isdninfo - ISDN status device
/dev/isdninfo is a character device with major number 45 and minor number 255. It delivers status information from the Linux ISDN subsystem to user level.
When reading from this device, the current status of the Linux ISDN subsystem is delivered in 6 lines of text. Each line starts with a tag string followed by a colon and whitespace. After that the status values are appended separated by whitespace. idmap is the tag of the first line. In this line for every virtual channel, the Id-string of the corresponding lowlevel driver is shown. If no driver is loaded, a - (hyphen) is shown. chmap is the tag of line 2. In this line for every virtual channel, the channel number of the corresponding lowlevel driver is shown. If no driver is loaded, -1 is shown. drmap is the tag of line 3. In this line for every virtual channel, the index number of the corresponding lowlevel driver is shown. If no driver is loaded, -1 is shown. usage is the tag of line 4. In this line for every virtual channel, the current usage is shown. The following usage constants are defined: ISDN_USAGE_NONE (0) Unused channel ISDN_USAGE_RAW (1) Channel used by raw device (currently unsupported) ISDN_USAGE_MODEM (2) Channel used by some ttyI ISDN_USAGE_NET (3) Channel used by an ISDN net-interface ISDN_USAGE_VOICE (4) Channel used by some ttyI in voice mode. ISDN_USAGE_EXCLUSIVE (64) Channel exclusively preserved for a net-interface. This value is logically or'ed with one of the other codes. ISDN_USAGE_OUTGOING (128) Channel is used outgoing. This value is logically or'ed with one of the other codes. It is set, when dialling is started and reset, when either dialling failed or after hangup. Therefore, it is not always an indicator for an established connection. To get a reliable indicator for an established connection, the driver flags (see below) have to be inspected also. flags is the tag of line 5. In this line for every driver slot, it's B-Channel status is shown. If no driver is registered in a slot, a ? is shown. For every established B-Channel of the driver, a bit is set in the shown value. The driver's first channel is mapped to bit 0, the second channel to bit 1 and so on. phone is the tag of line 6. In this line for every virtual channel, the remote phone number is shown if the channel is active. A ??? is shown, if the channel is inactive.
After opening the device, at most 6 lines can be read by a user process. After that, the user process is blocked. Whenever a status change happens, the process is allowed to read 6 more lines, starting with line one.
Currently, there are two ioctl calls supported: IIOCGETDVR Get Revision information. Returns an unsigned long value v, representing various user level interface revisions, where (v & 0xff) is the revision of the modem-register info, available via ioctl on /dev/isdnctrl. ((v >> 8) & 0xff) is the revision of the net-interface config data, available via ioctl on /dev/isdnctrl. and ((v >> 16) & 0xff) is the revision of the data delivered via /dev/isdninfo itself. IIOCGETCPS Get transfer statistics. Returns the number of bytes transferred so far for all virtual channels. The third parameter should be a pointer to an array of unsigned long of size ISDN_MAX_CHANNELS * 2. This array is filled with the byte counter values upon return.
There are some more useful constants defined in /usr/include/linux/isdn.h: ISDN_TTY_MAJOR The major device number of /dev/ttyI. ISDN_TTYAUX_MAJOR The major device number of /dev/cui. ISDN_MAJOR The major device number of /dev/isdnctrl, /dev/isdninfo, /dev/ippp and /dev/isdn ISDN_MAX_DRIVERS The number of driver slots. ISDN_MAX_CHANNELS The number of virtual channels. ISDN_MINOR_CTRL The minor device number of /dev/isdnctrl0. ISDN_MINOR_CTRLMAX The minor device number of /dev/isdnctrl63. ISDN_MINOR_PPP The minor device number of /dev/ippp0. ISDN_MINOR_PPPMAX The minor device number of /dev/ippp64. ISDN_MINOR_STATUS The minor device number of /dev/isdninfo. Other constants, necessary for ioctl's on /dev/isdnctrl are listed in isdnctrl(4).
Fritz Elfert <firstname.lastname@example.org>
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