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- ARM Linux 2.6
- =============
-
- Please check <ftp://ftp.arm.linux.org.uk/pub/armlinux> for
- updates.
-
-Compilation of kernel
----------------------
-
- In order to compile ARM Linux, you will need a compiler capable of
- generating ARM ELF code with GNU extensions. GCC 3.3 is known to be
- a good compiler. Fortunately, you needn't guess. The kernel will report
- an error if your compiler is a recognized offender.
-
- To build ARM Linux natively, you shouldn't have to alter the ARCH = line
- in the top level Makefile. However, if you don't have the ARM Linux ELF
- tools installed as default, then you should change the CROSS_COMPILE
- line as detailed below.
-
- If you wish to cross-compile, then alter the following lines in the top
- level make file:
-
- ARCH = <whatever>
- with
- ARCH = arm
-
- and
-
- CROSS_COMPILE=
- to
- CROSS_COMPILE=<your-path-to-your-compiler-without-gcc>
- eg.
- CROSS_COMPILE=arm-linux-
-
- Do a 'make config', followed by 'make Image' to build the kernel
- (arch/arm/boot/Image). A compressed image can be built by doing a
- 'make zImage' instead of 'make Image'.
-
-
-Bug reports etc
----------------
-
- Please send patches to the patch system. For more information, see
- http://www.arm.linux.org.uk/developer/patches/info.php Always include some
- explanation as to what the patch does and why it is needed.
-
- Bug reports should be sent to linux-arm-kernel@lists.arm.linux.org.uk,
- or submitted through the web form at
- http://www.arm.linux.org.uk/developer/
-
- When sending bug reports, please ensure that they contain all relevant
- information, eg. the kernel messages that were printed before/during
- the problem, what you were doing, etc.
-
-
-Include files
--------------
-
- Several new include directories have been created under include/asm-arm,
- which are there to reduce the clutter in the top-level directory. These
- directories, and their purpose is listed below:
-
- arch-* machine/platform specific header files
- hardware driver-internal ARM specific data structures/definitions
- mach descriptions of generic ARM to specific machine interfaces
- proc-* processor dependent header files (currently only two
- categories)
-
-
-Machine/Platform support
-------------------------
-
- The ARM tree contains support for a lot of different machine types. To
- continue supporting these differences, it has become necessary to split
- machine-specific parts by directory. For this, the machine category is
- used to select which directories and files get included (we will use
- $(MACHINE) to refer to the category)
-
- To this end, we now have arch/arm/mach-$(MACHINE) directories which are
- designed to house the non-driver files for a particular machine (eg, PCI,
- memory management, architecture definitions etc). For all future
- machines, there should be a corresponding arch/arm/mach-$(MACHINE)/include/mach
- directory.
-
-
-Modules
--------
-
- Although modularisation is supported (and required for the FP emulator),
- each module on an ARM2/ARM250/ARM3 machine when is loaded will take
- memory up to the next 32k boundary due to the size of the pages.
- Therefore, is modularisation on these machines really worth it?
-
- However, ARM6 and up machines allow modules to take multiples of 4k, and
- as such Acorn RiscPCs and other architectures using these processors can
- make good use of modularisation.
-
-
-ADFS Image files
-----------------
-
- You can access image files on your ADFS partitions by mounting the ADFS
- partition, and then using the loopback device driver. You must have
- losetup installed.
-
- Please note that the PCEmulator DOS partitions have a partition table at
- the start, and as such, you will have to give '-o offset' to losetup.
-
-
-Request to developers
----------------------
-
- When writing device drivers which include a separate assembler file, please
- include it in with the C file, and not the arch/arm/lib directory. This
- allows the driver to be compiled as a loadable module without requiring
- half the code to be compiled into the kernel image.
-
- In general, try to avoid using assembler unless it is really necessary. It
- makes drivers far less easy to port to other hardware.
-
-
-ST506 hard drives
------------------
-
- The ST506 hard drive controllers seem to be working fine (if a little
- slowly). At the moment they will only work off the controllers on an
- A4x0's motherboard, but for it to work off a Podule just requires
- someone with a podule to add the addresses for the IRQ mask and the
- HDC base to the source.
-
- As of 31/3/96 it works with two drives (you should get the ADFS
- *configure harddrive set to 2). I've got an internal 20MB and a great
- big external 5.25" FH 64MB drive (who could ever want more :-) ).
-
- I've just got 240K/s off it (a dd with bs=128k); thats about half of what
- RiscOS gets; but it's a heck of a lot better than the 50K/s I was getting
- last week :-)
-
- Known bug: Drive data errors can cause a hang; including cases where
- the controller has fixed the error using ECC. (Possibly ONLY
- in that case...hmm).
-
-
-1772 Floppy
------------
- This also seems to work OK, but hasn't been stressed much lately. It
- hasn't got any code for disc change detection in there at the moment which
- could be a bit of a problem! Suggestions on the correct way to do this
- are welcome.
-
-
-CONFIG_MACH_ and CONFIG_ARCH_
------------------------------
- A change was made in 2003 to the macro names for new machines.
- Historically, CONFIG_ARCH_ was used for the bonafide architecture,
- e.g. SA1100, as well as implementations of the architecture,
- e.g. Assabet. It was decided to change the implementation macros
- to read CONFIG_MACH_ for clarity. Moreover, a retroactive fixup has
- not been made because it would complicate patching.
-
- Previous registrations may be found online.
-
- <http://www.arm.linux.org.uk/developer/machines/>
-
-Kernel entry (head.S)
---------------------------
- The initial entry into the kernel is via head.S, which uses machine
- independent code. The machine is selected by the value of 'r1' on
- entry, which must be kept unique.
-
- Due to the large number of machines which the ARM port of Linux provides
- for, we have a method to manage this which ensures that we don't end up
- duplicating large amounts of code.
-
- We group machine (or platform) support code into machine classes. A
- class typically based around one or more system on a chip devices, and
- acts as a natural container around the actual implementations. These
- classes are given directories - arch/arm/mach-<class> and
- arch/arm/mach-<class> - which contain the source files to/include/mach
- support the machine class. This directories also contain any machine
- specific supporting code.
-
- For example, the SA1100 class is based upon the SA1100 and SA1110 SoC
- devices, and contains the code to support the way the on-board and off-
- board devices are used, or the device is setup, and provides that
- machine specific "personality."
-
- For platforms that support device tree (DT), the machine selection is
- controlled at runtime by passing the device tree blob to the kernel. At
- compile-time, support for the machine type must be selected. This allows for
- a single multiplatform kernel build to be used for several machine types.
-
- For platforms that do not use device tree, this machine selection is
- controlled by the machine type ID, which acts both as a run-time and a
- compile-time code selection method. You can register a new machine via the
- web site at:
-
- <http://www.arm.linux.org.uk/developer/machines/>
-
- Note: Please do not register a machine type for DT-only platforms. If your
- platform is DT-only, you do not need a registered machine type.
-
----
-Russell King (15/03/2004)