Re: Which node has the device been bound to?

[Oliver Neukum <Oliver.Neukum@lrz.uni-muenchen.de>]

> > Do you think that it's wise to introduce yet another driver
> > specific file ?
>
> Not really, but it follows the way _all_ other tty drivers do it :)

Oh well.

> > > The driverfs changes that are slowly going into the tree might
> > > eventually help you out.  Check out the changes that will be in 2.5.20
> > > for the usb tree (they look much like the pci tree in 2.5.19 if you
> > > want to compare that right now.)
> > >
> > > And how would you be able to determine uniquely each iPAQ anyway?  Do
> > > they have unique USB serial numbers or would you want to determine the
> > > device based on the physical USB port it is plugged into on the host?
> >
> > You might not like it, but I still think that a standard ioctl() would
> > be the best way to export such information. Could you enlighten
> > me on how you want to make sure that the information you act on
> > is guaranteed to be current, if you do not base the mechanism
> > on the opened device ?
>
> Have you seen the way driverfs shows the usb and pci topology?

Fine for humans, which is not the issue here.

> And yes, you might be acting on old data.  But if you have an ioctl()
> what would it return?  A pointer to the topology location which might
> have just changed?  I don't see how an ioctl() can solve this problem
> any different from the way driverfs is going about it.  But I could be
> missing something. :)

An ioctl() would either return the actual topology information
or a unique token.

A name can change meaning. An open file cannot. It'll either
be what the ioctl() will tell you, or it'll be gone. If you operate on a
device that is gone the kernel will return an error and all is well.

If you parse what driverfs gives you, you operate on changing
data without a lock. I can see no way to change that.

	Regards
		Oliver

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