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

[Geert Uytterhoeven]

On Fri, 27 Feb 2009, Richard Zidlicky wrote:
> On Wed, Feb 25, 2009 at 11:18:36AM +0100, Alessandro Zummo wrote:
> > On Wed, 25 Feb 2009 11:00:13 +0100 (CET)
> > Geert Uytterhoeven <Geert.Uytterhoeven at sonycom.com> wrote:
> > 
> > > I didn't know NTP was broken with RTC class drivers?
> > > 
> > > So we should actually keep on using genrtc instead of rtc-ppc/rtc-generic for
> > > now? ;-)
> > 
> >  broken here means that the kernel won't save the time to the hardware
> >  rtc every 11 minutes as it used to do. normal NTP operations are unaffected.
> 
> seems like so far ppc is the only architecture attempting to implement it
> correctly, all others either have it unimplemented or use the broken
> by design set_rtc_mmss method. 
> Also note that in most cases hwclock has much better possibilities
> to do a good job.
> 
> Regarding genrtc vs rtc-ppc/rtc-generic it is worth noting that genrtc
> provides RTC_UIE emulation which is of some use for exotic programs like 
> "chrony".
> Afaics this is also the only situation without a good userspace workaround 
> and chrony never worked well for me so I have nothing against junking the 
> code.

What about CONFIG_RTC_INTF_DEV_UIE_EMUL for RTC class devices?

> Regarding a possible reorganisation from the generic to all separate drivers
> I agree that the habit of putting rtc-chip specific code in asm-generic is 
> confusing at best. 
> In many cases such code might be better placed in drivers/rtc or 
> include/linux/rtc/chipname.
> 
> Imho this does not preclude the possibility to use a generic framework. While
> there certainly are valid reasons to have separate drivers in some cases 
> I do not see much value in rewriting everything as separate drivers where 
> the generic framework works well.

Indeed. You can have a working RTC class driver for lots of hardware by just
writing ca. 100 lines of code on top of the generic framework.

With kind regards,

Geert Uytterhoeven
Software Architect

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