dmc(4)
NAME
dmc − DMC11/DMR11 communications interface
SYNTAX
device dmc0 at uba0 csr 0167600 flags 0x???? vector dmcrint dmcxint
DESCRIPTION
The dmc interface provides access to a point-to-point communications device that runs at either 1 Mb/s or 56 Kb/s. DMC11s communicate using the DDCMP link layer protocol.
The dmc interface driver also supports a DMR11 providing point-to-point communication running at data rates from 2.4 Kb/s to 1 Mb/s. DMR11s are a more recent design and thus are preferred over DMC11s.
The host address must be specified with an SIOCSIFADDR ioctl before the interface will transmit or receive any packets.
Several protocols can be multiplexed over a dmc link simultaneously. Conversely, a dmc can be set up such that only one protocol family can use that device. If the latter approach is taken, an SIOCSTATE ioctl must be issued by the protocol family requesting device ownership. The family address must appear in the “if_family” structure member, and “if_nomuxhdr” must be set. Before requesting ownership, the device’s current ownership should be read and saved. This will allow device ownership to be returned to a previous owner.
The first byte of the flags word can be set up to indicate what mode the device should use. The supported modes are 0 for full duplex, 1 for maintenance mode, and 2 for half duplex. In addition, if the device is a dmr, the number of outstanding transmit buffers can be increased from a default of 7 to a maximum of 24 buffers by specifying a hexadecimal value in the second byte of the flags word. For example, if the flags word is set to 0x1800, then 24 transmit buffers will be allocated on a device set up to run full duplex.
DIAGNOSTICS
dmcprobe: can’t start device. The dmc could not be started at boot time.
dmcinit: DMC not running. The dmc unexpectedly stopped running.
dmc%d: done unalloc rbuf. The dmc returned a receive or transmit buffer that was not allocated to it.
dmc%d: bad control %o. A bad parameter was passed to the dmcload routine.
dmc%d: unknown address type %d. An input packet was received that contained a type of address unknown to the driver.
dmc%d: bad packet address 0x%x. The device returned a buffer with an unexpected buffer address.
dmc%d: can’t handle af%d. The interface was handed a message that has addresses formatted in an unsuitable address family. Formerly reported as dmc%d: af%d not supported.
dmc%d: internal loopback enable requested. The device is being put in internal loopback at a user’s request.
dmc%d: internal loopback disable requested. The device is being taken out of internal loopback at a user’s request.
DMC FATAL ERROR 0%o.
DMC SOFT ERROR 0%o.