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

[Ingo Molnar <mingo@elte.hu>]

* Kay Sievers <kay.sievers@vrfy.org> wrote:

> > 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

i think that should be fixed by providing a compatible 
/proc/sys/dev/rtc/max-user-freq implementation in the new driver too.

> > 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"

but if it breaks max-user-freq (which is needed by qemu for example) 
then distros would likely disable it, right?

or this rule might be broken in some way. For example my Fedora 8 box 
has this in /etc/udev/rules.d/50-udev-default.rules:

 # miscellaneous
 KERNEL=="fuse",                 MODE="0666"
 KERNEL=="rtc|rtc0",             MODE="0644"
 KERNEL=="rtc0",                 SYMLINK+="rtc"

still i've got:

 crw------- 1 root root  10, 135 Dec 28 08:13 /dev/rtc
 crw-r--r-- 1 root root 254,   0 Dec 28 08:13 /dev/rtc0

_and_ my distro kernel doesnt even have CONFIG_RTC enabled - i run the 
Fedora 9 devel/rawhide kernel on this box:

 # CONFIG_RTC is not set
 # CONFIG_GEN_RTC is not set
 # CONFIG_HPET_RTC_IRQ is not set
 CONFIG_RTC_LIB=y
 CONFIG_RTC_CLASS=y
 # CONFIG_RTC_HCTOSYS is not set
 # CONFIG_RTC_DEBUG is not set
 # RTC interfaces
 CONFIG_RTC_INTF_SYSFS=y
 CONFIG_RTC_INTF_PROC=y
 CONFIG_RTC_INTF_DEV=y
 # CONFIG_RTC_INTF_DEV_UIE_EMUL is not set
 # CONFIG_RTC_DRV_TEST is not set

udev-116-3.fc8. Maybe i just misunderstood what the grand plan was here 
- i assumed it was to smoothly convert from old driver to new driver, 
without forcing any changes on user-space.

	Ingo