Hardware drivers

A vISDN low-level driver interfaces the vISDN infrastructure to a real ISDN line.

Once loaded, a vISDN driver register every resource provided by each device it finds to the core infrastructure. Currently resources may be ports and channels.

Ports are typically:

S/T or U basic rate interfaces
E1 primary rate interfaces
PCM interface to a hardware TDM bus

Each port is comprised of several channels each of them may play a specifici role:

D channel for signalling
E channel for signalling echo (BRI only)
B channel for general purpose
S/Q channels for TE<=>NT-1 communication

Hardware drivers make exensive use of the sysfs filesystem to export internal parameters to userspace.

Just like any other PCI device, a vISDN PCI adapter will have a device entry in the /sys/bus/pci/devices/ directory. Analogously a USB device will have its entry in /sys/bus/usb/devices/.

Among the usual parameters, vISDN devices create other attributes and subdevices. A typical tree may look like:

/sys/bus/pci/devices/0000:00:09.0/
|-- 11
|   |-- i11.B1
|   |   |-- bitorder
|   |   |-- bus -> ../../../../../bus/visdn
|   |   |-- detach_state
|   |   |-- flags
|   |   |-- framing
|   |   |-- port_name
|   |   |-- power
|   |   |   `-- state
|   |   |-- role
|   |   |-- roles
|   |   `-- speed
|   |-- 11.B2
|   |   |-- bitorder
|   |   |-- bus -> ../../../../../bus/visdn
|   |   |-- detach_state
|   |   |-- flags
|   |   |-- framing
|   |   |-- port_name
|   |   |-- power
|   |   |   `-- state
|   |   |-- role
|   |   |-- roles
|   |   `-- speed
|   |-- 11.D
|   |   |-- bitorder
|   |   |-- bus -> ../../../../../bus/visdn
|   |   |-- connected -> ../../../../../devices/visdn-system/netdev/8.1
|   |   |-- detach_state
|   |   |-- flags
|   |   |-- framing
|   |   |-- port_name
|   |   |-- power
|   |   |   `-- state
|   |   |-- role
|   |   |-- roles
|   |   `-- speed
|   |-- 11.E
|   |   |-- bitorder
|   |   |-- bus -> ../../../../../bus/visdn
|   |   |-- detach_state
|   |   |-- flags
|   |   |-- framing
|   |   |-- port_name
|   |   |-- power
|   |   |   `-- state
|   |   |-- role
|   |   |-- roles
|   |   `-- speed
|   |-- 11.SQ
|   |   |-- bitorder
|   |   |-- bus -> ../../../../../bus/visdn
|   |   |-- detach_state
|   |   |-- flags
|   |   |-- framing
|   |   |-- port_name
|   |   |-- power
|   |   |   `-- state
|   |   |-- role
|   |   |-- roles
|   |   `-- speed
|   |-- B1 -> ../../../../devices/pci0000:00/0000:00:09.0/11/11.B1
|   |-- B2 -> ../../../../devices/pci0000:00/0000:00:09.0/11/11.B2
|   |-- D -> ../../../../devices/pci0000:00/0000:00:09.0/11/11.D
|   |-- E -> ../../../../devices/pci0000:00/0000:00:09.0/11/11.E
|   |-- SQ -> ../../../../devices/pci0000:00/0000:00:09.0/11/11.SQ
|   |-- detach_state
|   |-- enabled
|   |-- l1_state
|   |-- port_id
|   |-- power
|   |   `-- state
|   |-- role
|   |-- st_clock_delay
|   `-- st_sampling_comp
|-- 12
|   |-- bitrate
|   |-- detach_state
|   |-- enabled
|   |-- master
|   |-- port_id
|   |-- power
|   |   `-- state
|   `-- slots_state
|-- bus -> ../../../bus/pci
|-- class
|-- config
|-- detach_state
|-- device
|-- driver -> ../../../bus/pci/drivers/hfc-pci
|-- fifo_state
|-- irq
|-- local_cpus
|-- pcm -> ../../../devices/pci0000:00/0000:00:09.0/12
|-- power
|   `-- state
|-- resource
|-- resource0
|-- resource1
|-- st0 -> ../../../devices/pci0000:00/0000:00:09.0/11
|-- subsystem_device
|-- subsystem_vendor
`-- vendor

You may see that the driver exports one S/T port whose unique ID is 11 and which is named st0. pcm0 (ID 12) is a PCM port facing towards an (unconfigured) hardware PCM bus.

Each port and each channel declare several attriutes. enabled for example, allows you to enable/disable the port which is normally disabled prior to configuration. l1_state may be used to read or modify the S/T port's L1 state.

Other attributes like fifo_state are device-wise and may be used to inspect internal card parameters.

A complete description of all the attributes exported by every driver may be found in the driver's page linked at the top of this page.