1Kernel initialisation parameters on ARM Linux
2---------------------------------------------
3
4The following document describes the kernel initialisation parameter
5structure, otherwise known as 'struct param_struct' which is used
6for most ARM Linux architectures.
7
8This structure is used to pass initialisation parameters from the
9kernel loader to the Linux kernel proper, and may be short lived
10through the kernel initialisation process.  As a general rule, it
11should not be referenced outside of arch/arm/kernel/setup.c:setup_arch().
12
13There are a lot of parameters listed in there, and they are described
14below:
15
16 page_size
17
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
22
23   This is the total number of pages of memory in the system.  If
24   the memory is banked, then this should contain the total number
25   of pages in the system.
26
27   If the system contains separate VRAM, this value should not
28   include this information.
29
30 ramdisk_size
31
32   This is now obsolete, and should not be used.
33
34 flags
35
36   Various kernel flags, including:
37    bit 0 - 1 = mount root read only
38    bit 1 - unused
39    bit 2 - 0 = load ramdisk
40    bit 3 - 0 = prompt for ramdisk
41
42 rootdev
43
44   major/minor number pair of device to mount as the root filesystem.
45
46 video_num_cols
47 video_num_rows
48
49   These two together describe the character size of the dummy console,
50   or VGA console character size.  They should not be used for any other
51   purpose.
52
53   It's generally a good idea to set these to be either standard VGA, or
54   the equivalent character size of your fbcon display.  This then allows
55   all the bootup messages to be displayed correctly.
56
57 video_x
58 video_y
59
60   This describes the character position of cursor on VGA console, and
61   is otherwise unused. (should not be used for other console types, and
62   should not be used for other purposes).
63
64 memc_control_reg
65
66   MEMC chip control register for Acorn Archimedes and Acorn A5000
67   based machines.  May be used differently by different architectures.
68
69 sounddefault
70
71   Default sound setting on Acorn machines.  May be used differently by
72   different architectures.
73
74 adfsdrives
75
76   Number of ADFS/MFM disks.  May be used differently by different
77   architectures.
78
79 bytes_per_char_h
80 bytes_per_char_v
81
82   These are now obsolete, and should not be used.
83
84 pages_in_bank[4]
85
86   Number of pages in each bank of the systems memory (used for RiscPC).
87   This is intended to be used on systems where the physical memory
88   is non-contiguous from the processors point of view.
89
90 pages_in_vram
91
92   Number of pages in VRAM (used on Acorn RiscPC).  This value may also
93   be used by loaders if the size of the video RAM can't be obtained
94   from the hardware.
95
96 initrd_start
97 initrd_size
98
99   This describes the kernel virtual start address and size of the
100   initial ramdisk.
101
102 rd_start
103
104   Start address in sectors of the ramdisk image on a floppy disk.
105
106 system_rev
107
108   system revision number.
109
110 system_serial_low
111 system_serial_high
112
113   system 64-bit serial number
114
115 mem_fclk_21285
116
117   The speed of the external oscillator to the 21285 (footbridge),
118   which control's the speed of the memory bus, timer & serial port.
119   Depending upon the speed of the cpu its value can be between
120   0-66 MHz. If no params are passed or a value of zero is passed,
121   then a value of 50 Mhz is the default on 21285 architectures.
122
123 paths[8][128]
124
125   These are now obsolete, and should not be used.
126
127 commandline
128
129   Kernel command line parameters.  Details can be found elsewhere.
130