To determine the mode,
el_autosense_thread( )
tries to send a test data
packet in each of the possible modes. When it successfully transmits the data
packet, it sets the network interface to that mode. The
lm_media_mode
,
lm_media
, and
lm_media_state
members of the
el_softc
data structure
keep track of the progress of the autosensing procedure, as follows:
•
The value of the
lm_media_mode
member determines whether the
el_autosense_thread( )
will automatically determine the network
interface, or whether the user specified the type of media.
•
The
lm_media
member specifies the current media. This member
changes each time that the driver uses a different medium to try to
transmit a packet. The
if_el
device driver can set this member to any
of the following values:
LAN_MEDIA_UTP
The media is unshielded twisted-pair cable.
LAN_MEDIA_BNC
The media is thin wire.
LAN_MEDIA_AUI
The media is the attachment unit
interface (AUI).
•
The
lm_media_state
member specifies the current state of the
autosensing procedure, as follows:
LAN_MEDIA_STATE_SENSING
The driver is trying to determine
the media mode.
LAN_MEDIA_STATE_DETERMINED
The media state has been determined.
The
el_autosense_thread( )
routine is implemented as a kernel thread.
It performs the following tasks:
•
Blocks until awakened (Section 5.3.2)
•
Tests for the termination flag (Section 5.3.3)
•
Starts up statistics (Section 5.3.4)
•
Enters the packet transmit loop (Section 5.3.5)
•
Saves counters prior to the transmit operation (Section 5.3.6)
•
Allocates memory for a test packet (Section 5.3.7)
•
Uses the default from the ROM (Section 5.3.8)
•
Sets the media setting in the hardware (Section 5.3.9)
•
Builds a test packet to transmit (Section 5.3.10)
•
Transmits the test packet (Section 5.3.11)
•
Sets a timer for the current kernel thread (Section 5.3.12)
•
Tests for loss of carrier (Section 5.3.13)
5–18 Implementing the Autoconfiguration Support Section (probe)
