On Tue, Nov 22, 2011 at 12:28 PM, Kay Sievers <kay.siev...@vrfy.org> wrote: >> #1 -- check for the hctosys property. If _any_ rtc present in the >> system has sysfs attribute hctosys == 1, it means that the kernel took >> care of it all, and userland doesn't need to call hwclock, at all. > > Systemd requires that the time was set by the kernel. It does not > support any other config natively, that would be done by plugging-in > hwclock like it was on non-systemd systems.
Cool. That's very appropriate given a minimally modern linux kernel... > The kernel's hctosys is hard coded in the kernel config, right? It is set by the kernel to 1, only when CONFIG_RTC_HCTOSYS_DEVICE is set, and when the device is the device named in this config var. If you don't have CONFIG_RTC_HCTOSYS_DEVICE, then the kernel won't sync system time during boot, and your rtc device will have hctosys==0. So if systemd counts on the kernel to set system time during boot, then you already depend on CONFIG_RTC_HCTOSYS_DEVICE, and you should be all set :-) >> #2 -- is customary to prefer /dev/rtc if present -- so that we can >> symlink to the right rtc from udev. src/util.c seems to hardcode rtc0. > > Udev does that by default today: > SUBSYSTEM=="rtc", DRIVERS=="rtc_cmos", SYMLINK+="rtc" Yes, but that means that it expects other programs to first try to open /dev/rtc . So to complete the picture, I think src/util.c should try /dev/rtc first :-) > If possible, we could invent a /dev/rtc-systemtime symlink and use > that, if its not needed during bootup before udev is started and has > created the symlink? that be the same as /dev/rtc I think... so no need for it that I can see. m -- martin.langh...@gmail.com mar...@laptop.org -- Software Architect - OLPC - ask interesting questions - don't get distracted with shiny stuff - working code first - http://wiki.laptop.org/go/User:Martinlanghoff _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel