README: document initialization
Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
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Tzafrir Cohen
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README
122
README
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@ -212,6 +212,128 @@ that is included in the ppp/ subdirectory. To install it:
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CONFIG_HDLC .
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Initialization
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--------------
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This section documents the start up sequence of the DAHDI modules.
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There are generally two options: explicit (using an init script) and
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implicit (run from UDEV hook scripts).
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Explicit
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~~~~~~~~
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The dahdi init scripts does the following tasks:
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* Loading the module dahdi and any other module listed in
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/etc/dahdi/modules.
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* For xpp (Astribanks) - some specific initializations. See
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README.Astribank.
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* Runs link:doc/dahdi_cfg.8.html[dahdi_cfg] after all modules were
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loaded.
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* A number of other tools may need to be run:
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** link:doc/fxotune.8.html[fxotune]
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** dahdihpec_enable
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Only at this point Asterisk (or any other user of DAHDI) can be run.
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Implicit
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~~~~~~~~
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(Also known as "hot-plug" or "pinned-spans". This requires:
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* dahdi >= 2.8.0
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* Setting the module parameter auto_assign_spans of dahdi to 0
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* (Recommended) Asterisk >= 12 - which supports "dahdi create channels".
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When a device driver of a DAHDI device finishes initialization, it
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creates a dahdi_device kernel object. A dahdi_device represents a single
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DAHDI device (such as a PCI card) and may have several spans. If the
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value of auto_assign_spans is 1 when dahdi_device is created, spans are
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assigned automatically - each new span gets the first available span
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number and range of channels. However if it is set to 0, spans will not
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get assigned, and user space programs need to assign them. The
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low-level interface for doing so is explained in the section "Span
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Assignment" in the README of DAHDI-Linux.
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New Devices
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^^^^^^^^^^^
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When a kernel object is created or destroyed, the kernel sends an event
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to user space. Those events are normally handled by udevd. Configurations
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for udevd ("udev rules") may be placed in /etc/udev/rules.d or
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/lib/udev/rules.d. This package installs rules that instruct udevd to
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run the script `/usr/share/dahdi/dahdi_handle_device` on each new
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device. This script will:
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* If `/etc/dahdi/span-types.conf` exists, apply it to the device. It is
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used for E1/T1/J1 settings. See
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<<_sample_span_types_conf,sample span-types.conf>>.
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* If `/etc/dahdi/assigned-spans.conf` exists, assign the span according
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to it (if it is not specified there: don't assign it).
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used for E1/T1/J1 settings. See
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<<_sample_assigned_spans_conf,sample assigned-spans.conf>>.
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* But if that file does not exist, assign the span to the first
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available place.
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This script mainly uses the commands
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link:doc/dahdi_span_types.8.html[dahdi_span_types] and
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link:doc/dahdi_span_assignments.8.html[dahdi_span_assignments].
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DAHDI devices are listed under `/sys/bus/dahdi_devices/devices`.
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If you want to disable running this script, add the following line to
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`/etc/dahdi/init.conf`:
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.............................
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DAHDI_UDEV_DISABLE_DEVICES=yes
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.............................
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New Spans
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^^^^^^^^^
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Once a span is assigned, a kernel object will appear for it. It will be
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listed under its device. As a new kernel object was created, an event is
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sent to udev.
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The standard DAHDI udev rules instruct udevd to run the script
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`/usr/share/dahdi/dahdi_span_config`. This script configures the new
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span:
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* If system.conf does not exist, generates a temporary configuration
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for the span using link:doc/dahdi_genconf.8.html[dahdi_genconf
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system].
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* Runs link:doc/dahdi_cfg.8.html[dahdi_cfg] on the new span (using `-S`
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and -C`).
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* Runs `asterisk -rx 'dahdi create channels'` to add the new channels
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and spans to Asterisk (if they were configured in advance).
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If you want to disable running this script, add the following line to
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`/etc/dahdi/init.conf`:
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.............................
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DAHDI_UDEV_DISABLE_SPANS=yes
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.............................
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New Channels
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^^^^^^^^^^^^
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DAHDI channels have their own representation in the kernel. The standard
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udev rules that dahdi-tools includes for them, however, don't run a
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script for each device. Each DAHDI channel creates a block device file
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at /dev/dahdi/chan/'span'/'rel-chan', where 'span' and 'rel-chan' are
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each three-digit numbers (e.g: 035). 'span' is the span number and
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'rel-chan' is the channel number relative to the span.
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The udev rules generate the following extra symlinks under /dev/dahdi:
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* /dev/dahdi/'num' - the channel number. As it was originally (but
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continues beyond 250).
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* /dev/dahdi/devices/'hardware_id'/'rel-span'/'rel-chan' - if the DAHDI
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device has a hardware ID field, provide listing of the device's span
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and channels.
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* /dev/dahdi/devices/@'hardware_id'/'rel-span'/'rel-chan' - likewise for
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the connector field. It has a "@" prefix.
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include::UPGRADE.txt[]
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