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

[Ingo Molnar <mingo@elte.hu>]

(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