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Based on kernel version 3.16. Page generated on 2014-08-06 21:36 EST.

1	Kernel initialisation parameters on ARM Linux
2	---------------------------------------------
3	
4	The following document describes the kernel initialisation parameter
5	structure, otherwise known as 'struct param_struct' which is used
6	for most ARM Linux architectures.
7	
8	This structure is used to pass initialisation parameters from the
9	kernel loader to the Linux kernel proper, and may be short lived
10	through the kernel initialisation process.  As a general rule, it
11	should not be referenced outside of arch/arm/kernel/setup.c:setup_arch().
12	
13	There are a lot of parameters listed in there, and they are described
14	below:
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.
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