel.org,
	David@...abs.org,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Linux/PPC Development <linuxppc-dev@...abs.org>,
	Linux/m68k <linux-m68k@...ts.linux-m68k.org>,
	Woodhouse <dwmw2@...radead.org>
Subject: Re: [rtc-linux] Re: [PATCH/RFC 0/5] Generic RTC class driver

On Tue, 24 Feb 2009, Brad Boyer wrote:
> On Tue, Feb 24, 2009 at 07:37:08PM +0100, Alessandro Zummo wrote:
> > On Tue, 24 Feb 2009 18:56:03 +0100 (CET)
> > Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com> wrote:
> > > Converting all (ca. 20?) ppc and m68k RTC support code into individual RTC
> > > class drivers would add ca. 100+ lines of code for each individual driver.
> > 
> >  How different are all of those boards? It's simply a matter
> >  of parameters and offsets? can we group them somehow?
> 
> I imagine we could cut down the numbers somewhat with clever code sharing,
> but it's still going to be a fairly large number. I don't know all the
> embedded boards, but just with all the Macintosh models there are at
> least three and maybe four drastically different methods of RTC access,
> and all of them are directly tied to some chip that does something else
> completely unrelated. For one of them we don't even have a driver at the

Yeah, on Mac/m68k the RTC is usually handled by a chip that does lots of other
things, so you need to keep the bulk of the code in arch/m68k/ anyway.

> moment.  They also are all custom chips that wouldn't be used anywhere
> else. The other thing we need to keep in mind is that if we do it right
> we can share drivers across m68k and powerpc in some cases.  I imagine
> some of the embedded powerpc boards are using chips that are common in
> other architectures as well.

Many embedded powerpc boards already have RTC class drivers under drivers/rtc/,
as their RTC chips are sufficiently common.

The ones that don't are mostly "workstation" or "server" type hardware. The
full list is:
  - rtas_set_rtc_time
  - mpc8xx_set_rtc_time
  - beat_get_rtc_time
  - chrp_set_rtc_time
  - iSeries_set_rtc_time
  - maple_set_rtc_time
  - pmac_set_rtc_time
  - ps3_set_rtc_time

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
Fax:      +32 (0)2 700 8622
E-mail:   Geert.Uytterhoeven@...ycom.com
Internet: http://www.sony-europe.com/

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