Linux device drivers...followup...

Jerry Feldman Gerry.Feldman at
Tue Feb 22 09:36:34 EST 2000

I think this was answered previously.
In Unix and Linux, the files normally found in /dev (but not required to be 
in that directory) are called device special files created by the 
/sbin/mknod command. All they do is to convey the type of device (b == 
block, c == character, p == pipe) and major number to the operating 
system (Unix (all flavors), Linux, BSD). The minor number is determined 
by the device driver. Some systems also include and instance number 
which refers to the physical interface board. The device driver uses the 
numbers passed to it to determine which unit to select, and also 
possibly what to do with the unit. For instance, tape devices normally 
have a couple of special files, One would tell the device to rewind on 
close and the other not to rewind on close. Floppies use it to determine 
the type of device, and/or the type of media. You can certainly use a 
720K 3.5 in floppy in a 1.44 drive. /dev/fd0 would be fine for a formatted 
floppy, but you might need to use /dev/fd0D720 if you wanted to format 
the floppy. 

On 22 Feb 00, at 7:47, Pedro Soria-Rodriguez wrote:

> 	Nope...  the entries in /dev are "files" created at some
> point.  
Jerry Feldman
Contractor, eInfrastructure Partner Engineering   

Compaq Computer Corp.
200 Forest Street MRO1-3/F1
Marlboro, Ma. 01752
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