[systemd-devel] Need help with a systemd/mdadm interaction.

[NeilBrown]

On Tue, 12 Nov 2013 18:16:24 +0900 Greg KH <gregkh at linuxfoundation.org> wrote:

> On Tue, Nov 12, 2013 at 07:54:42PM +1100, NeilBrown wrote:
> > On Tue, 12 Nov 2013 00:10:28 -0800 Greg KH <gregkh at linuxfoundation.org> wrote:
> > 
> > > On Tue, Nov 12, 2013 at 11:31:45AM +1100, NeilBrown wrote:
> > > > Alternately, is there some "all devices have been probed, nothing new will
> > > > appear unless it is hot-plugged" event.  That would be equally useful (and
> > > > probably mirrors what hardware-RAID cards do).
> > > 
> > > No, there's no way to ever know this in a hotplug world, sorry.
> > > Especially with USB devices, they show up when they show up, there's no
> > > "oh look, the bus is all scanned now and all devices currently plugged
> > > in are found" type knowledge at all.
> > > 
> > > Then there are hotplug PCI systems where people slam in PCI cards
> > > whenever they feel like it (remember, thunderbolt is PCI express...)
> > > 
> > > Sorry,
> > > 
> > > greg k-h
> > 
> > Surely something must be possible.
> 
> For USB, nope, there isn't, sorry.
> 
> > Clearly a physical hot-plug event will cause more devices to appear, but
> > there must come a point at which no more (non-virtual) devices will appear
> > unless a physical event happens?
> 
> Not for USB, sorry.
> 
> The USB bus just announces devices when it finds them, there is no "all
> is quiet" type signal or detection.
> 
> Same for PCI hotplug, devices can show up at any point in time, you
> never know when, and you don't know when all devices are "found".
> 
> sorry,
> 
> greg k-h


Hmmm... OK.  USB doesn't bother me a lot, but PCI is important.

I guess I'll just have to settle for a timeout much like the current
device-discovery timeout that systemd has.
Still hoping someone can tell me how to plug into that though...

Thanks,
NeilBrown
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