1 ARM Linux 2.6 2 ============= 3 4 Please check <ftp://ftp.arm.linux.org.uk/pub/armlinux> for 5 updates. 6 7Compilation 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 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. 14 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. 19 20 If you wish to cross-compile, then alter the following lines in the top 21 level make file: 22 23 ARCH = <whatever> 24 with 25 ARCH = arm 26 27 and 28 29 CROSS_COMPILE= 30 to 31 CROSS_COMPILE=<your-path-to-your-compiler-without-gcc> 32 eg. 33 CROSS_COMPILE=arm-linux- 34 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'. 38 39 40Bug reports etc 41--------------- 42 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. 46 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/ 50 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. 54 55 56Include files 57------------- 58 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: 62 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) 68 69 70Machine/Platform support 71------------------------ 72 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 $(MACHINE) to refer to the category) 78 79 To this end, we now have arch/arm/mach-$(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. 84 85 86Modules 87------- 88 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? 93 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. 97 98 99ADFS Image files 100---------------- 101 102 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. 105 106 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. 108 109 110Request to developers 111--------------------- 112 113 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. 117 118 In general, try to avoid using assembler unless it is really necessary. It 119 makes drivers far less easy to port to other hardware. 120 121 122ST506 hard drives 123----------------- 124 125 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. 130 131 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 :-) ). 134 135 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 :-) 138 139 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). 142 143 1441772 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. 150 151 152CONFIG_MACH_ and CONFIG_ARCH_ 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. 160 161 Previous registrations may be found online. 162 163 <http://www.arm.linux.org.uk/developer/machines/> 164 165Kernel 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. 170 171 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. 174 175 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. 182 183 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." 187 188 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. 192 193 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: 197 198 <http://www.arm.linux.org.uk/developer/machines/> 199 200 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. 202 203--- 204Russell King (15/03/2004) 205