README
1 ARM Linux 2.4
2 =============
3
4 Please check ftp.arm.linux.org.uk:/pub/armlinux for latest updates.
5
6Compilation of kernel
7---------------------
8
9 In order to compile ARM Linux, you will need a compiler capable of
10 generating ARM ELF code with GNU extensions. GCC 2.95.1 and EGCS 1.1.2
11 are good compilers.
12
13 To build ARM Linux natively, you shouldn't have to alter the ARCH = line
14 in the top level Makefile. However, if you don't have the ARM Linux ELF
15 tools installed as default, then you should change the CROSS_COMPILE
16 line as detailed below.
17
18 If you wish to cross-compile, then alter the following lines in the top
19 level make file:
20
21 ARCH = <whatever>
22 with
23 ARCH = arm
24
25 and
26
27 CROSS_COMPILE=
28 to
29 CROSS_COMPILE=<your-path-to-your-compiler-without-gcc>
30 eg.
31 CROSS_COMPILE=arm-linux-
32
33 Do a 'make config', followed by 'make dep', and finally 'make Image' to
34 build the kernel (arch/arm/boot/Image). A compressed image can be built
35 by doing a 'make zImage' instead of 'make Image'.
36
37
38Bug reports etc
39---------------
40
41 Please send patches to the patch system. For more information, see
42 http://www.arm.linux.org.uk/patches/info.html Always include some
43 explanation as to what the patch does and why it is needed.
44
45 Bug reports should be sent to linux-arm-kernel@lists.arm.linux.org.uk,
46 or submitted through the web form at
47 http://www.arm.linux.org.uk/forms/solution.shtml
48
49 When sending bug reports, please ensure that they contain all relevant
50 information, eg. the kernel messages that were printed before/during
51 the problem, what you were doing, etc.
52
53
54Include files
55-------------
56
57 Several new include directories have been created under include/asm-arm,
58 which are there to reduce the clutter in the top-level directory. These
59 directories, and their purpose is listed below:
60
61 arch-* machine/platform specific header files
62 hardware driver-internal ARM specific data structures/definitions
63 mach descriptions of generic ARM to specific machine interfaces
64 proc-* processor dependent header files (currently only two
65 categories)
66
67
68Machine/Platform support
69------------------------
70
71 The ARM tree contains support for a lot of different machine types. To
72 continue supporting these differences, it has become necessary to split
73 machine-specific parts by directory. For this, the machine category is
74 used to select which directories and files get included (we will use
75 $(MACHINE) to refer to the category)
76
77 To this end, we now have arch/arm/mach-$(MACHINE) directories which are
78 designed to house the non-driver files for a particular machine (eg, PCI,
79 memory management, architecture definitions etc). For all future
80 machines, there should be a corresponding include/asm-arm/arch-$(MACHINE)
81 directory.
82
83
84Modules
85-------
86
87 Although modularisation is supported (and required for the FP emulator),
88 each module on an ARM2/ARM250/ARM3 machine when is loaded will take
89 memory up to the next 32k boundary due to the size of the pages.
90 Therefore, modularisation on these machines really worth it?
91
92 However, ARM6 and up machines allow modules to take multiples of 4k, and
93 as such Acorn RiscPCs and other architectures using these processors can
94 make good use of modularisation.
95
96
97ADFS Image files
98----------------
99
100 You can access image files on your ADFS partitions by mounting the ADFS
101 partition, and then using the loopback device driver. You must have
102 losetup installed.
103
104 Please note that the PCEmulator DOS partitions have a partition table at
105 the start, and as such, you will have to give '-o offset' to losetup.
106
107
108Request to developers
109---------------------
110
111 When writing device drivers which include a separate assembler file, please
112 include it in with the C file, and not the arch/arm/lib directory. This
113 allows the driver to be compiled as a loadable module without requiring
114 half the code to be compiled into the kernel image.
115
116 In general, try to avoid using assembler unless it is really necessary. It
117 makes drivers far less easy to port to other hardware.
118
119
120ST506 hard drives
121-----------------
122
123 The ST506 hard drive controllers seem to be working fine (if a little
124 slowly). At the moment they will only work off the controllers on an
125 A4x0's motherboard, but for it to work off a Podule just requires
126 someone with a podule to add the addresses for the IRQ mask and the
127 HDC base to the source.
128
129 As of 31/3/96 it works with two drives (you should get the ADFS
130 *configure harddrive set to 2). I've got an internal 20MB and a great
131 big external 5.25" FH 64MB drive (who could ever want more :-) ).
132
133 I've just got 240K/s off it (a dd with bs=128k); thats about half of what
134 RiscOS gets; but it's a heck of a lot better than the 50K/s I was getting
135 last week :-)
136
137 Known bug: Drive data errors can cause a hang; including cases where
138 the controller has fixed the error using ECC. (Possibly ONLY
139 in that case...hmm).
140
141
1421772 Floppy
143-----------
144 This also seems to work OK, but hasn't been stressed much lately. It
145 hasn't got any code for disc change detection in there at the moment which
146 could be a bit of a problem! Suggestions on the correct way to do this
147 are welcome.
148
149
150Kernel entry (head-armv.S)
151--------------------------
152 The initial entry into the kernel made via head-armv.S uses architecture
153 independent code. The architecture is selected by the value of 'r1' on
154 entry, which must be kept unique. You can register a new architecture
155 by mailing the following details to rmk@arm.linux.org.uk Please give
156 the mail a subject of 'Register new architecture':
157
158 Name: <name of your architecture>
159 ArchDir: <name of include/asm-arm/arch-* directory>
160 Type: <MACH_TYPE_* macro name>
161 Description:
162 <description of your architecture>
163
164 Please follow this format - it is an automated system. You should
165 receive a reply in short order.
166
167---
168Russell King (26/01/2001)
169