Re: Another udev/sysfs question.

[Greg KH <greg@kroah.com>]

On Sat, Nov 18, 2006 at 08:02:53PM -0600, Kilau, Scott wrote:
> Hi Greg, all, 
> 
> > What are you really trying to express here in sysfs?  And why do you
> > need to have a new class for your device, shouldn't it be a 
> > real device and not a class?
> 
> 
> This driver I am trying to port to sysfs is "different" compared to
> most serial drivers.
> 
> In all our serial drivers, we have a PCI board, with many ports on it.
> That is obviously very easy to express is sysfs, and all those drivers
> have now been ported to use sysfs instead of proc.
> 
> This driver, called RealPort, is a different beast.
> 
> Ultimately it's a serial driver, so eventually I have a bunch of ttys
> that are exported to /sys/class/tty.
> 
> But these serial ports doesn't have a PCI board as its parent.
> Instead, the ttys are actually located all around the
> network on embedded systems over the network, whether
> it be ethernet, wireless, cellular, etc, etc.
> 
> So the tree I have is something like:
> Driver -> Network -> Embedded system out on the network somewhere ->
> serial ports.

Heh, that looks like a fun type of device :)

> The idea I wanted to do with this and sysfs, was to have a tree looking
> like:
> /sys/class/digi_realport/node[X]/tty[XYZ]
> 
> In fact, I was thinking that the tty[XYZ] values would actually be
> symlinks
> pointing back up to /sys/class/tty/*, which can be done, I think?

No, don't play with classes at all here.

What you need is a real device, just hang it off of the device that you
need to.

For example, your network device could just go at:
	/sys/devices/pci0000:00/0000:00:02.0/0000:01:00.2/0000:03:0e.0/eth0/realportX
where realportX is your device.

> The trouble here is that I want to express the "Node[X]" values as a
> class.

Why?

> Its not really a device, because its not something that can be used by
> anyone...
> (ie, it is not addressable by a /dev entry or anything)

That doesn't matter, devices don't have /dev entries, classes do :)

> I currently have made it class_device with a devt of MKDEV(0,0) which is
> close
> to what I want, but it still builds a couple file entries into the
> directory
> where I really don't want anything...
> 
> Sorry this email was so long, I just wanted to make sure I design this
> correctly in the true spirit of "sysfs".
> 
> (Its currently using /proc, with this same tree, so I was hoping I could
> completely
> ditch using /proc from the driver...)

Yes, you don't want to use /proc for this kind of thing...

Hope this helps,

greg k-h

-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CIDÞVDEV
_______________________________________________
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