Editing Solaris 10 System Administration Part I (section)

==== device files ====

device file provides access to a device

When using long listing on file the size field is populated by two numbers separated by comma

The two numbers are called major & minor device numbers

major device # identifies the specific device driver required to access device
minor device # identifies specific unit of the type that the device driver controls

Long listing:
<pre>bash-3.00$ ls -l | grep pci
drwxr-xr-x   4 root     sys          512 May  3 16:25 pci@1c,600000
crw-------   1 root     sys      109, 767 Jul 14 16:50 pci@1c,600000:devctl
crw-------   1 root     sys      109, 764 Jul 14 16:50 pci@1c,600000:intr
crw-------   1 root     sys      109, 765 Jul 14 16:50 pci@1c,600000:reg
drwxr-xr-x   5 root     sys          512 May  3 16:25 pci@1d,700000
crw-------   1 root     sys      109, 1023 Jul 14 16:50 pci@1d,700000:devctl
crw-------   1 root     sys      109, 1020 Jul 14 16:50 pci@1d,700000:intr
crw-------   1 root     sys      109, 1021 Jul 14 16:50 pci@1d,700000:reg
drwxr-xr-x   6 root     sys          512 May  3 16:25 pci@1e,600000
crw-------   1 root     sys      109, 511 Jul 14 16:50 pci@1e,600000:devctl
crw-------   1 root     sys      109, 508 Jul 14 16:50 pci@1e,600000:intr
crw-------   1 root     sys      109, 509 Jul 14 16:50 pci@1e,600000:reg
drwxr-xr-x   4 root     sys          512 May  3 16:25 pci@1f,700000
crw-------   1 root     sys      109, 255 Jul 14 16:50 pci@1f,700000:devctl
crw-------   1 root     sys      109, 252 Jul 14 16:50 pci@1f,700000:intr
crw-------   1 root     sys      109, 253 Jul 14 16:50 pci@1f,700000:reg</pre>

'''File pci@1c,600000:devctl refers to major device # 109 & minor device # 767'''

You can also use the <code>file</code> command:
<pre>bash-3.00$ file pci@1c,600000:devctl
pci@1c,600000:devctl:   character special (109/767)</pre>

Use <code>devfsadm</code> command to create new device files

A relationship exists between device file & device it controls. Major & minor device #s contained in inode establish relationship

<image showing relationship from above example>

Verify device driver is available as kernel module:
<pre>bash-3.00# modinfo -w | grep -w scsi
 22  1313a40  122a8   -   1  scsi (SCSI Bus Utility Routines)
bash-3.00# modinfo -c | grep -w scsi
 22          1 scsi                             LOADED/INSTALLED
bash-3.00# modinfo -w | grep -w iscsi            
 96 7b600000  328c8 279   1  iscsi (Sun iSCSI Initiator v20100714-0)
bash-3.00# modinfo -c | grep -w iscsi
 96          1 iscsi                            LOADED/INSTALLED</pre>

device files are categorized as character-special [character or raw devices] or block-special devices [block devices]

device files in each category interact with devices differently

===== character-special device files =====

File type of "c" is character-special device file & data is accessed as a data stream

<pre>crw-------   1 root     sys      109, 767 Jul 14 16:50 pci@1c,600000:devctl</pre>

Result of <code>file</code> command:
<pre>bash-3.00# file pci@1c,600000:devctl
pci@1c,600000:devctl:   character special (109/767)</pre>

===== block-special device files =====

File type of "b" is a block-special device file & for disk devices, block-special device files call for I/O operations based on a defined block size

Block size depends on particular device file

<example of long listing of block file>

data transferred between process & block-special device is first stored in kernel-managed memory-based cache

block devices allow random seeks to be performed [character devices do not]