About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / arm / README

Custom Search

Based on kernel version 4.13.3. Page generated on 2017-09-23 13:54 EST.

1				   ARM Linux 2.6
2				   =============
4	    Please check <ftp://ftp.arm.linux.org.uk/pub/armlinux> for
5	    updates.
7	Compilation of kernel
8	---------------------
10	  In order to compile ARM Linux, you will need a compiler capable of
11	  generating ARM ELF code with GNU extensions.  GCC 3.3 is known to be
12	  a good compiler.  Fortunately, you needn't guess.  The kernel will report
13	  an error if your compiler is a recognized offender.
15	  To build ARM Linux natively, you shouldn't have to alter the ARCH = line
16	  in the top level Makefile.  However, if you don't have the ARM Linux ELF
17	  tools installed as default, then you should change the CROSS_COMPILE
18	  line as detailed below.
20	  If you wish to cross-compile, then alter the following lines in the top
21	  level make file:
23	    ARCH = <whatever>
24		with
25	    ARCH = arm
27		and
30		to
31	    CROSS_COMPILE=<your-path-to-your-compiler-without-gcc>
32		eg.
33	    CROSS_COMPILE=arm-linux-
35	  Do a 'make config', followed by 'make Image' to build the kernel 
36	  (arch/arm/boot/Image).  A compressed image can be built by doing a 
37	  'make zImage' instead of 'make Image'.
40	Bug reports etc
41	---------------
43	  Please send patches to the patch system.  For more information, see
44	  http://www.arm.linux.org.uk/developer/patches/info.php Always include some
45	  explanation as to what the patch does and why it is needed.
47	  Bug reports should be sent to linux-arm-kernel@lists.arm.linux.org.uk,
48	  or submitted through the web form at
49	  http://www.arm.linux.org.uk/developer/ 
51	  When sending bug reports, please ensure that they contain all relevant
52	  information, eg. the kernel messages that were printed before/during
53	  the problem, what you were doing, etc.
56	Include files
57	-------------
59	  Several new include directories have been created under include/asm-arm,
60	  which are there to reduce the clutter in the top-level directory.  These
61	  directories, and their purpose is listed below:
63	   arch-*	machine/platform specific header files
64	   hardware	driver-internal ARM specific data structures/definitions
65	   mach		descriptions of generic ARM to specific machine interfaces
66	   proc-*	processor dependent header files (currently only two
67			categories)
70	Machine/Platform support
71	------------------------
73	  The ARM tree contains support for a lot of different machine types.  To
74	  continue supporting these differences, it has become necessary to split
75	  machine-specific parts by directory.  For this, the machine category is
76	  used to select which directories and files get included (we will use
77	  $(MACHINE) to refer to the category)
79	  To this end, we now have arch/arm/mach-$(MACHINE) directories which are
80	  designed to house the non-driver files for a particular machine (eg, PCI,
81	  memory management, architecture definitions etc).  For all future
82	  machines, there should be a corresponding arch/arm/mach-$(MACHINE)/include/mach
83	  directory.
86	Modules
87	-------
89	  Although modularisation is supported (and required for the FP emulator),
90	  each module on an ARM2/ARM250/ARM3 machine when is loaded will take
91	  memory up to the next 32k boundary due to the size of the pages.
92	  Therefore, is modularisation on these machines really worth it?
94	  However, ARM6 and up machines allow modules to take multiples of 4k, and
95	  as such Acorn RiscPCs and other architectures using these processors can
96	  make good use of modularisation.
99	ADFS Image files
100	----------------
102	  You can access image files on your ADFS partitions by mounting the ADFS
103	  partition, and then using the loopback device driver.  You must have
104	  losetup installed.
106	  Please note that the PCEmulator DOS partitions have a partition table at
107	  the start, and as such, you will have to give '-o offset' to losetup.
110	Request to developers
111	---------------------
113	  When writing device drivers which include a separate assembler file, please
114	  include it in with the C file, and not the arch/arm/lib directory.  This
115	  allows the driver to be compiled as a loadable module without requiring
116	  half the code to be compiled into the kernel image.
118	  In general, try to avoid using assembler unless it is really necessary.  It
119	  makes drivers far less easy to port to other hardware.
122	ST506 hard drives
123	-----------------
125	  The ST506 hard drive controllers seem to be working fine (if a little
126	  slowly).  At the moment they will only work off the controllers on an
127	  A4x0's motherboard, but for it to work off a Podule just requires
128	  someone with a podule to add the addresses for the IRQ mask and the
129	  HDC base to the source.
131	  As of 31/3/96 it works with two drives (you should get the ADFS
132	  *configure harddrive set to 2). I've got an internal 20MB and a great
133	  big external 5.25" FH 64MB drive (who could ever want more :-) ).
135	  I've just got 240K/s off it (a dd with bs=128k); thats about half of what
136	  RiscOS gets; but it's a heck of a lot better than the 50K/s I was getting
137	  last week :-)
139	  Known bug: Drive data errors can cause a hang; including cases where
140	  the controller has fixed the error using ECC. (Possibly ONLY
141	  in that case...hmm).
144	1772 Floppy
145	-----------
146	  This also seems to work OK, but hasn't been stressed much lately.  It
147	  hasn't got any code for disc change detection in there at the moment which
148	  could be a bit of a problem!  Suggestions on the correct way to do this
149	  are welcome.
153	-----------------------------
154	  A change was made in 2003 to the macro names for new machines.
155	  Historically, CONFIG_ARCH_ was used for the bonafide architecture,
156	  e.g. SA1100, as well as implementations of the architecture,
157	  e.g. Assabet.  It was decided to change the implementation macros
158	  to read CONFIG_MACH_ for clarity.  Moreover, a retroactive fixup has
159	  not been made because it would complicate patching.
161	  Previous registrations may be found online.
163	    <http://www.arm.linux.org.uk/developer/machines/>
165	Kernel entry (head.S)
166	--------------------------
167	  The initial entry into the kernel is via head.S, which uses machine
168	  independent code.  The machine is selected by the value of 'r1' on
169	  entry, which must be kept unique.
171	  Due to the large number of machines which the ARM port of Linux provides
172	  for, we have a method to manage this which ensures that we don't end up
173	  duplicating large amounts of code.
175	  We group machine (or platform) support code into machine classes.  A
176	  class typically based around one or more system on a chip devices, and
177	  acts as a natural container around the actual implementations.  These
178	  classes are given directories - arch/arm/mach-<class> and
179	  arch/arm/mach-<class> - which contain the source files to/include/mach
180	  support the machine class.  This directories also contain any machine
181	  specific supporting code.
183	  For example, the SA1100 class is based upon the SA1100 and SA1110 SoC
184	  devices, and contains the code to support the way the on-board and off-
185	  board devices are used, or the device is setup, and provides that
186	  machine specific "personality."
188	  For platforms that support device tree (DT), the machine selection is
189	  controlled at runtime by passing the device tree blob to the kernel.  At
190	  compile-time, support for the machine type must be selected.  This allows for
191	  a single multiplatform kernel build to be used for several machine types.
193	  For platforms that do not use device tree, this machine selection is
194	  controlled by the machine type ID, which acts both as a run-time and a
195	  compile-time code selection method.  You can register a new machine via the
196	  web site at:
198	    <http://www.arm.linux.org.uk/developer/machines/>
200	  Note: Please do not register a machine type for DT-only platforms.  If your
201	  platform is DT-only, you do not need a registered machine type.
203	---
204	Russell King (15/03/2004)
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.