Re: [PATCH 0/4] PM: Do not destroy/create devices while suspended (rev. 2)

Kay Sievers
2008-01-02T14:55:03Z

On Jan 2, 2008 2:15 PM, Ingo Molnar <mingo@elte.hu> wrote:
> A stupid question. The old RTC driver is in
> drivers/char/rtc.c, and maps to:
>
> crw-r--r-- 1 root root 10, 135 Oct 25 18:02 /dev/rtc
>
> the new driver is in drivers/rtc/*, and maps to:
>
> crw-r--r-- 1 root root 254, 0 Dec 12 02:30 /dev/rtc0
>
> but all the x86 distro boxes i have access to make use of /dev/rtc.
> There's no symlink set up from /dev/rtc to /dev/rtc0 either. So it
> appears to me that the new RTC driver isnt actually utilized on most
> distributions.
>
> shouldnt we provide a Kconfig way of replacing dev 10:135 with the new
> driver's 254:0 device? (while keeping all the current modes of operation
> as well, of course.) It's all supposed to be 100% ioctl ABI compatible
> with the old driver, right?

It's not compatible enough to "fake" only the old major/minor. Userspace
must be fixed not to depend on stuff like: /proc/sys/dev/rtc/max-user-freq:
http://lkml.org/lkml/2007/8/4/183

> That way distros could start migrating to it
> as well, without depending on any udev hackery.

It's in the default udev setup:
KERNEL=="rtc|rtc0", MODE="0644"
KERNEL=="rtc0", SYMLINK+="rtc"

Kay