major and minor numbers in Linux

[Rumen Ginev]

Hi,

In HP-UX major number of a device file represents the device driver in the kernel and from the minor number one can extracts the hw path of the device.
What do major and minor numbers in Linux mean? What information they can bring for us?

Thanks,
Rumen

[Vincent Fleming · Accepted solution]

The same.

The major number is the slot in the devsw tables in the kernel that the driver occupies. The two tables b_devsw and c_devsw are the block and character device switch tables. Block device file major numbers are actually an index into the b_devsw table, and similarly, character device major numbers are index into the c_devsw table.

The minor numbers, by definition, are defined by the driver itself. Check the man pages for the particular device driver to find out what the minor numbers mean. Typically they indicate a unique subdevice, such as a bus, id, and lun for scsi devices. Some devices, such as ptys, the devices are simply numbered 1, 2, 3, 4, etc. They can mean anything the device driver writer desires.

Have fun

[Kodjo Agbenu]

Hello,

Just an additional information : in Linux, you can find the list of minor numbers and their meanings in the kernel documentation. If installed in your system, check /usr/src/linux/Documentation/devices.txt. Otherwise :

http://www.linuxhq.com/kernel/v2.4/doc/devices.txt.html

Good luck.

Kodjo

[Rumen Ginev]

Sorry for the late points assignment.

Kodjo, I now about devices.txt document. It is very useful in case of recreating lost device files. In this document one can find major and minor numbers for almost every device file, but can not find the answer of my question.

Regards,

Rumen

[Andrea Rossi]

cat /proc/devices