mknod minor

shanenin · 04-01-2005, 09:56 PM

I have been messing around with tv out using my matrox card. The tutorial I mainly used said to use the command
mknod /dev/fusion/0 c 253 0
this worked for my older system using a 2.4 kernel(2.4 headers), but not my newer system using a 2.6(and 2.6 headers). For the newer system I had to use this command
mknod /dev/fusion/0 c 252 0 #notice the minor is a different number

notice the number, 252(I think this is the minor), where does that number come from?

rnturn · 04-01-2005, 10:30 PM

Looks like on 2.4 you were creating a character device with a major number of 253 and, then, on 2.6 that changed to a major number of 252.

According to the "devices.txt" file in /usr/src/linux/Documentation, those number fall into the range, well, here's what's in the file:

Code:

240-254 char    LOCAL/EXPERIMENTAL USE
240-254 block   LOCAL/EXPERIMENTAL USE
                Allocated for local/experimental use.  For devices not
                assigned official numbers, these ranges should be
                used in order to avoid conflicting with future assignments.

You have to contact Matrox to find out why they changed major numbers. Perhaps they found that some other popular device manufacturer was using 252 under 2.6 before they got their driver ported/updated. Kinda hard to say why they changed it. Pity they didn't update their documentation/tutorial. Or, if that's a third-party tutorial, then that author never got it updated in time.

shanenin · 04-01-2005, 10:34 PM

thanks for the explanation.