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

Ingo Molnar
2008-01-02T13:16:57Z

(David Brownell Cc:-ed too)

* Rafael J. Wysocki <rjw@sisk.pl> wrote:

> Well, we have the following test script in the userland suspend
> package that is supposed to work right now:
>
> #!/bin/bash
> date
> cd /sys/class/rtc/rtc0
> echo $(( $(cat since_epoch) + 20 )) > wakealarm
> s2ram
> date
>
> provided that the new rtc driver code is compiled (and the old one is not).

ok, will try that. 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? That way distros could start migrating to it
as well, without depending on any udev hackery.

> > That way any suspend breakage would be detectable (and bisectable)
> > in automated testing - if the resume does not come back after 10-20
> > seconds then the test failed.
>
> Yes, but please note that some systems require user space
> manipulations of the graphics adapter for suspend to work and to
> detect a breakage of such a system you need to boot it into X and use
> s2ram to suspend.

yeah, i wouldnt expect graphics mode to come back without quirks. But it
should still work fine over the network, right? (which is my main mode
of testing anyway)

Ingo