implementing hotplug event

implementing hotplug event

[Jon Smirl]

My driver can catch $ACTION now. I also added the code to my class driver to
make it send out the same info as a PCI hotplug event. Now my userspace app
needs to open the newly loaded device driver, how do I reliably find it? I know
that it is at /dev/dri/cardX but what if the user is replacing /dev with /udev
or /devfs? I know the major/minor I could just mknode in my program too.

==Jon Smirl
jonsmirl@yahoo.com

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Re: implementing hotplug event

[Greg KH]

On Sun, Dec 28, 2003 at 09:19:41PM -0800, Jon Smirl wrote:
> My driver can catch $ACTION now.

You mean your userspace program, right?

> I also added the code to my class driver to make it send out the same
> info as a PCI hotplug event.

That's good.

> Now my userspace app needs to open the newly loaded device driver, how
> do I reliably find it? I know that it is at /dev/dri/cardX but what if
> the user is replacing /dev with /udev or /devfs? I know the
> major/minor I could just mknode in my program too.

To be safe, you can always just read the sysfs "dev" file, and do a
mknod with that information.  Otherwise you could query udev as to what
it has named your device, but we don't have those hooks in udev just
yet...  someday soon...

thanks,

greg k-h


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Re: implementing hotplug event

[Jon Smirl]

--- Greg KH <greg@kroah.com> wrote:
> > Now my userspace app needs to open the newly loaded device driver, how
> > do I reliably find it? I know that it is at /dev/dri/cardX but what if
> > the user is replacing /dev with /udev or /devfs? I know the
> > major/minor I could just mknode in my program too.
> 
> To be safe, you can always just read the sysfs "dev" file, and do a
> mknod with that information.  Otherwise you could query udev as to what
> it has named your device, but we don't have those hooks in udev just
> yet...  someday soon...

I just sent the major/minor to the hotplug event in the environment variables,
it seemed easier than sending out the slot id and finding "dev" in sysfs. Doing
mknod from the user space app seems to be the most reliable scheme.



==Jon Smirl
jonsmirl@yahoo.com

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Re: implementing hotplug event

[Greg KH]

On Mon, Dec 29, 2003 at 05:48:51PM -0800, Jon Smirl wrote:
> --- Greg KH <greg@kroah.com> wrote:
> > > Now my userspace app needs to open the newly loaded device driver, how
> > > do I reliably find it? I know that it is at /dev/dri/cardX but what if
> > > the user is replacing /dev with /udev or /devfs? I know the
> > > major/minor I could just mknode in my program too.
> > 
> > To be safe, you can always just read the sysfs "dev" file, and do a
> > mknod with that information.  Otherwise you could query udev as to what
> > it has named your device, but we don't have those hooks in udev just
> > yet...  someday soon...
> 
> I just sent the major/minor to the hotplug event in the environment variables,
> it seemed easier than sending out the slot id and finding "dev" in sysfs. Doing
> mknod from the user space app seems to be the most reliable scheme.

True, as long as your userapp is running as root :)

thanks,

greg k-h


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