On Mon, Nov 12, 2001 at 10:56:44AM -0800, Jun Sun wrote: > Jun Sun wrote: > > > > Pete Popov wrote: > > > > > > On Mon, 2001-11-12 at 05:29, Maciej W. Rozycki wrote: > > > > On Mon, 12 Nov 2001, Geert Uytterhoeven wrote: > > > > > > > > > > Unless you use a non-MC146818 RTC, which you need to write a separate > > > > > > driver for anyway. > > > > > > > > > > Yep, so that's why both m68k and PPC have common routines to read/write the > > > > > RTC, with a /dev/rtc-compatible abstraction on top of it. > > > > > > > > OK, then you need an RTC chipset-specific driver and not a CPU > > > > architecture-specific one. Otherwise we'll end with a zillion of similar > > > > RTC drivers like we already have for LANCE and SCC chips. > > > > > > I agree. We don't have arch specific network drivers so why have arch > > > specific rtc drivers. > > > > > > > Because we can have a free RTC driver working once you get kernel working. > > > > Actually there is a longer answer with a little bit of the background info. > > Kernel needs to know about the real calendar time when it boots up. And > optionally it may write to RTC (based on the assumption that kernel timer is > more accurate than RTC clock). So it already has abstraction, one form or > another, to do RTC read/write. > > Based on these abstractons you can provide a hardware-independent RTC driver, > with RTC read/write operations. Right. > Before CONFIG_NEW_TIME_C is introduced, each MIPS board has its own time > service routine, which means, even if RTC driver wants to utilize the > abstraction, it will be only for that board only. > > After CONFIG_NEW_TIME_C is introduced, that RTC abstract becomes MIPS-common. > Therefore, we can afford a MIPS-common generic RTC driver. No. This sounds _exactly_ like the PPC driver. What we need to do, and what I intend to do in 2.5 is make this a bit more generic so thatr any arch can fill out some infos and say we read like this, we write like that and that's that. > If that abstraction ever becomes Linux-common code, then the generic RTC > driver will essentially be a Linux-common, device-indpendent driver. Yeap. I wanna do this in 2.5. > For most MIPS machine, we need /dev/rtc to merely set time and read time. The > generic driver should suffice. Otherwire, you can wirte a complete one for a > specific board or a specific chip. The 'rtc' driver in drivers/char does read, write, some ioctls and a /proc bit. We can make this a bit more 'generic' -- Tom Rini (TR1265) http://gate.crashing.org/~trini/
