Chip Salzenberg wrote:

> According to Alan Cox:
> > Given a file handle 'X' how do I find out what ioctl groups I should
> > apply to it.
>
> Wouldn't it be better just to *try* ioctls and see which ones work and
> which ones don't?

As ioctl's is just numbers that can be valid but mean totally different thing 
depending on device I don't see how this is going to work. It took me close to a month 
to figure out why my new 10000rpm scsi disk constantly ended up with a read only 
filesystem. What I did not know at that time was that the /dev/sg[x] numbering was 
changed by adding something to the scsi chain and my backup software now sent the 
eject command to the disk instead of to the tape. This ioctl means spinn down when it 
is sent to the disk and that in turn produces a fatal error and a remount to ro for 
the mounted filesystem.

This problem had not existed for me if things had been mapped more static this i why 
I'am not overly happy hearing that things is going to be even more volatile. But I 
guess that it's possible to solve most of this issues in userspace.

One way of looking on the problem is to take it to it's logical extrem. This would be 
a kernel with no persistent storage for devices no major,minor and no name policy. The 
kernel would simply put any device it finds in /dev/devno/[x] where x is just a number 
that should be seen as something that changed for every reboot.

Any userspace solution that can create device links that are stable out of this is one 
that would get my vote. This obviously needs some type if standard why to query the 
devices or else it's no way it can work.


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