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

On Wednesday, 2 of January 2008, Ingo Molnar wrote:

(David Brownell Cc:-ed too)

* Rafael J. Wysocki [off-list ref] wrote:

quoted

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.

I think so.

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.

Question for Dave. ;-)

quoted

quoted

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)

Well, if the graphics is sufficiently broken, it won't resume at all.

The "echo core > /sys/power/pm_test && echo mem > /sys/power/state" thing
should always work, though (IOW, if this doesn't work, we cartainly have a
bug).

Rafael