90 lines
4.1 KiB
Plaintext
90 lines
4.1 KiB
Plaintext
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BCM43xx Linux Driver Project
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============================
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Introduction
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------------
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Many of the wireless devices found in modern notebook computers are
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based on the wireless chips produced by Broadcom. These devices have
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been a problem for Linux users as there is no open-source driver
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available. In addition, Broadcom has not released specifications
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for the device, and driver availability has been limited to the
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binary-only form used in the GPL versions of AP hardware such as the
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Linksys WRT54G, and the Windows and OS X drivers. Before this project
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began, the only way to use these devices were to use the Windows or
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OS X drivers with either the Linuxant or ndiswrapper modules. There
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is a strong penalty if this method is used as loading the binary-only
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module "taints" the kernel, and no kernel developer will help diagnose
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any kernel problems.
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Development
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-----------
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This driver has been developed using
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a clean-room technique that is described at
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http://bcm-specs.sipsolutions.net/ReverseEngineeringProcess. For legal
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reasons, none of the clean-room crew works on the on the Linux driver,
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and none of the Linux developers sees anything but the specifications,
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which are the ultimate product of the reverse-engineering group.
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Software
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--------
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Since the release of the 2.6.17 kernel, the bcm43xx driver has been
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distributed with the kernel source, and is prebuilt in most, if not
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all, distributions. There is, however, additional software that is
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required. The firmware used by the chip is the intellectual property
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of Broadcom and they have not given the bcm43xx team redistribution
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rights to this firmware. Since we cannot legally redistribute
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the firwmare we cannot include it with the driver. Furthermore, it
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cannot be placed in the downloadable archives of any distributing
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organization; therefore, the user is responsible for obtaining the
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firmware and placing it in the appropriate location so that the driver
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can find it when initializing.
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To help with this process, the bcm43xx developers provide a separate
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program named bcm43xx-fwcutter to "cut" the firmware out of a
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Windows or OS X driver and write the extracted files to the proper
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location. This program is usually provided with the distribution;
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however, it may be downloaded from
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http://developer.berlios.de/project/showfiles.php?group_id=4547
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The firmware is available in two versions. V3 firmware is used with
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the in-kernel bcm43xx driver that uses a software MAC layer called
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SoftMAC, and will have a microcode revision of 0x127 or smaller. The
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V4 firmware is used by an out-of-kernel driver employing a variation of
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the Devicescape MAC layer known as d80211. Once bcm43xx-d80211 reaches
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a satisfactory level of development, it will replace bcm43xx-softmac
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in the kernel as it is much more flexible and powerful.
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A source for the latest V3 firmware is
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http://downloads.openwrt.org/sources/wl_apsta-3.130.20.0.o
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Once this file is downloaded, the command
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'bcm43xx-fwcutter -w <dir> <filename>'
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will extract the microcode and write it to directory
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<dir>. The correct directory will depend on your distribution;
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however, most use '/lib/firmware'. Once this step is completed,
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the bcm3xx driver should load when the system is booted. To see
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any messages relating to the driver, issue the command 'dmesg |
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grep bcm43xx' from a terminal window. If there are any problems,
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please send that output to Bcm43xx-dev@lists.berlios.de.
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Although the driver has been in-kernel since 2.6.17, the earliest
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version is quite limited in its capability. Patches that include
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all features of later versions are available for the stable kernel
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versions from 2.6.18. These will be needed if you use a BCM4318,
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or a PCI Express version (BCM4311 and BCM4312). In addition, if you
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have an early BCM4306 and more than 1 GB RAM, your kernel will need
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to be patched. These patches, which are being updated regularly,
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are available at ftp://lwfinger.dynalias.org/patches. Look for
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combined_2.6.YY.patch. Of course you will need kernel source downloaded
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from kernel.org, or the source from your distribution.
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If you build your own kernel, please enable CONFIG_BCM43XX_DEBUG
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and CONFIG_IEEE80211_SOFTMAC_DEBUG. The log information provided is
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essential for solving any problems.
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