DAHDI Telephony Interface Driver ================================= Asterisk Development Team $Revision: 4728 $, $Date: 2008-08-06 17:15:18 -0500 (Wed, 06 Aug 2008) $ DAHDI stands for Digium Asterisk Hardware Device Interface. Supported Hardware ------------------ Digital Cards ~~~~~~~~~~~~~ - wct4xxp: * Digium TE205P/TE207P/TE210P/TE212P: PCI dual-port T1/E1/J1 * Digium TE405P/TE407P/TE410P/TE412P: PCI quad-port T1/E1/J1 * Digium TE220: PCI-Express dual-port T1/E1/J1 * Digium TE420: PCI-Express quad-port T1/E1/J1 - wcte12xp: * Digium TE120P: PCI single-port T1/E1/J1 * Digium TE121: PCI-Express single-port T1/E1/J1 * Digium TE122: PCI single-port T1/E1/J1 - wcte11xp: * Digium TE110P: PCI single-port T1/E1/J1 - wct1xxp: * Digium T100P: PCI single-port T1 * Digium E100P: PCI single-port E1 - tor2: Tormenta quad-span T1/E1 card from the Zapata Telephony project Analog Cards ~~~~~~~~~~~~ - wctdm24xxp: * Digium TDM2400P/AEX2400: up to 24 analog ports * Digium TDM800P/AEX800: up to 8 analog ports * Digium TDM410P: up to 4 analog ports - wctdm: * Digium TDM400P: up to 4 analog ports - xpp: Xorcom Astribank: a USB connected unit of up to 32 ports (including the digital BRI and E1/T1 modules) - wcfxo: X100P, similar and clones. A simple single-port FXO card Other Drivers ~~~~~~~~~~~~~ - pciradio: Zapata Telephony PCI Quad Radio Interface - wctc4xxp: Digium hardware transcoder cards (also need dahdi_transcode) - dahdi_dynamic_eth: TDM over Ethernet (TDMoE) driver. Requires dahdi_dynamic - dahdi_dynamic_loc: Mirror a local span. Requires dahdi_dynamic - dahdi_dummy: A dummy driver that only provides a DAHDI timing source. Build System ~~~~~~~~~~~~~~ gcc and friends. Generally you will need to install the package gcc. There may be cases where you will need a specific version of gcc to build kernel modules. Installation ~~~~~~~~~~~~ Note: If using `sudo` to build/install, you may need to add /sbin to your PATH. ---------------------------------- # make # make install Building to a Subtree ~~~~~~~~~~~~~~~~~~~~~ The following may be useful when testing the package or when preparing a package for a binary distribution (such as an rpm package) installing onto a subtree rather than on th real system. make install DESTDIR=targetdir This can be useful for any partial install target of the above (e.g: install-modules or install-programs). the targetdir must be an absolute path, at least if you install the modules. To install to a relative path you can use something like: make install-modules DESTDIR=$PWD/target The 'install' target might fail if run as a user to a DESTDIR when attempting to generate device files. In that case, try: make install DESTDIR=$PWD/target DYNFS= Configuration ~~~~~~~~~~~~~ Configuration for DAHDI resides under /etc/dahdi . /etc/dahdi/system.conf ~~~~~~~~~~~~~~~~~~~~~~ The main method to configure DAHDI devices is using the utility *dahdi_cfg*. dahdi_cfg reads data from the configuration file /etc/dahdi/system.conf , figures out what configuration to send to channels, and send it to the kernel. A sample annotated system.conf is included in this directory and installed by default. Edit it to suit your configuration. Alternatively use the script dahdi_genconf to generate one that should work with your system. /etc/dahdi/init.conf ~~~~~~~~~~~~~~~~~~~~ The configuration file of the dahdi init.d script is /etc/dahdi/init.conf . That file is used to override defaults that are set at the beginning of the init.d script. Module Parameters ~~~~~~~~~~~~~~~~~ The kernel modules can be configured through module parameters. Module parameters can optionally be set at load time. They are normally set (if needed) by a line in a file under /etc/modprobe.d/ or in the file /etc/modprobe.conf. Example line: options dahdi debug=1 The module parameters can normally be modified at runtime through sysfs: pungenday:~# cat /sys/module/dahdi/parameters/debug 0 pungenday:~# echo 1 >/sys/module/dahdi/parameters/debug pungenday:~# cat /sys/module/dahdi/parameters/debug 1 Viewing and setting parameters that way is possible as of kernel 2.6 . In kernels older than 2.6.10, the sysfs "files" for the parameters reside directly under /sys/module/'module_name' . Useful module parameters: debug (most modules):: Sets debug mode / debug level. With most modules 'debug' can be either disabled (0, the default value) or enabled (any other value). + + wctdm and wcte1xp print several extra debugging messages if the value of debug is more than 1. + + Some modules have "debugging flags" bits - the value of debug is a bitmask and several messages are printed if some bits are set: - dahdi_dummy: * 1: DEBUG_GENERAL - general error messages. * 2: DEBUG_TICKS - Show that the module is alive :-) - wctdm24xxp: * 1: DEBUG_CARD * 2: DEBUG_ECHOCAN - wct4xxp: * 1: DEBUG_MAIN * 2: DEBUG_DTMF * 4: DEBUG_REGS * 8: DEBUG_TSI * 16: DEBUG_ECHOCAN * 32: DEBUG_RBS * 64: DEBUG_FRAMER - xpp: See also README.Astribank: * 1: GENERAL - General debug comments. * 2: PCM - PCM-related messages. Tend to flood logs. * 4: LEDS - Anything related to the LEDs status control. The driver produces a lot of messages when the option is enabled. * 8: SYNC - Synchronization related messages. * 16: SIGNAL - DAHDI signalling related messages. * 32: PROC - Messages related to the procfs interface. * 64: REGS - Reading and writing to chip registers. Tends to flood logs. * 128: DEVICES - Device instantiation, destruction and such. * 256 - COMMANDS - Protocol commands. Tends to flood logs. deftaps (dahdi):: The default size for the echo canceller. The number is in "taps", that is "samples", 1/8 ms. The default is 64 - for a tail size of 8 ms. + + Asterisk's chan_dahdi tends to pass its own value anyway, with a different default size. So normally setting this doesn't change anything. To get a list of parameters supported by a module, use modinfo module_name Or, for a module you have just built: modinfo ./module_name.ko For the xpp modules this will also include the description and default value of the module. You can find a list of useful xpp module parameters in README.Astribank . Internals --------- DAHDI Device Files ~~~~~~~~~~~~~~~~~~~ Userspace programs will usually interact with DAHDI through device files under the /dev/dahdi directory (pedantically: characted device files with major number 196) . Those device files can be generated statically or dynamically through the udev system. * /dev/dahdi/ctl (196:0) - a general device file for various information and control operations on the DAHDI channels. * /dev/dahdi/NNN (196:NNN) - for NNN in the range 1-249. A device file for DAHDI channel NNN. It can be used to read data from the channel and write data to the channel. * /dev/dahdi/transcode (196:250) - Used to connect to a DAHDI transcoding device. * /dev/dahdi/timer (196:253) - Allows setting timers. Used anywhere? * /dev/dahdi/channel (196:254) - Can be used to open an arbitrary DAHDI channel. This is an alternative to /dev/dahdi/NNN that is not limited to 249 channels. * /dev/dahdi/pseudo (196:255) - A timing-only device. Every time you open it, a new DAHDI channel is created. That DAHDI channel is "pseudo" - DAHDI recieves no data in it, and only sends garbage data with the same timing as the DAHDI timing master device. DAHDI Timing ~~~~~~~~~~~~~ A PBX system should generally have a single clock. If you are connected to a telephony provider via a digital interface (e.g: E1, T1) you should also typically use the provider's clock (as you get through the interface). Hence one important job of Asterisk is to provide timing to the PBX. DAHDI "ticks" once per millisecond (1000 times per second). On each tick every active DAHDI channel reads and 8 bytes of data. Asterisk also uses this for timing, through a DAHDI pseudo channel it opens. However, not all PBX systems are connected to a telephony provider via a T1 or similar connection. With an analog connection you are not synced to the other party. And some systems don't have DAHDI hardware at all. Even a digital card may be used for other uses or is simply not connected to a provider. DAHDI cards are also capable of providing timing from a clock on card. Cheap x100P clone cards are sometimes used for that pupose. If all the above fail, you can use the module dahdi_dummy to provide timing alone without needing any DAHDI hardware. It will work with most systems and kernels. You can check the DAHDI timing source with dahdi_test, which is a small utility that is included with DAHDI. It runs in cycles. In each such cycle it tries to read 8192 bytes, and sees how long it takes. If DAHDI is not loaded or you don't have the device files, it will fail immediately. If you lack a timing device it will hang forever in the first cycle. Otherwise it will just give you in each cycle the percent of how close it was. Also try running it with the option -v for a verbose output. To check the clock source that is built into dahdi_dummy, you can either look at title of its span in /proc/dahdi file for a "source:" in the description. Or even run: strings dahdi.ko | grep source: Spans and Channels ~~~~~~~~~~~~~~~~~~ DAHDI provides telephony *channels* to the userspace applications. Those channels are channels are incorperated into logical units called *spans*. With digital telephony adapters (e.g: E1 or T1), a span normally represents a single port. With analog telephony a span typically represents a PCI adapter or a similar logical unit. Both channels and spans are identified by enumerating numbers (beginning with 1). The number of the channel is the lowest unused one when it is generated, and ditto for spans. PROCFS Interface: /proc/dahdi ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A simple way to get the current list of spans and channels each span contains is the files under /proc/dahdi . /proc/dahdi is generated by DAHDI as it loads. As each span registers to DAHDI, a file under /proc/dahdi is created for it. The name of that file is the number of that span. Each file has a 1-line title for the span followed by an empty line and then a line for each channel of the span. The title line shows the number of the span, its name and title, and (potentially) the alarms in which it is. The title shows the span number and name, followed by any allarms the span may have: For example, here is the first span in my system (with no alarms): Span 1: XBUS-00/XPD-00 "Xorcom XPD #0/0: FXS" The channel line for each channel shows its channel number, name and the actual signalling assigned to it through dahdi_cfg. Before being configured by dahdi_cfg: This is DAHDI channel 2, whose name is 'XPP_FXS/0/0/1'. 2 XPP_FXS/0/0/1 After being configured by dahdi_cfg: the signalling 'FXOLS' was added. FXS channels have FXO signalling and vice versa: 2 XPP_FXS/0/0/1 FXOLS If the channel is in use (typically opened by Asterisk) then you will see an extra '(In use)': 2 XPP_FXS/0/0/1 FXOLS (In use) ABI Compatibility ~~~~~~~~~~~~~~~~~ Like any other kernel code, DAHDI strives to maintain a stable interface to userspace programs. The API of DAHDI to userspace programs, dahdi/user.h, has remained backword-compatible for a long time and is expected to remain so in the future. With the ABI (the bits themselves) things are slightly trickier. DAHDI's interface to userspace is mostly ioctl(3) calls. Ioctl calls are identified by a number that stems from various things, one of which is the size of the data structure passed between the kernel and userspace. Many of the DAHDI ioctl-s use some sepcific structs to pass information between kernel and userspace. In some cases the need arose to pass a few more data members in each call. Simply adding a new member to the struct would have meant a new number for the ioctl, as its number depends on the size of the data passed. Thus we would add a new ioctl with the same base number and with the original struct. So suppose we had the following ioctl: ---------------------------------- struct zt_example { int sample; } #define ZT_EXAMPLE _IOWR (ZT_CODE, 62, struct zt_example) ---------------------------------- And we want to add the field 'int onemore', we won't just add it to the struct. We will do something that is more complex: ------------------------------------ /* The original, unchanged: */ struct zt_example_v1 { int sample; } /* The new struct: */ struct zt_example { int sample; int onemore; } #define ZT_EXAMPLE_V1 _IOWR (ZT_CODE, 62, struct zt_example_v1) #define ZT_EXAMPLE _IOWR (ZT_CODE, 62, struct zt_example) ------------------------------------ We actually have here two different ioctls: the old ZT_EXAMPLE would be 0xC0044A3E . ZT_EXAMPLE_V1 would have the same value. But the new value of ZT_EXAMPLE would be 0xC0084A3E . Programs built with the original dahdi/user.h (before the change) use the original ioctl, whether or not the kernel code is actually of the newer version. Thus in most cases there are no compatibility issues. When can we have compatibility issues? If we have code built with the new dahdi/user.h, but the loaded kernel code (modules) are of the older version. Thus the userspace program will try to use the newer ZT_EXAMPLE (0xC0084A3E). But the kernel code has no handler for that ioctl. The result: the error 25, ENOTTY, which means "Inappropriate ioctl for device". As a by-product of that method, for each interface change a new #define is added. That definition is for the old version and thus it might appear slightly confusing in the code, but it is useful for writing code that works with all versions of DAHDI. License ------- This package is distributed under the terms of the GNU General Public License Version 2, except for some components which are distributed under the terms of the GNU Lesser General Public License Version 2.1. Both licenses are included in this directory, and each file is clearly marked as to which license applies. If you wish to use the DAHDI drivers in an application for which the license terms are not appropriate (e.g. a proprietary embedded system), licenses under more flexible terms can be readily obtained through Digium, Inc. at reasonable cost. Reporting Bugs -------------- Please report bug and patches to the Asterisk bug tracker at http://bugs.digium.com in the "DAHDI" category. Links ----- - http://asterisk.org/[] - The Asterisk PBX - http://voip-info.org/[] - http://voip-info.org/wiki/view/Asterisk+Zaptel+Installation[] - http://docs.tzafrir.org.il/dahdi/README.html[Up-to-date HTML version of this file]