$Id: README,v 1.20 2004/03/08 17:29:32 samleffler Exp $


WARNING: THIS IS A BETA DISTRIBUTION.  THIS SOFTWARE HAS KNOWN PROBLEMS AND
WARNING: LIMITATIONS THAT WILL BE CORRECTED BEFORE A PRODUCTION RELEASE.
WARNING: DON'T BLAME US IF THE SOFTWARE EATS YOUR SYSTEM, DESTORYS YOUR DISK
WARNING: OR MAKES YOUR CORN-FLAKES SOGGY.
WARNING: USE AT YOUR OWN RISK!


MADWIFI: Multimode Atheros Driver for WiFi on Linux
===================================================

* Copyright (c) 2002-2004 Sam Leffler.  All rights reserved.

Read the file COPYRIGHT for the complete copyright.

This software contains a Linux kernel driver for Atheros-based
Wireless LAN devices.  The driver supports both station and AP modes
of operation.  The driver is actually a port of the BSD Atheros
driver and includes a port of the 802.11 link layer code originally
found in NetBSD.  You may/will also find other BSD-ish glue code.
As much as possible I've tried to make this driver a "native Linux"
driver that conforms to Linux style and operation but in some areas
of operation you will see elements of BSD design/operation.

The driver functions as a normal network device and uses the Wireless
Extensions API.  As such normal Linux tools can and should be used
with it.  

There is only one driver included here; it supports miniPCI and Cardbus
devices.  The driver can be built as a module or linked into the kernel.

The driver depends on two other modules: wlan.o and ath_hal.o.

The wlan module contains the 802.11 state machine, protocol support,
and other glue code.  This code is derived from work that first appeared
in NetBSD and then FreeBSD.

The ath_hal module contains the Atheros Hardware Access Layer (HAL).
This code manages much of the chip-specific operation of the driver.
The HAL is provided in a binary-only form in order to comply with
local regulatory agency requirements.  In the United States the FCC
mandates a radio transmitter can only be operated at power levels
and on frequency channels for which it is approved.  The FCC requires
that a software-defined radio cannot be configured by a user to
operate outside the approved power levels and frequency channels.
This makes it difficult to open-source code that enforces limits
on the power levels, frequency channels and other parameters of the
radio transmitter.  See

http://ftp.fcc.gov/Bureaus/Engineering_Technology/Orders/2001/fcc01264.pdf

for the specific FCC regulation.  Regulations for other agencies
are similar (often more stringent).  Because the module is provided
in a binary-only form it is marked "Proprietary"; this means when
you load it you will see messages that your system is now "tainted".

If you wish to use this driver on a platform for which an ath_hal
module is not already provided please contact the author.  Note that
this is only necessary for new _architectures_; the HAL is not tied to
any specific version of Linux.


Compatibility
=============
Testing has been done with kernel versions 2.4.20 and later, and
with wireless tools version 25 and later.  You may encounter some
rough edges when working with recent Linux kernels in the 2.6 branch
(or whatever the current development branch is the day you read this).

Atheros Hardware
================
There are currently 3 generations of Atheros 802.11 wireless devices:

5210	supports 11a only
5211	supports both 11a and 11b
5212	supports 11a, 11b, and 11g

These parts have been incorporated in a variety of retail products
including cardbus cards from DLink, Linksys, Netgear, Orinoco,
Proxim, and 3Com; and mini-pci cards from some of these same vendors.
In addition many laptop vendors use Atheros mini-pci cards for their
builtin wireless support.  For an up-to-date list of cards based
on Atheros parts visit:

http://customerproducts.atheros.com/customerproducts

In general, if a device is identified as ``11a only'' it is almost
certain to contain an Atheros 5210 part in it.  All retail a+b
products use the 5211.  The latest generation of universal a+b+g
combo products use the 5212.  When in doubt check the PCI vendor
id with a tool like lspci, the Atheros vendor id is 0x168c; e.g.

   00:13.0 Ethernet controller: Unknown device 168c:0012 (rev 01)

but beware that come vendors use alternate vendor id's (e.g 3Com).
The file hal/ah_devid.h has a list of known PCI id's.


Building the driver
===================
Most people can just type:

trouble% make

at the top level to build all the modules for the system where you
are building.  If this does not work or if you want to cross-compile
the code for a different system then you will need to do more setup.

Note that 2.4 kernel sources tree must have been populated with a
"make dep" for things to work correctly (if you use a tree where
you built the currently running kernel then all should be fine.)
For 2.6 kernels this step is not necessary.

To build the software four things are needed:

1. The target platform (e.g. i386-elf)
2. The location of the kernel include files.
3. The location of the kernel configuration file.
4. The location of the build tools.

The target platform is specified using; e.g.

trouble% export TARGET=i386-elf

The supported target platforms can be found with:

trouble% ls hal/linux/*.inc
hal/linux/Makefile.inc          hal/linux/mipsisa32-le-elf.inc
hal/linux/arm9-le-thumb-elf.inc hal/linux/powerpc-be-eabi.inc
hal/linux/i386-elf.inc          hal/linux/powerpc-le-eabi.inc
hal/linux/mipsisa32-be-elf.inc  hal/linux/xscale-be-elf.inc

A target specifies the CPU architecture, byte order, and the ABI/file
format.

The location of the kernel include files is typically given by
specifying the version of the kernel and then using default settings
for pathnames; e.g.

trouble% export KERNELRELEASE=2.4.20-8

This is sufficient if you have multiple kernel versions on your build
machine and you want to cross-build for a different version than your
are running.  However if the default locations are incorrect then you
will also need to override them; e.g.

trouble% export KERNELPATH=/cdrom/linuxppc-2.4.21-pre2-cerf/

(These settings are most often used when cross-compiling.)  

Finally, if you are cross-compiling you will probably need to
override the default toolchain settings that come with the software.
These settings are in files in the directory hal/linux/ that are
named <platform>.inc.  For example, the file for xscale-be-elf is:

#
# Compilation configuration for building big-endian XScale/arm-elf.
#

#
# Built with GNU cross-devel tools:
#
# PREFIX=/pub/gnu
# BINUTILS=binutils-2.14
# GCC=gcc-3.3.2
# target=arm-elf
#
# ${BINUTILS}/configure --target=$target --prefix=${PREFIX}
# ${GCC}/configure --target=$target   --prefix=${PREFIX} \
#	--enable-languages=c   --with-gnu-as --with-gnu-ld \
#	--with-newlib   --with-gxx-include-dir=${PREFIX}/$target/include
#
ifndef TOOLPREFIX
TOOLPREFIX=	/pub/gnu/bin/arm-elf-
endif
#
CC=	${TOOLPREFIX}gcc
LD=	${TOOLPREFIX}ld
STRIP=	${TOOLPREFIX}strip
OBJCOPY=${TOOLPREFIX}objcopy
NM=	${TOOLPREFIX}nm

LDOPTS=	-EB
COPTS+=	-DAH_BYTE_ORDER=AH_BIG_ENDIAN
COPTS+= -march=armv4 -mbig-endian -fno-strict-aliasing -fno-common -mapcs-32 \
	-mtune=xscale  -mshort-load-bytes -msoft-float

The first set of definitions specify the location and name of the
programs used to build the software.  The rest of the file defines
the compilation options for the target platform.  The latter should
usually not be changed because they were the options used to build
the binary HAL module, but TOOLPREFIX is unlikely to be right for
your system and you will want to change it; e.g

trouble% export TOOLPREFIX=/usr/local/bin/arm-elf-

to use programs installed in /usr/local/bin.  Note that mixing different
versions of the GNU tools may not work.  The .inc file for each target
platform specifies the exact toolchains used, including where they
were obtained (if pre-built).

The build system is designed to support cross-building without any
modification to the distribution files.  If you cannot do what you
need by setting environment variables please send patches to show
where things failed to do the right thing.


Once you have stuff configured appropriately, do:

    make

This will generate three important files:

Linux 2.6
    driver/ath_pci.ko (driver for PCI/Cardbus devices),
    ath_hal/ath_hal.ko (Atheros HAL), and
    wlan/wlan.ko (802.11 support layer)

Linux 2.4
    driver/ath_pci.o (driver for PCI/Cardbus devices),
    ath_hal/ath_hal.o (Atheros HAL), and
    wlan/wlan.o (802.11 support layer)

These files can be loaded with insmod or modprobe; e.g.

Linux 2.6
    insmod wlan/wlan.ko
    insmod ath_hal/ath_hal.ko
    insmod driver/ath_pci.ko

Linux 2.4
    insmod wlan/wlan.o
    insmod ath_hal/ath_hal.o
    insmod driver/ath_pci.o

(note you must load the wlan and ath_hal modules first as the driver
depends on them).  You can also try:

    make install

to install the drivers where they can be loaded automatically, i.e.
/lib/modules/<your kernel name>/net.


Note that you MUST do a "make clean" before compiling for a different
version of Linux; e.g. building for 2.6 after building for 2.4.

Using the driver
================
The driver should support any Atheros-based cardbus or pci device.
Management is done using the normal Linux tools such as ifconfig.
Support is included for versions 12 and later of the Wireless
Extensions so tools like iwconfig should work too.

To use this software in ``station mode'' (i.e. as a client) just
bring the interface up and the driver will scan for all access
points in all supported frequency bands supported by the hardware.
Specifically for 5210-based devices scanning will happen in the
5Ghz (11a) range, for 5211-based devices scanning will happen over
both 2Ghz (11b) and 5GHz frequencies (11a).  For 5212-based devices
the driver will scan both 2Ghz and 5GHz ranges and also look for
11g devices in the 2Ghz range.  To restrict operation you can either
select a mode (e.g. 11b) using iwpriv or, more commonly, select the
AP based on SSID and/or channel.

NOTE: You must mark the interface ``up'' with, e.g. ifconfig ath0 up
      before scanning for access points with iwlist.

To use this software in ``hostap mode'' you need to configure it
with iwconfig and you will probably want to lock the operating mode
to one of 11a, 11b, or 11g if you have a multi-mode card (if you
do not lock the mode then the driver will select a mode for you;
usually 11a).  In addition you will need to configure the system to
bridge frames to a wired LAN or similar.

NOTE: adhoc mode is known to not work reliably.

Wireless tools cribsheet:

iwlist ath0 scan		list AP's the driver has scanned
iwconfig ath0 essid "foo"	set the ssid to foo
iwpriv ath0 mode 1		lock operation to 11a only
iwpriv ath0 mode 2		lock operation to 11b only
iwpriv ath0 mode 3		lock operation to 11g only
iwpriv ath0 mode 0		autoselect from 11a/b/g (default)

There are some debugging mechanisms for the curious/masochistic:

sysctl -w dev.ath.debug=1	enable console msgs from the driver
sysctl -w dev.ath.dump="hal"	dump h/w register state to the console
echo 1>/proc/net/wlan0/debug	enable console msgs from the wlan module

In addition the program tools/athstats can be very useful in understanding
what is going on.  In particular, something like:

trouble% athstats 1

will give a running display of the most interesting statistics sampled
every 1 second.  Running athstats without any options will display a
summary of all non-zero statistics from the time the driver was loaded.
By default the ath0 device is used; to override this use the -i option.


Security/Crpto Support
======================
The driver supports fixed/shared key WEP using the hardware.  Newer
Atheros hardware is capable of much more (e.g. AES, TKIP and Michael)
but that work is not yet supported by the driver.

802.1x authenticator support and full WPA support (client and AP) is
planned.


Known Problems
==============
[All these problems are to be fixed in future revisions.]

0. The driver uses the BSD queue.h macros for managing various data
   structures.  It has been pointed out that this may conflict with the
   equivalent Linux definitions in list.h potentially causing problems
   in future versions of Linux.  The use of BSD macros will be removed
   in a future revision. [TEMPORARY WORKAROUND IN PLACE]

1. Adhoc mode is broken; symptoms are intermittent operation.
2. Performance in lossy environments is suboptimal.  The algorithm used to
   select the rate for transmitted packets is very simplistic.  There is no
   software retransmit; only hardware retransmit is used.  Contributors are
   encouraged to replace the existing rate control algorithm with a better
   one (hint: all the information needed is available in the driver).
3. 11g AP support is incomplete. We don't set the slot time in the driver
   and do not turn off short slot time when an 11b station joins the ntework.
4. The driver does not fully enable power-save operation of the chip;
   consequently power use is suboptimal.

Acknowledgements
================
This work could not have been done without the support of Atheros
and in particular the efforts of Greg Chesson.  Comments from David
Miller were helpful in cleaning up some of the roughest edges in
early versions of the driver.

Many people have contributed fixes and improvements to this software
including:

Joerg Albert
Tong Chia
William S. Kish
Mathieu Lacage
Stephane Laroche
Tom Marshall
Nick Moss
Nick Petroni
Henry Qian
Carl Thompson
giova+mwfdev@faglioni.it
D. Stolte

(Apologies to anyone whose name was unintentionally left off.)

Feedback and Contributions
==========================
This project is hosted at http://madwifi.sourceforge.net.  Fixes and
enhancements are encouraged.  Please send all bug reports about this
driver to:

	madwifi-users@lists.sourceforge.net

When sending a problem report be sure to include the version of the
driver and the part identification the driver prints to the console when
the module is loaded.  For example,

ath_hal: 0.8.2.0
wlan: 0.7.0.0
ath_pci: 0.8.2.0
PCI: Found IRQ 11 for device 00:13.0
ath0: 11a rates: 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
ath0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
ath0: 802.11 address: 00:05:5d:6f:99:5f
ath0: Atheros 5211: mem=0xfebf0000, irq=11

This says the HAL module is version 0.8.2, the wlan module is version
0.7, the driver is version 0.8.2 and the hardware uses an Atheros
5211 chip (which supports 11a and 11b modes).

We will try to respond in a timely manner but understand this software
is provided as-is; i.e. with no promise of support.
