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- =============================================
- Kernel initialisation parameters on ARM Linux
- =============================================
- The following document describes the kernel initialisation parameter
- structure, otherwise known as 'struct param_struct' which is used
- for most ARM Linux architectures.
- This structure is used to pass initialisation parameters from the
- kernel loader to the Linux kernel proper, and may be short lived
- through the kernel initialisation process. As a general rule, it
- should not be referenced outside of arch/arm/kernel/setup.c:setup_arch().
- There are a lot of parameters listed in there, and they are described
- below:
- page_size
- This parameter must be set to the page size of the machine, and
- will be checked by the kernel.
- nr_pages
- This is the total number of pages of memory in the system. If
- the memory is banked, then this should contain the total number
- of pages in the system.
- If the system contains separate VRAM, this value should not
- include this information.
- ramdisk_size
- This is now obsolete, and should not be used.
- flags
- Various kernel flags, including:
- ===== ========================
- bit 0 1 = mount root read only
- bit 1 unused
- bit 2 0 = load ramdisk
- bit 3 0 = prompt for ramdisk
- ===== ========================
- rootdev
- major/minor number pair of device to mount as the root filesystem.
- video_num_cols / video_num_rows
- These two together describe the character size of the dummy console,
- or VGA console character size. They should not be used for any other
- purpose.
- It's generally a good idea to set these to be either standard VGA, or
- the equivalent character size of your fbcon display. This then allows
- all the bootup messages to be displayed correctly.
- video_x / video_y
- This describes the character position of cursor on VGA console, and
- is otherwise unused. (should not be used for other console types, and
- should not be used for other purposes).
- memc_control_reg
- MEMC chip control register for Acorn Archimedes and Acorn A5000
- based machines. May be used differently by different architectures.
- sounddefault
- Default sound setting on Acorn machines. May be used differently by
- different architectures.
- adfsdrives
- Number of ADFS/MFM disks. May be used differently by different
- architectures.
- bytes_per_char_h / bytes_per_char_v
- These are now obsolete, and should not be used.
- pages_in_bank[4]
- Number of pages in each bank of the systems memory (used for RiscPC).
- This is intended to be used on systems where the physical memory
- is non-contiguous from the processors point of view.
- pages_in_vram
- Number of pages in VRAM (used on Acorn RiscPC). This value may also
- be used by loaders if the size of the video RAM can't be obtained
- from the hardware.
- initrd_start / initrd_size
- This describes the kernel virtual start address and size of the
- initial ramdisk.
- rd_start
- Start address in sectors of the ramdisk image on a floppy disk.
- system_rev
- system revision number.
- system_serial_low / system_serial_high
- system 64-bit serial number
- mem_fclk_21285
- The speed of the external oscillator to the 21285 (footbridge),
- which control's the speed of the memory bus, timer & serial port.
- Depending upon the speed of the cpu its value can be between
- 0-66 MHz. If no params are passed or a value of zero is passed,
- then a value of 50 Mhz is the default on 21285 architectures.
- paths[8][128]
- These are now obsolete, and should not be used.
- commandline
- Kernel command line parameters. Details can be found elsewhere.
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