README: document initialization

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
This commit is contained in:
Tzafrir Cohen 2013-12-30 14:38:49 +02:00
parent d96be70986
commit 2d3580a3db

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README
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@ -212,6 +212,128 @@ that is included in the ppp/ subdirectory. To install it:
CONFIG_HDLC .
Initialization
--------------
This section documents the start up sequence of the DAHDI modules.
There are generally two options: explicit (using an init script) and
implicit (run from UDEV hook scripts).
Explicit
~~~~~~~~
The dahdi init scripts does the following tasks:
* Loading the module dahdi and any other module listed in
/etc/dahdi/modules.
* For xpp (Astribanks) - some specific initializations. See
README.Astribank.
* Runs link:doc/dahdi_cfg.8.html[dahdi_cfg] after all modules were
loaded.
* A number of other tools may need to be run:
** link:doc/fxotune.8.html[fxotune]
** dahdihpec_enable
Only at this point Asterisk (or any other user of DAHDI) can be run.
Implicit
~~~~~~~~
(Also known as "hot-plug" or "pinned-spans". This requires:
* dahdi >= 2.8.0
* Setting the module parameter auto_assign_spans of dahdi to 0
* (Recommended) Asterisk >= 12 - which supports "dahdi create channels".
When a device driver of a DAHDI device finishes initialization, it
creates a dahdi_device kernel object. A dahdi_device represents a single
DAHDI device (such as a PCI card) and may have several spans. If the
value of auto_assign_spans is 1 when dahdi_device is created, spans are
assigned automatically - each new span gets the first available span
number and range of channels. However if it is set to 0, spans will not
get assigned, and user space programs need to assign them. The
low-level interface for doing so is explained in the section "Span
Assignment" in the README of DAHDI-Linux.
New Devices
^^^^^^^^^^^
When a kernel object is created or destroyed, the kernel sends an event
to user space. Those events are normally handled by udevd. Configurations
for udevd ("udev rules") may be placed in /etc/udev/rules.d or
/lib/udev/rules.d. This package installs rules that instruct udevd to
run the script `/usr/share/dahdi/dahdi_handle_device` on each new
device. This script will:
* If `/etc/dahdi/span-types.conf` exists, apply it to the device. It is
used for E1/T1/J1 settings. See
<<_sample_span_types_conf,sample span-types.conf>>.
* If `/etc/dahdi/assigned-spans.conf` exists, assign the span according
to it (if it is not specified there: don't assign it).
used for E1/T1/J1 settings. See
<<_sample_assigned_spans_conf,sample assigned-spans.conf>>.
* But if that file does not exist, assign the span to the first
available place.
This script mainly uses the commands
link:doc/dahdi_span_types.8.html[dahdi_span_types] and
link:doc/dahdi_span_assignments.8.html[dahdi_span_assignments].
DAHDI devices are listed under `/sys/bus/dahdi_devices/devices`.
If you want to disable running this script, add the following line to
`/etc/dahdi/init.conf`:
.............................
DAHDI_UDEV_DISABLE_DEVICES=yes
.............................
New Spans
^^^^^^^^^
Once a span is assigned, a kernel object will appear for it. It will be
listed under its device. As a new kernel object was created, an event is
sent to udev.
The standard DAHDI udev rules instruct udevd to run the script
`/usr/share/dahdi/dahdi_span_config`. This script configures the new
span:
* If system.conf does not exist, generates a temporary configuration
for the span using link:doc/dahdi_genconf.8.html[dahdi_genconf
system].
* Runs link:doc/dahdi_cfg.8.html[dahdi_cfg] on the new span (using `-S`
and -C`).
* Runs `asterisk -rx 'dahdi create channels'` to add the new channels
and spans to Asterisk (if they were configured in advance).
If you want to disable running this script, add the following line to
`/etc/dahdi/init.conf`:
.............................
DAHDI_UDEV_DISABLE_SPANS=yes
.............................
New Channels
^^^^^^^^^^^^
DAHDI channels have their own representation in the kernel. The standard
udev rules that dahdi-tools includes for them, however, don't run a
script for each device. Each DAHDI channel creates a block device file
at /dev/dahdi/chan/'span'/'rel-chan', where 'span' and 'rel-chan' are
each three-digit numbers (e.g: 035). 'span' is the span number and
'rel-chan' is the channel number relative to the span.
The udev rules generate the following extra symlinks under /dev/dahdi:
* /dev/dahdi/'num' - the channel number. As it was originally (but
continues beyond 250).
* /dev/dahdi/devices/'hardware_id'/'rel-span'/'rel-chan' - if the DAHDI
device has a hardware ID field, provide listing of the device's span
and channels.
* /dev/dahdi/devices/@'hardware_id'/'rel-span'/'rel-chan' - likewise for
the connector field. It has a "@" prefix.
include::UPGRADE.txt[]