[asterisk-users] dahdi_dummy: Unable to register DAHDI rtc driver

[David Backeberg]

On Wed, Apr 8, 2009 at 10:23 AM, Shaun Ruffell <sruffell at digium.com> wrote:
> David Backeberg wrote:
>> Hello there:
>>
>> I think I have a silly kernel configuration problem. I'm running:
>> * vanilla 2.6.27.10 kernel built from source
>> * dahdi-2.1.0.4 built from source
>>
>> So far so good,
>> dahdi module loads just fine:
>> dahdi: Telephony Interface Registered on major 196
>> dahdi: Version: 2.1.0.4
>>
>> when I try to:
>> hal04 dahdi # modprobe dahdi_dummy
>> FATAL: Error inserting dahdi_dummy
>> (/lib/modules/2.6.27.10/dahdi/dahdi_dummy.ko): Input/output error
>>
>> kernel messages gives me:
>> dahdi_dummy: Unable to register DAHDI rtc driver
>>
> There is a kernel config parameter called CONFIG_HPET_EMULATE_RTC, that
> if defined in the kernel config, will cause the behavior that you're
> seeing.  I have not looked to see at which version that option came in.
>
> However, I think support for RTC in dahdi_dummy is best dropped.  There
> is a patch on mantis (http://bugs.digium.com/view.php?id=13930) against
> dahdi_dummy that allows it to provide accurate timing with standard
> kernel timers that you may want to try.

I applied the patch on Bug 13930, tested it out and it has been a
great success. I now see that the Bug has been closed and the patch
has been added to DAHDI trunk. Hooray!

As a piece of documentation, I now get a different report from
dahdi_tool when using dahdi_dummy. dahdi_tool used to report that the
source was RTC. Now the source is Linux26. The "dahdi_test -c 20"
results were much more consistent with Bug 13930's patch than when
using RTC as the timing source using my 2.6.25.9 kernel.