Arch Linux

infoball

Member

From: Sweden

Registered: 2008-01-28

Posts: 6

No wakelarm due to kernel configured with old "Enhanced RTC" options

Hi,

I am an Arch newbie building a mythtv box for the first time and it's going really well! Arch really let's me do what I want to do and doesn't hide stuff, thus letting me solve any problems quite easily. However, I have just encountered a bit of a snag so I need some advice.

I want to have the machine start up in time for scheduled recordings, and so I need to use the RTC wakeup function of the motherboard. The Mythtv wiki suggests using the new /sys/class/rtc/rtc0/wakealarm interface, but Arch (kernel 2.6.23.14, x86_64) seems to be configured in a way that makes it impossible, here's the relevant text from the Mythtv wiki (http://www.mythtv.org/wiki/index.php/ACPI_Wakeup):

Warning: The wakealarm interface is incompatible with the kernel's old "Enhanced Real Time Clock Support" and "Generic /dev/rtc emulation" options. If your kernel was built with these enabled your kernel log will contain messages such as

rtc_cmos: probe of 00:03 failed with error -16

The solution is to rebuild your kernel with the above two options excluded (find them under Drivers -> Character Devices) and the various RTC interfaces (found under Drivers -> Real Time Clock) included. From a .config point of view CONFIG_RTC and CONFIG_GEN_RTC must be unset and, at a minimum, RTC_INTF_SYSFS must be set.

I get that exact error in my dmesg, and as a result /sys/class/rtc/rtc0/wakealarm does not exist. And since /proc is apparently deprecated I can't use the old option either.

As far as I can see I have three options:

* Wait for official updated kernel from Arch team and hope it is fixed

* Compile my own kernel

* Use nvram-wakeup or something like that

Any suggestions on what to do? Other options? I would like to avoid recompiling the kernel if possible, but I guess that would be the quickest solution, right? I plan on reading up on ABS anyway

Should I file this as a bug?

Thanks/Johan

Edit: added link to Mythtv wiki

Last edited by infoball (2008-01-28 14:29:39)