The
awi driver supports various IEEE 802.11 wireless cards that run AMD PCnetMobile firmware based on the AMD 79c930 controller with the Intersil (formerly Harris) PRISM radio chipset. It provides access to 32kb of memory shared between the controller and the host. All host/device interaction is accomplished via this shared memory, which can be accessed either via PCMCIA or I/O memory spaces. The
awi driver encapsulates all IP and ARP traffic in 802.11 frames.
The driver works both in infrastructure mode and in ad-hoc (independent BSS) mode.
In infrastructure mode, it communicates with an Access Point, which serves as a link-layer bridge between an Ethernet segment and the wireless network. An access point also provides roaming capability, which allows a wireless node to move between access points.
In ad-hoc mode, the device communicates peer to peer. Although it is more efficient to communicate between wireless nodes, the coverage is limited spatially due to the lack of roaming capability.
In addition to these two modes in the IEEE 802.11 specification, the
awi driver also supports a variant of ad-hoc mode outside of the spec for DS radio cards. This makes it possible to communicate with the WaveLAN ad-hoc mode of
wi(4) driver. The NWID has no effect in this mode.
Another mode added to the
awi driver can be used with old Melco access points with 2Mbps cards. This mode actually uses the IEEE 802.11 ad-hoc mode with encapsulation of raw Ethernet packets (including headers) in 802.11 frames.
For more information on configuring this device, see
ifconfig(8) and
ifmedia(4).