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1da177e4 | 2 | Kernel initialisation parameters on ARM Linux |
dc7a12bd | 3 | ============================================= |
1da177e4 LT |
4 | |
5 | The following document describes the kernel initialisation parameter | |
6 | structure, otherwise known as 'struct param_struct' which is used | |
7 | for most ARM Linux architectures. | |
8 | ||
9 | This structure is used to pass initialisation parameters from the | |
10 | kernel loader to the Linux kernel proper, and may be short lived | |
11 | through the kernel initialisation process. As a general rule, it | |
12 | should not be referenced outside of arch/arm/kernel/setup.c:setup_arch(). | |
13 | ||
14 | There are a lot of parameters listed in there, and they are described | |
15 | below: | |
16 | ||
17 | page_size | |
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18 | This parameter must be set to the page size of the machine, and |
19 | will be checked by the kernel. | |
20 | ||
21 | nr_pages | |
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22 | This is the total number of pages of memory in the system. If |
23 | the memory is banked, then this should contain the total number | |
24 | of pages in the system. | |
25 | ||
26 | If the system contains separate VRAM, this value should not | |
27 | include this information. | |
28 | ||
29 | ramdisk_size | |
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30 | This is now obsolete, and should not be used. |
31 | ||
32 | flags | |
1da177e4 | 33 | Various kernel flags, including: |
1da177e4 | 34 | |
dc7a12bd MCC |
35 | ===== ======================== |
36 | bit 0 1 = mount root read only | |
37 | bit 1 unused | |
38 | bit 2 0 = load ramdisk | |
39 | bit 3 0 = prompt for ramdisk | |
40 | ===== ======================== | |
1da177e4 | 41 | |
dc7a12bd | 42 | rootdev |
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43 | major/minor number pair of device to mount as the root filesystem. |
44 | ||
dc7a12bd | 45 | video_num_cols / video_num_rows |
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46 | These two together describe the character size of the dummy console, |
47 | or VGA console character size. They should not be used for any other | |
48 | purpose. | |
49 | ||
50 | It's generally a good idea to set these to be either standard VGA, or | |
51 | the equivalent character size of your fbcon display. This then allows | |
52 | all the bootup messages to be displayed correctly. | |
53 | ||
dc7a12bd | 54 | video_x / video_y |
1da177e4 | 55 | This describes the character position of cursor on VGA console, and |
13fce806 | 56 | is otherwise unused. (should not be used for other console types, and |
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57 | should not be used for other purposes). |
58 | ||
59 | memc_control_reg | |
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60 | MEMC chip control register for Acorn Archimedes and Acorn A5000 |
61 | based machines. May be used differently by different architectures. | |
62 | ||
63 | sounddefault | |
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64 | Default sound setting on Acorn machines. May be used differently by |
65 | different architectures. | |
66 | ||
67 | adfsdrives | |
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68 | Number of ADFS/MFM disks. May be used differently by different |
69 | architectures. | |
70 | ||
dc7a12bd | 71 | bytes_per_char_h / bytes_per_char_v |
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72 | These are now obsolete, and should not be used. |
73 | ||
74 | pages_in_bank[4] | |
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75 | Number of pages in each bank of the systems memory (used for RiscPC). |
76 | This is intended to be used on systems where the physical memory | |
77 | is non-contiguous from the processors point of view. | |
78 | ||
79 | pages_in_vram | |
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80 | Number of pages in VRAM (used on Acorn RiscPC). This value may also |
81 | be used by loaders if the size of the video RAM can't be obtained | |
82 | from the hardware. | |
83 | ||
dc7a12bd | 84 | initrd_start / initrd_size |
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85 | This describes the kernel virtual start address and size of the |
86 | initial ramdisk. | |
87 | ||
88 | rd_start | |
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89 | Start address in sectors of the ramdisk image on a floppy disk. |
90 | ||
91 | system_rev | |
1da177e4 LT |
92 | system revision number. |
93 | ||
dc7a12bd | 94 | system_serial_low / system_serial_high |
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95 | system 64-bit serial number |
96 | ||
97 | mem_fclk_21285 | |
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98 | The speed of the external oscillator to the 21285 (footbridge), |
99 | which control's the speed of the memory bus, timer & serial port. | |
100 | Depending upon the speed of the cpu its value can be between | |
101 | 0-66 MHz. If no params are passed or a value of zero is passed, | |
102 | then a value of 50 Mhz is the default on 21285 architectures. | |
103 | ||
104 | paths[8][128] | |
1da177e4 LT |
105 | These are now obsolete, and should not be used. |
106 | ||
107 | commandline | |
1da177e4 | 108 | Kernel command line parameters. Details can be found elsewhere. |