[asterisk-users] dahdi_dummy required?

[Shaun Ruffell]

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.

-- 
Shaun Ruffell
Digium, Inc. | Linux Kernel Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: www.digium.com & www.asterisk.org