Memory in linux

In a typical 32 bit machine, the address ranges from 0x00000000  to 2^32 – 1 (0xFFFFFFFF) . This entire address region will be split among RAM and device regions (address of devices and its registers)

/proc/meminfo will list the memory maps in the device.

In general, addresses which are mapped to RAM is known as physical address, where as address which are mapped to devices are known as bus address. The address can be architecture dependent and the details can be obtained from hardware manufacturer .

However none of these address can be used directly from a linux module. Physical address needs to be mapped to a virtual address to make use of it

sample output
abhi :# cat /proc/iomem 
00000000-0009f7ff : System RAM
0009f800-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000ca000-000cafff : Adapter ROM
000dc000-000e3fff : reserved
000f0000-000fffff : System ROM
00100000-3feeffff : System RAM
  00100000-002baebc : Kernel code
  002baebd-0037661f : Kernel data
  003bc000-0041f57f : Kernel bss
3fef0000-3fefefff : ACPI Tables
3feff000-3fefffff : ACPI Non-volatile Storage
3ff00000-3fffffff : System RAM
50000000-50007fff : 0000:00:0f.0
50008000-5000bfff : 0000:00:10.0
d0000000-d7ffffff : 0000:00:0f.0
d8000000-d87fffff : 0000:00:0f.0
d8800000-d881ffff : 0000:00:10.0
  d8800000-d881ffff : mpt
d8820000-d883ffff : 0000:00:10.0
  d8820000-d883ffff : mpt
d8900000-d9cfffff : PCI Bus 0000:02
  d8900000-d8900fff : 0000:02:03.0
    d8900000-d8900fff : ehci_hcd
d9d00000-d9dfffff : PCI Bus 0000:03
d9e00000-d9efffff : PCI Bus 0000:0b
d9f00000-d9ffffff : PCI Bus 0000:13
da000000-da0fffff : PCI Bus 0000:1b
da100000-da1fffff : PCI Bus 0000:04
da200000-da2fffff : PCI Bus 0000:0c
da300000-da3fffff : PCI Bus 0000:14
da400000-da4fffff : PCI Bus 0000:1c
da500000-da5fffff : PCI Bus 0000:05
da600000-da6fffff : PCI Bus 0000:0d
da700000-da7fffff : PCI Bus 0000:15
da800000-da8fffff : PCI Bus 0000:1d
da900000-da9fffff : PCI Bus 0000:06
daa00000-daafffff : PCI Bus 0000:0e
dab00000-dabfffff : PCI Bus 0000:16
dac00000-dacfffff : PCI Bus 0000:1e
dad00000-dadfffff : PCI Bus 0000:07
dae00000-daefffff : PCI Bus 0000:0f
daf00000-daffffff : PCI Bus 0000:17
db000000-db0fffff : PCI Bus 0000:1f
db100000-db1fffff : PCI Bus 0000:08
db200000-db2fffff : PCI Bus 0000:10
db300000-db3fffff : PCI Bus 0000:18
db400000-db4fffff : PCI Bus 0000:20
db500000-db5fffff : PCI Bus 0000:09
db600000-db6fffff : PCI Bus 0000:11
db700000-db7fffff : PCI Bus 0000:19
db800000-db8fffff : PCI Bus 0000:21
db900000-db9fffff : PCI Bus 0000:0a
dba00000-dbafffff : PCI Bus 0000:12
dbb00000-dbbfffff : PCI Bus 0000:1a
dbc00000-dbcfffff : PCI Bus 0000:22
dbe00000-dbffffff : pnp 00:0c
dc400000-dc9fffff : PCI Bus 0000:02
  dc400000-dc40ffff : 0000:02:01.0
dca00000-dcafffff : PCI Bus 0000:03
dcb00000-dcbfffff : PCI Bus 0000:0b
dcc00000-dccfffff : PCI Bus 0000:13
dcd00000-dcdfffff : PCI Bus 0000:1b
dce00000-dcefffff : PCI Bus 0000:04
dcf00000-dcffffff : PCI Bus 0000:0c
dd000000-dd0fffff : PCI Bus 0000:14
dd100000-dd1fffff : PCI Bus 0000:1c
dd200000-dd2fffff : PCI Bus 0000:05
dd300000-dd3fffff : PCI Bus 0000:0d
dd400000-dd4fffff : PCI Bus 0000:15
dd500000-dd5fffff : PCI Bus 0000:1d
dd600000-dd6fffff : PCI Bus 0000:06
dd700000-dd7fffff : PCI Bus 0000:0e
dd800000-dd8fffff : PCI Bus 0000:16
dd900000-dd9fffff : PCI Bus 0000:1e
dda00000-ddafffff : PCI Bus 0000:07
ddb00000-ddbfffff : PCI Bus 0000:0f
ddc00000-ddcfffff : PCI Bus 0000:17
ddd00000-dddfffff : PCI Bus 0000:1f
dde00000-ddefffff : PCI Bus 0000:08
ddf00000-ddffffff : PCI Bus 0000:10
de000000-de0fffff : PCI Bus 0000:18
de100000-de1fffff : PCI Bus 0000:20
de200000-de2fffff : PCI Bus 0000:09
de300000-de3fffff : PCI Bus 0000:11
de400000-de4fffff : PCI Bus 0000:19
de500000-de5fffff : PCI Bus 0000:21
de600000-de6fffff : PCI Bus 0000:0a
de700000-de7fffff : PCI Bus 0000:12
de800000-de8fffff : PCI Bus 0000:1a
de900000-de9fffff : PCI Bus 0000:22
e0000000-efffffff : PCI MMCONFIG 0
  e0000000-efffffff : reserved
fec00000-fec0ffff : reserved
fee00000-fee00fff : reserved
fffe0000-ffffffff : reserved