Re: Which node has the device been bound to?

[Oliver Neukum <oliver@neukum.name>]

Am Montag, 3. Juni 2002 23:58 schrieb Greg KH:
> On Mon, Jun 03, 2002 at 11:09:36PM +0200, Oliver Neukum wrote:
> > > But what is the real problem here?  What do you want to solve? 
> > > Mapping of a /dev node to a physical device?  Or mapping of a
> > > physical device to a /dev node?  Or something else?
> >
> > The former. The latter has some principal problems.
> > To do the former you need to have an atomic operation on an
> > opened device.
> > Thus you need to have the device node open and you need
> > the ioctl to not return a pointer to a driverfs file. You either
> > return its content or an fd.
>
> Ok, I understand a bit better now (sorry, I'm slow today...).  So what
> fd do you want returned in the ioctl()?  driverfs implements a tree for
> every device, not a single file.  Do you want a fd for the directory?

No problem, I am dense at times, too.
There's a problem. You cannot open() based on a directory fd,
unless I am mistaken.
I can't come up with anything better than a set of ioctls that return
the contents of the individual files. And I know that this is ugly.
I don't claim that this is a good solution, just that it's the only
solution I have and that there's a race otherwise.
You simply cannot use names, thus parsing files for the name of the
node won't work.

I've thought about finding the device node to a physical device.
It really is problematic. Firstly there can be several nodes.
Secondly you'd need device nodes in driverfs, in effect merging it
with devfs.

	Regards
		Oliver


_______________________________________________________________

Don't miss the 2002 Sprint PCS Application Developer's Conference
August 25-28 in Las Vegas -- http://devcon.sprintpcs.com/adp/index.cfm

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel