Contents of /alx-src/trunk/kernel26-alx/linux/Documentation/arm/README

			   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 2.95.1, EGCS
  1.1.2, and GCC 3.3 are known to be good compilers.  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/patches/info.html  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/forms/solution.shtml

  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-$(MACHINE) directories which are
  designed to house the non-driver files for a particular machine (eg, PCI,
  memory management, architecture definitions etc).  For all future
  machines, there should be a corresponding include/asm-arm/arch-$(MACHINE)
  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, 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
  include/asm-arm/arch-<class> - which contain the source files to
  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."

  This fine-grained machine specific 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/>

---
Russell King (15/03/2004)
1	ARM Linux 2.6
2	=============
3
4	Please check <ftp://ftp.arm.linux.org.uk/pub/armlinux> for
5	updates.
6
7	Compilation of kernel
8	---------------------
9
10	In order to compile ARM Linux, you will need a compiler capable of
11	generating ARM ELF code with GNU extensions. GCC 2.95.1, EGCS
12	1.1.2, and GCC 3.3 are known to be good compilers. Fortunately, you
13	needn't guess. The kernel will report an error if your compiler is
14	a recognized offender.
15
16	To build ARM Linux natively, you shouldn't have to alter the ARCH = line
17	in the top level Makefile. However, if you don't have the ARM Linux ELF
18	tools installed as default, then you should change the CROSS_COMPILE
19	line as detailed below.
20
21	If you wish to cross-compile, then alter the following lines in the top
22	level make file:
23
24	ARCH = <whatever>
25	with
26	ARCH = arm
27
28	and
29
30	CROSS_COMPILE=
31	to
32	CROSS_COMPILE=<your-path-to-your-compiler-without-gcc>
33	eg.
34	CROSS_COMPILE=arm-linux-
35
36	Do a 'make config', followed by 'make Image' to build the kernel
37	(arch/arm/boot/Image). A compressed image can be built by doing a
38	'make zImage' instead of 'make Image'.
39
40
41	Bug reports etc
42	---------------
43
44	Please send patches to the patch system. For more information, see
45	http://www.arm.linux.org.uk/patches/info.html Always include some
46	explanation as to what the patch does and why it is needed.
47
48	Bug reports should be sent to linux-arm-kernel@lists.arm.linux.org.uk,
49	or submitted through the web form at
50	http://www.arm.linux.org.uk/forms/solution.shtml
51
52	When sending bug reports, please ensure that they contain all relevant
53	information, eg. the kernel messages that were printed before/during
54	the problem, what you were doing, etc.
55
56
57	Include files
58	-------------
59
60	Several new include directories have been created under include/asm-arm,
61	which are there to reduce the clutter in the top-level directory. These
62	directories, and their purpose is listed below:
63
64	arch-* machine/platform specific header files
65	hardware driver-internal ARM specific data structures/definitions
66	mach descriptions of generic ARM to specific machine interfaces
67	proc-* processor dependent header files (currently only two
68	categories)
69
70
71	Machine/Platform support
72	------------------------
73
74	The ARM tree contains support for a lot of different machine types. To
75	continue supporting these differences, it has become necessary to split
76	machine-specific parts by directory. For this, the machine category is
77	used to select which directories and files get included (we will use
78	$(MACHINE) to refer to the category)
79
80	To this end, we now have arch/arm/mach-$(MACHINE) directories which are
81	designed to house the non-driver files for a particular machine (eg, PCI,
82	memory management, architecture definitions etc). For all future
83	machines, there should be a corresponding include/asm-arm/arch-$(MACHINE)
84	directory.
85
86
87	Modules
88	-------
89
90	Although modularisation is supported (and required for the FP emulator),
91	each module on an ARM2/ARM250/ARM3 machine when is loaded will take
92	memory up to the next 32k boundary due to the size of the pages.
93	Therefore, modularisation on these machines really worth it?
94
95	However, ARM6 and up machines allow modules to take multiples of 4k, and
96	as such Acorn RiscPCs and other architectures using these processors can
97	make good use of modularisation.
98
99
100	ADFS Image files
101	----------------
102
103	You can access image files on your ADFS partitions by mounting the ADFS
104	partition, and then using the loopback device driver. You must have
105	losetup installed.
106
107	Please note that the PCEmulator DOS partitions have a partition table at
108	the start, and as such, you will have to give '-o offset' to losetup.
109
110
111	Request to developers
112	---------------------
113
114	When writing device drivers which include a separate assembler file, please
115	include it in with the C file, and not the arch/arm/lib directory. This
116	allows the driver to be compiled as a loadable module without requiring
117	half the code to be compiled into the kernel image.
118
119	In general, try to avoid using assembler unless it is really necessary. It
120	makes drivers far less easy to port to other hardware.
121
122
123	ST506 hard drives
124	-----------------
125
126	The ST506 hard drive controllers seem to be working fine (if a little
127	slowly). At the moment they will only work off the controllers on an
128	A4x0's motherboard, but for it to work off a Podule just requires
129	someone with a podule to add the addresses for the IRQ mask and the
130	HDC base to the source.
131
132	As of 31/3/96 it works with two drives (you should get the ADFS
133	*configure harddrive set to 2). I've got an internal 20MB and a great
134	big external 5.25" FH 64MB drive (who could ever want more :-) ).
135
136	I've just got 240K/s off it (a dd with bs=128k); thats about half of what
137	RiscOS gets; but it's a heck of a lot better than the 50K/s I was getting
138	last week :-)
139
140	Known bug: Drive data errors can cause a hang; including cases where
141	the controller has fixed the error using ECC. (Possibly ONLY
142	in that case...hmm).
143
144
145	1772 Floppy
146	-----------
147	This also seems to work OK, but hasn't been stressed much lately. It
148	hasn't got any code for disc change detection in there at the moment which
149	could be a bit of a problem! Suggestions on the correct way to do this
150	are welcome.
151
152
153	CONFIG_MACH_ and CONFIG_ARCH_
154	-----------------------------
155	A change was made in 2003 to the macro names for new machines.
156	Historically, CONFIG_ARCH_ was used for the bonafide architecture,
157	e.g. SA1100, as well as implementations of the architecture,
158	e.g. Assabet. It was decided to change the implementation macros
159	to read CONFIG_MACH_ for clarity. Moreover, a retroactive fixup has
160	not been made because it would complicate patching.
161
162	Previous registrations may be found online.
163
164	<http://www.arm.linux.org.uk/developer/machines/>
165
166	Kernel entry (head.S)
167	--------------------------
168	The initial entry into the kernel is via head.S, which uses machine
169	independent code. The machine is selected by the value of 'r1' on
170	entry, which must be kept unique.
171
172	Due to the large number of machines which the ARM port of Linux provides
173	for, we have a method to manage this which ensures that we don't end up
174	duplicating large amounts of code.
175
176	We group machine (or platform) support code into machine classes. A
177	class typically based around one or more system on a chip devices, and
178	acts as a natural container around the actual implementations. These
179	classes are given directories - arch/arm/mach-<class> and
180	include/asm-arm/arch-<class> - which contain the source files to
181	support the machine class. This directories also contain any machine
182	specific supporting code.
183
184	For example, the SA1100 class is based upon the SA1100 and SA1110 SoC
185	devices, and contains the code to support the way the on-board and off-
186	board devices are used, or the device is setup, and provides that
187	machine specific "personality."
188
189	This fine-grained machine specific selection is controlled by the machine
190	type ID, which acts both as a run-time and a compile-time code selection
191	method.
192
193	You can register a new machine via the web site at:
194
195	<http://www.arm.linux.org.uk/developer/machines/>
196
197	---
198	Russell King (15/03/2004)