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

On Jan 2, 2008 2:15 PM, Ingo Molnar [off-list ref] 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