DAHDI Telephony Interface Driver ================================= Asterisk Development Team $Revision: 8341 $, $Date: 2010-03-16 02:24:48 +0600 (вт, 16 мар 2010) $ DAHDI stands for Digium Asterisk Hardware Device Interface. This package contains the kernel modules for DAHDI. For the required userspace tools see the package dahdi-tools. FreeBSD Notes ------------- FreeBSD port is maintained by Max Khon Drop me an e-mail if you have hardware that is supported by dahdi-linux but is not supported on FreeBSD. Building ~~~~~~~~ Run "make", then "make install" in the root directory. Supported drivers ~~~~~~~~~~~~~~~~~ The following drivers are currently supported on FreeBSD: - main DAHDI driver - dahdi_echocan_jpah - dahdi_echocan_kb1 - dahdi_echocan_mg2 - dahdi_echocan_sec - dahdi_echocan_sec2 - dahdi_dummy - dahdi_dynamic - dahdi_dynamic_loc - dahdi_dynamic_eth and dahdi_dynamic_ethmf - wcb4xxp - wct4xxp, including HW echo cancellation support (Octasic) - wctdm24xxp Additional notes ~~~~~~~~~~~~~~~~ TDMoE (dahdi_dynamic_eth and dahdi_dynamic_ethmf) drivers require ng_ether kernel module to be loaded. Credits ~~~~~~~ main DAHDI driver and wcb4xxp FreeBSD port sponsored by Ethon Technologies GmbH, http://ethon.de/ dahdi_dynamic and eth/ethmf FreeBSD port sponsored by Redfone Communications, LLC, http://red-fone.com/ 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 - wcb4xxp: * Digium B410: PCI quad-port BRI - 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/AEX410: up to 4 analog ports * Digium Hx8 Series: Up to 8 analog or BRI 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. Installation ------------ If all is well, you just need to run the following: make make install You'll need the utilities provided in the package dahdi-tools to configure DAHDI devices on your system. If using `sudo` to build/install, you may need to add /sbin to your PATH. If you still have problems, read further. Build Requirements ~~~~~~~~~~~~~~~~~~ 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. TODO: copy build requirement from Zaptel README. Installing 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 the 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 Extra Modules ~~~~~~~~~~~~~ To build extra modules / modules directory not included in the DAHDI distribution, use the optional variables MODULES_EXTRA and SUBDIRS_EXTRA: make MODULES_EXTRA="mod1 mod2" make MODULES_EXTRA="mod1 mod2" SUBDIRS_EXTRA="subdir1/ subdir1/" Static Device Files ~~~~~~~~~~~~~~~~~~~ Userspace programs communicate with the DAHDI modules through special device files under /dev/dahdi . Those are normally created by udev, but if you use an embedded-type system and don't wish to use udev, you can generate them with the following script, from the source directory: ./build_tools/make_static_devs This will generate the device files under /dev/dahdi . If you need to generate them elsewhere (e.g. `tmp/newroot/dev/dahdi`) use the option -d to the script: ./build_tools/make_static_devs -d tmp/newroot/dev/dahdi Installing the B410P drivers with mISDN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DAHDI includes the wcb4xxp driver for the B410P, however, support for the B410P was historically provided by mISDN. If you would like to use the mISDN driver with the B410P, please comment out the wcb4xxp line in /etc/dahdi/modules. This will prevent DAHDI from loading wcb4xxp which will conflict with the mISDN driver. To install the mISDN driver for the B410P, please see http://www.misdn.org for more information, but the following sequence of steps is roughly equivalent to 'make b410p' from previous releases. wget http://www.misdn.org/downloads/releases/mISDN-1_1_8.tar.gz wget http://www.misdn.org/downloads/releases/mISDNuser-1_1_8.tar.gz tar xfz mISDN-1_1_8.tar.gz tar xfz mISDNuser-1_1_8.tar.gz pushd mISDN-1_1_8 make install popd pushd mISDNuser-1_1_8 make install popd /usr/sbin/misdn-init config You will then also want to make sure /etc/init.d/misdn-init is started automatically with either 'chkconfig --add misdn-init' or 'update-rc.d misdn-init defaults 15 30' depending on your distribution. NOTE: At the time this was written, misdn-1.1.8 is not compatible the 2.6.25 kernel. Please use a kernel version 2.6.25 or earlier. OSLEC ~~~~~ http://www.rowetel.com/ucasterisk/oslec.html[OSLEC] is an Open Source Line Echo Canceller. It is currently in the staging subtree of the mainline kernel and will hopefully be fully merged at around version 2.6.29. The echo canceller module dahdi_echocan_oslec provides a DAHDI echo canceller module that uses the code from OSLEC. As OSLEC has not been accepted into mainline yet, its interface is not set in stone and thus this driver may need to change. Thus it is not built by default. Luckily the structure of the dahdi-linux tree matches that of the kernel tree. Hence you can basically copy drivers/staging/echo and place it under driver/staging/echo . In fact, dahdi_echocan_oslec assumes that this is where the oslec code lies. If it is elsewhere you'll need to fix the #include line. Thus for the moment, the simplest way to build OSLEC with dahdi is: 1. Copy the directory `drivers/staging/echo` from a recent kernel tree (at least 2.6.28-rc1) to the a subdirectory with the same name in the dahdi-linux tree. 2. Edit drivers/dahdi/Kbuild and uncomment the two lines related to OSLEC. After doing that, you'll see the following when building (running 'make') ... CC [M] /home/tzafrir/dahdi-linux/drivers/dahdi/dahdi_echocan_oslec.o CC [M] /home/tzafrir/dahdi-linux/drivers/dahdi/../staging/echo/echo.o ... As this is an experimental driver, problems building and using it should be reported on the https://lists.sourceforge.net/lists/listinfo/freetel-oslec[OSLEC mailing list]. Live Install ~~~~~~~~~~~~ In many cases you already have DAHDI installed on your system but would like to try a different version. E.g. in order to check if the latest version fixes a bug that your current system happens to have. DAHDI-linux includes a script to automate the task of installing DAHDI to a subtree and using it instead of the system copy. Module loading through modprobe cannot be used. Thus the script pre-loads the required modules with insmod (which requires some quesswork as for which modules to load). It also sets PATH and other environment variables to make all the commands do the right thing. There is an extra mode of operation to copy all the required files to a remote host and run things there, for those who don't like to test code on thir build system. Live Install: The Basics ^^^^^^^^^^^^^^^^^^^^^^^^ Basic operation is through running ./build_tools/live_dahdi from the root directory of the dahdi-linux tree. Using DAHDI requires dahdi-tools as well, and the script builds and installs dahdi-tools. By default it assumes the tree of dahdi-tools is in the directory 'dahdi-tools' alongside the dahdi-linux tree. If you want to checkout the trunks from SVN, use: svn checkout http://svn.asterisk.org/svn/dahdi/linux/trunk dahdi-linux svn checkout http://svn.asterisk.org/svn/dahdi/tools/trunk dahdi-tools cd dahdi-linux If the tools directory resides elsewhere, you'll need to edit live/live.conf (see later on). The usage message of live_dahdi: Usage: equivalent of: live_dahdi configure ./configure live_dahdi install make install live_dahdi config make config live_dahdi unload /etc/init.d/dahdi stop live_dahdi load /etc/init.d/dahdi start live_dahdi reload /etc/init.d/dahdi restart live_dahdi xpp-firm (Reset and load xpp firmware) live_dahdi rsync TARGET (copy filea to /tmp/live in host TARGET) live_dahdi exec COMMAND (Run COMMAND in 'live' environment) Normally you should run: ./build_tools/live_dahdi configure ./build_tools/live_dahdi install ./build_tools/live_dahdi config to build and install everything. Up until now no real change was done. This could actually be run by a non-root user. All files are installed under the subdirectory live/ . Reloading the modules (and restarting Asterisk) is done by: ./build_tools/live_dahdi reload Note: this stops Asterisk, unloads the DAHDI modules, loads the DAHDI modules from the live/ subdirectory, configures the system and re-starts Asterisk. This *can* do damage to your system. Furthermore, the DAHDI configuration is generated by dahdi_genconf. It can be influenced by a genconf_parameters file. But it may or may not be what you want. If you want to run a command in the environment of the live system, use the command 'exec': ./build_tools/live_dahdi lsdahdi ./build_tools/live_dahdi dahdi_hardware -v Note however: ./build_tools/live_dahdi dahdi_cfg -c live/etc/dahdi/system.conf Live Install Remote ^^^^^^^^^^^^^^^^^^^ As mentioned above, live_dahdi can also copy all the live system files to a remote system and run from there. This requires rsync installed on both system and assumes you can connect to the remove system through ssh. tzafrir@hilbert $ ./build_tools/live_dahdi rsync root@david root@david's password: /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: character 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 receives 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 purpose. 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 incorporated 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. There are up to 128 spans and 1024 channels. This is a hard-wired limit (see dahdi/user.h . Several places throuout the code assume a channel number fits in a 16 bits number). Channel and span numbers start at 1. Dynamic Spans ~~~~~~~~~~~~~ Dynamic spans are spans that are not represented by real hardware. Currently there are two types of them: tdmoe:: TDM over Ethernet. A remote span is identified by an ethernet (MAC) address. local:: Generates a span that is actually a loopback to a different local span. Modules that support the dynamic spans are typically loaded at the time the ioctl DAHDI_DYNAMIC_CREATE is called. This is typically called by dahdi_cfg when it has a line such as: dynamic,somename,params in /etc/dahdi/system.conf . In that case it will typically try to load (through modprobe) the modules dahdi_dynamic and dahdi_dynamic_'somename'. It will then pass 'params' to it. Dynamic spans are known to be tricky and are some of the least-tested parts of DAHDI. Echo Cancellers ~~~~~~~~~~~~~~~ (To be documented later) Tone Zones ~~~~~~~~~~ (To be documented later) 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 alarms 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) User-space Interface ~~~~~~~~~~~~~~~~~~~~ User-space programs can only work with DAHDI channels. The basic operation is 'read()' to read audio from the device and write() to write audio to it. Audio can be encoded as either alaw (G.711a) or (m)ulaw (G.711u). See the ioctl DAHDI_SETLAW. While it is technically possible to use /dev/dahdi/NUMBER directly, this will only work for channel numbers up to 249. Generally you should use: int channo = CHAN_NUMBER_TO_OPEN; int rc; int fd = open("/dev/dahdi/channel", O_RDRW, 0600); // Make sure fd >= 0 rc = ioctl(fd, DAHDI_SPECIFY, &channo) < 0); // Make sure this rc >= 0 FIXME: there's more to tell about the user-space interface. Configuration ~~~~~~~~~~~~~ Most of the configuration is applied from userspace using the tool 'dahdi_cfg' in the package dahdi_tools. This section will not cover the specifics of that file. Rather it will cover the way configuration from this file is applied. Also note that there are other methods to configure DAHDI drivers: there are <<_module_parameters,Module Parameters>>. The xpp driver have their own separate initialization scripts and xpp.conf that arecovered in README.Astribank. When a span is registered, it is considered "unconfigured". Only after dahdi_cfg has been run to apply configuration, the span is ready to run. The only exception to that is 'dahdi_dummy', which does not need any configuration. Some of the configuration is handled by the DAHDI core. Some of it is handled by callbacks, which are function pointers in the `struct dahdi_span': 'spanconfig', 'chanconfig' and (in a way) 'startup'. Dahdi_cfg starts by reading the configuration from the configuration file ('/etc/dahdi/system.conf', by default), and creating a local configuration to apply. If you use -v, at this stage it will pront the configuration that is "about to be configured". Then it will start to actually apply the configuration. Before actually applying configuration, it destroys any existing <<_dynamic_spans,dynamic spans>> and generates new ones (if so configured. FIXME: what about running DAHDI_SPANCONFIG for new dynamic spans?). Next thing it will do is apply the parameters from *span* lines using the ioctl DAHDI_SPANCONFIG. Some generic processing of parameters passed in DAHDI_SPANCONFIG is done in the DAHDI core, in the callback function spanconfig in , but most of it is left to 'spanconfig' callback of the span (if it exists. This one typically does not exists on analog cards). Now dahdi_cfg will ask each existing channel for its existing configuration and apply configuration if configuration changes are needed. Configuration is applied to the channels using the ioctl call DAHDI_CHANCONFIG ioctl. As in the case of the span configuration, part of it is applied by the DAHDI core, and then it is handed over to the span's chanconfig callback. Typically all spans will have such a callback. <<_echo_cancellers,Echo cancellers>> and <<_tone_zones,tone-zones>> are handled separately later. Once everything is done, the ioctl DAHDI_STARTUP is called for every span. This is also translated to a call to the optional span callback 'startup'. Finally the ioctl DAHDI_HDLC_RATE is called for every channel (that is: if '56k' is not set for the channel, it will be explicitly set to the standard HDLC rate of 64k). Low-Level Drivers ~~~~~~~~~~~~~~~~~ Low-level drivers create spans ('struct dahdi_span'). They register the spans with the DAHDI core using 'dahdi_register()'. 'struct dahdi_span' has a number of informative members that are updated solely by the low-level driver: name:: A concise span name. E.g.: Foo/1 desc:: A slightly longer span name. spantype:: Span type in text form. manufacturer:: Span's device manufacturer devicetype:: Span's device type location:: span device's location in system irq:: IRQ for this span's hardware irqmisses:: Interrupt misses timingslips:: Clock slips There are various function pointers in the struct 'dahdi_span' which are used by the DAHDI core to call the low-level driver. Most of them are optional. The following apply to a span: setchunksize:: FIXME: seems to be unused. spanconfig:: Basic span configuration (called from dahdi_cfg). startup:: Last minute initialization after the configuration was applied. shutdown:: Explicit shutdown (e.g. for dynamic spans). Normally not needed. maint:: Enable/disable maintinance mode (FIXME: document). sync_tick:: Get notified that the master span has ticked. The following apply to a single channel. chanconfig:: Configure the channel (called from dahdi_cfg). open:: Channel was opened for read/write from user-space. close:: Channel was closed by user-space. ioctl:: Handle extra ioctls. Should return -ENOTTY if ioctl is not known to the channel echocan_create:: Create a custom echo canceller. Normally used for providing a hardware echo canceller. If NULL, the standard DAHDI echo canceller modules will be used. rbsbits:: Copy signalling bits to device. See below on signalling. hooksig:: Implement RBS-like signalling-handling. See below on signalling. sethook:: Handle signalling yourself. See below on signalling. hdlc_hard_xmit:: Used to tell an onboard HDLC controller that there is data ready to transmit. audio_notify:: (if DAHDI_AUDIO_NOTIFY is set) - be notified when the channel is (or isn't) in audio mode. Which may mean (for an ISDN B-channel) that its data need not be sent. There are several alternative methods for a span to use for signalling. One of them should be used. Signalling: rbsbits ^^^^^^^^^^^^^^^^^^^ If the device is a CAS interface, the driver should copy the signalling bits to and from the other side, and DAHDI will handle the signalling. The driver just need to provide a 'rbsbits' and set DAHDI_FLAG_RBS in the span->flags. Note that 'rbs' (Robed Bits Signalling) here merely refers to the (up to) 4 signalling bits of the channel. In T1 they are transmitted by "robbing" bits from the channels and hence the name. In E1 they are transmitted in a timeframe of their own. The driver should then signal a change in the signalling bits in a channel using dahdi_rbsbits(). Signalling: hooksig ^^^^^^^^^^^^^^^^^^^ If the device does not know about signalling bits, but has their equivalents (i.e. can disconnect battery, detect off hook, generate ring, etc directly) then the driver can specify a 'sethook' function and set DAHDI_FLAG_RBS in span->flags. In that case DAHDI will call that function whenever the signalling state changes. The hooksig function is only used if the rbsbits function is not set. The span should notify DAHDI of a change of signalling in a channel using dahdi_hooksig(). Signalling: sethook ^^^^^^^^^^^^^^^^^^^ Alternatively, if DAHDI_FLAG_RBS is not set in the flags of the span (to use either rbsbits or hooksig), the DAHDI core will try to call the 'sethook' function of the span (if it exists) to handle individual hook states. The span should then notify DAHDI of a change in the signalling state using dahdi_sethook(). FIXME: anybody using this one? 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 backward-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 specific 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 DAHDI_EXAMPLE _IOWR (DAHDI_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 DAHDI_EXAMPLE_V1 _IOWR (DAHDI_CODE, 62, struct zt_example_v1) #define DAHDI_EXAMPLE _IOWR (DAHDI_CODE, 62, struct zt_example) ------------------------------------ We actually have here two different ioctls: the old DAHDI_EXAMPLE would be 0xC0044A3E . DAHDI_EXAMPLE_V1 would have the same value. But the new value of DAHDI_EXAMPLE would be 0xC0084A3E . (TODO: fix ioctl values) 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 DAHDI_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. Alarm Types ~~~~~~~~~~~ An alarm indicates that a port is not available for some reason. Thus it is probably not a good idea to try to call out through it. Red Alarm ^^^^^^^^^ Your T1/E1 port will go into red alarm when it cannot maintain synchronization with the remote switch. A red alarm typically indicates either a physical wiring problem, loss of connectivity, or a framing and/or line-coding mismatch with the remote switch. When your T1/E1 port loses sync, it will transmit a yellow alarm to the remote switch to indicate that it's having a problem receiving signal from the remote switch. The easy way to remember this is that the R in red stands for "right here" and "receive"... indicating that we're having a problem right here receiving the signal from the remote switch. Yellow Alarm ^^^^^^^^^^^^ (RAI -- Remote Alarm Indication) Your T1/E1 port will go into yellow alarm when it receives a signal from the remote switch that the port on that remote switch is in red alarm. This essentially means that the remote switch is not able to maintain sync with you, or is not receiving your transmission. The easy way to remember this is that the Y in yellow stands for "yonder"... indicating that the remote switch (over yonder) isn't able to see what you're sending. Blue Alarm ^^^^^^^^^^ (AIS -- Alarm Indication Signal) Your T1/E1 port will go into blue alarm when it receives all unframed 1s on all timeslots from the remote switch. This is a special signal to indicate that the remote switch is having problems with its upstream connection. dahdi_tool and Asterisk don't correctly indicate a blue alarm at this time. The easy way to remember this is that streams are blue, so a blue alarm indicates a problem upstream from the switch you're connected to. Recovering from Alarm ^^^^^^^^^^^^^^^^^^^^^ TODO: explain. Loopback ^^^^^^^^ Not really an alarm. Indicates that a span is not available, as the port is in either a local or remote loopback mode. Not Open ^^^^^^^^ Something is not connected. Used by e.g. the drivers of the Astribank to indicate a span that belongs to a device that has been disconnected but is still being used by userspace programs and thus can't e destroyed. 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. Known Issues ------------ KB1 does not function when echocancel > 128 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ KB1 was not designed to function at greater than 128 taps, and if configured this way, will result in the destruction of audio. Ideally DAHDI would return an error when a KB1 echocanceller is configured with greater than 128 taps. Reporting Bugs -------------- Please report bug and patches to the Asterisk bug tracker at http://issues.asterisk.org in the "DAHDI" category. Links ----- - http://asterisk.org/[] - The Asterisk PBX - http://voip-info.org/[] - http://voip-info.org/wiki/view/DAHDI[] - http://docs.tzafrir.org.il/dahdi-linux/README.html[Up-to-date HTML version of this file]