From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH v4 19/21] drivers/of: Support adding sub-tree
Date: Thu, 14 May 2015 17:47:32 +1000
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To: Pantelis Antoniou <panto-wVdstyuyKrO8r51toPun2/C9HSW9iNxf@public.gmane.org>
Cc: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Gavin Shan <gwshan-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, linuxppc-dev <linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org>, "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Bjorn Helgaas <bhelgaas-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
List-Id: devicetree@vger.kernel.org

On Thu, 2015-05-14 at 10:34 +0300, Pantelis Antoniou wrote:

> >> What you describe is inserting a bunch of properties and nodes und=
er
> >> a slot=E2=80=99s device node. Reverting the overlay removes them a=
ll just fine.
> >=20
> > Except that still doesn't work for boot time :-)
> >=20
> > So I would have to do a special case on unplug:
> >=20
> > 	if (slot->dt_is_overlay) /* set to false at boot */
> > 		remove_subtree_myself();
> > 	else
> > 		undo_overlay(slot->overlay);
> >=20
>=20
> OK, in that case you do require removal. But in any case it=E2=80=99s=
 the =E2=80=98negative=E2=80=99
> of an already applied one, either at boot time or not.

Sort-of, unless we have a way in the overlay to simply specify node
removal statements so we don't have to explicitly remove all properties
(or even all children).

> Modifying the overlay code to apply a =E2=80=98negative=E2=80=99 prop=
erty should do the trick.
>=20
> Is that correct?

I would do negatives node and let Linux imply the properties (or even
children).

But yes, that would probably do.

 .../...

> I will probably need that generation count myself for my PCI use case=
=2E
>=20
> > However that requires supporting removal of nodes/properties. So I'=
m
> > tempted to keep that feature on the back burner and go with an ad-h=
oc
> > interface for PCI for now.
> >=20
>=20
> I see. Bonne chance :)

Merci :)

Cheers,
Ben.


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