Messages in this thread |  | | From | Rob Herring <> | Date | Wed, 4 Apr 2018 19:55:36 -0500 | Subject | Re: [PATCH v7 2/5] of: change overlay apply input data from unflattened to FDT |
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On Wed, Apr 4, 2018 at 5:35 PM, Jan Kiszka <jan.kiszka@web.de> wrote: > Hi Frank, > > On 2018-03-04 01:17, frowand.list@gmail.com wrote: >> From: Frank Rowand <frank.rowand@sony.com> >> >> Move duplicating and unflattening of an overlay flattened devicetree >> (FDT) into the overlay application code. To accomplish this, >> of_overlay_apply() is replaced by of_overlay_fdt_apply(). >> >> The copy of the FDT (aka "duplicate FDT") now belongs to devicetree >> code, which is thus responsible for freeing the duplicate FDT. The >> caller of of_overlay_fdt_apply() remains responsible for freeing the >> original FDT. >> >> The unflattened devicetree now belongs to devicetree code, which is >> thus responsible for freeing the unflattened devicetree. >> >> These ownership changes prevent early freeing of the duplicated FDT >> or the unflattened devicetree, which could result in use after free >> errors. >> >> of_overlay_fdt_apply() is a private function for the anticipated >> overlay loader. > > We are using of_fdt_unflatten_tree + of_overlay_apply in the > (out-of-tree) Jailhouse loader driver in order to register a virtual > device during hypervisor activation with Linux. The DT overlay is > created from a a template but modified prior to application to account > for runtime-specific parameters. See [1] for the current implementation. > > I'm now wondering how to model that scenario best with the new API. > Given that the loader lost ownership of the unflattened tree but the > modification API exist only for the that DT state, I'm not yet seeing a > clear solution. Should we apply the template in disabled form (status = > "disabled"), modify it, and then activate it while it is already applied?
No. I don't think that will work.
The of_overlay_apply() function is still there, but static. We can export it again if the need arises.
Another option is there is a notifier callback OF_OVERLAY_PRE_APPLY, but I'm not sure we want to make that be the normal interface to make modifications.
Rob
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