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.