communication between applications and hotplugd

communication between applications and hotplugd

[Joseph Wenninger]

Hi

I'm new to that list, so excuse me, if that has already been asked or 
discussed.

Is there a way an application can communicate directly with the hotplugd, 
instead of just a bunch of scripts ?

I'm implementing an application for KDE, which would need information about 
plugging/unplugging devices, device types and if possibly major/minor device 
numbers (or device node names corresponding with the newly added/removed 
devices). 

I only saw a set of many scripts on my linux installation, but nothing what I 
could use distribution independently.

Is there something, what I missed ?

Kind regards
Joseph Wenninger



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Re: communication between applications and hotplugd

[David Brownell]

> Is there a way an application can communicate directly with the hotplugd, 
> instead of just a bunch of scripts ?

/sbin/hotplug is invoked by the kernel as the way it
reports hotplug events ... there is no "hotplugd".

What you could do is have /sbin/hotplug forward those
events to some application using named pipes or sockets.
That's been discussed as one of the mechanisms by which
the X11 server, for one example, would learn about new
input devices.  Clearly it could work for any kind of
hotplug event.

As for notification about new /dev nodes (char/block
major and minor) ... you might be able to make "devfsd"
do it.  Remember that there's no linkage within the
kernel between the device ids it uses (c/b major/minor)
and the filenames assigned to them in /dev, except for
systems that use devfs.  Until "driverfs" gets more
functional (in 2.5) I suspect some of what you want
is going to be difficult.

- Dave




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Re: communication between applications and hotplugd

[Greg KH]

On Mon, Jul 01, 2002 at 09:47:09PM +0000, Joseph Wenninger wrote:
> 
> I'm implementing an application for KDE, which would need information about 
> plugging/unplugging devices, device types and if possibly major/minor device 
> numbers (or device node names corresponding with the newly added/removed 
> devices). 

driverfs combined with /sbin/hotplug will provide this information to
you in 2.5 soon.  Pat Mochel and I just presented how this will be done
at the 2002 Ottawa Linux Symposium.  I don't know if the talks are
online yet, but later this week, we'll have something written down
and post it to lkml for how it will all work.

Basically driverfs will export the major/minor number for the device,
and /sbin/hotplug will be called when the device shows up or disappears.
With this, devfs is no longer needed, and all of the naming policy can
move to userspace.  More details later, I'm supposed to be on vacation
right now :)

thanks,

greg k-h


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