[asterisk-users] dahdi_dummy required?

[covici at ccs.covici.com]

Shaun Ruffell <sruffell at digium.com> wrote:

> On Fri, Sep 23, 2011 at 09:30:59AM -0400, covici at ccs.covici.com wrote:
> > Kevin P. Fleming <kpfleming at digium.com> wrote:
> >> On 09/23/2011 02:50 AM, Ishfaq Malik wrote:
> >>> On Thu, 2011-09-22 at 22:19 -0600, Troy Telford wrote:
> >>>>
> >>>> So am I correct in assuming dahdi_dummy isn't needed/useful
> >>>> anymore?
> >>>
> >>> Application MeetMe will not work without it.
> >> 
> >> This is completely incorrect. MeetMe never relied on dahdi_dummy
> >> specifically, it requires DAHDI to have a working timing source.
> >> Yes, at one point dahdi_dummy was available to provide a timing
> >> source if there weren't any DAHDI cards in the system... but it
> >> is no longer necessary. DAHDI is now able to provide timing and
> >> audio mixing using kernel timers using a built-in timer, so there
> >> is no need for a separate module. The ChangeLog entry above is
> >> correct, as of DAHDI 2.4 and later.
> > 
> > So, how do I get this to work -- when I tried to do this, I could
> > get a conference all right, but it would not record the conference
> > till I actually loaded dahdi-dummy -- which seems to be still
> > built.  I am using 9729 out of trunk.
> 
> John,
> 
> As kpfleming said, dahdi_dummy is no longer built by default.
> Revision 9729 you referenced was first released in 2.5.0 which
> definitely does not use dahdi_dummy by default.
> 
> Perhaps you believe you were able to load dahdi_dummy because dahdi
> is aliased to dahdi_dummy and "before" loading it you were using
> confbridge?
> 
> Below you can see how only dahdi is needed for timing and
> conferencing since the timers are processed in the same function
> that handles the conferencing:
> 
> You can modprobe dahdi_dummy but only 'dahdi' is loaded and
> dahdi_test will work fine...
> 
>   # modprobe dahdi_dummy
>   # lsmod | grep dahdi
>   dahdi                 196680  0 
>   crc_ccitt               6337  1 dahdi
>   # dahdi_test -v -c 3
>   Opened pseudo dahdi interface, measuring accuracy...
>   
>   8192 samples in 8191.592 system clock sample intervals (99.995%)
>   8192 samples in 8190.720 system clock sample intervals (99.984%)
>   8192 samples in 8191.288 system clock sample intervals (99.991%)
>   --- Results after 3 passes ---
>   Best: 99.995 -- Worst: 99.984 -- Average: 99.990234, Difference: 99.990233
> 
> But you can do the same thing only by loading dahdi and not
> dahdi_dummy...
> 
>   # modprobe -r dahdi
>   # lsmod | grep dahdi
>   # dahdi_test
>   Unable to open dahdi interface: No such file or directory
>   # modprobe dahdi
>   # dahdi_test -v -c2
>   Opened pseudo dahdi interface, measuring accuracy...
> 
>   8192 samples in 8199.624 system clock sample intervals (100.093%)
>   8192 samples in 8182.688 system clock sample intervals (99.886%)
>   --- Results after 2 passes ---
>   Best: 99.907 -- Worst: 99.886 -- Average: 99.896633, Difference: 99.989697
> 
> DAHDI will still use the timing from an installed card if available,
> but now it is smart enough to detect if there is not a card
> installed or operating properly and still provide timing without
> requiring the user to load "dahdi_dummy" explicitly.

You are correct, when meetme didn't work, I did not even load dahdi at
all -- that was the confusion.   I am surprised that the modprobe of
dahdi-dummy even succeeds, but I guess it does not matter.

-- 
Your life is like a penny.  You're going to lose it.  The question is:
How do
you spend it?

         John Covici
         covici at ccs.covici.com