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
Channel used by raw device (currently unsupported)
Channel used by some ttyI
Channel used by an ISDN net-interface
Channel used by some ttyI in voice mode.
Channel exclusively preserved for a net-interface. This
value is logically or’ed with one of the other codes.
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:
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
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
The major device number of /dev/ttyI.
The major device number of /dev/cui.
The major device number of /dev/isdnctrl, /dev/isdninfo,
/dev/ippp and /dev/isdn
The number of driver slots.
The number of virtual channels.
The minor device number of /dev/isdnctrl0.
The minor device number of /dev/isdnctrl63.
The minor device number of /dev/ippp0.
The minor device number of /dev/ippp64.
The minor device number of /dev/isdninfo.
Other constants, necessary for ioctl’s on /dev/isdnctrl are listed in
Fritz Elfert <email@example.com>