Hello David,
On Mon, Feb 26, 2024 at 04:53:53PM +1100, David Gibson wrote:
> On Sun, Feb 25, 2024 at 06:54:23PM +0100, Uwe Kleine-König wrote:
> > A phandle in an overlay is not supposed to overwrite a phandle that
> > already exists in the base dtb as this breaks references to the
> > respective node in the base.
> >
> > So add another iteration over the fdto that checks for such overwrites
> > and fixes the fdto phandle's value to match the fdt's.
> >
> > A test is added that checks that newly added phandles and existing
> > phandles work as expected.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> > ---
> > Hello,
> >
> > here comes the next iteration of the patch that fixes overlay
> > application to not overwrite existing phandles.
> >
> > It is rebased to current main branch. The changes since v2 are:
> >
> > - Add documentation
> > - Apply the simplification from 24f60011fd43 ("libfdt: Simplify
> > adjustment of values for local fixups") in the functions added here.
> > - Rename functions using shorter and better names
> > - Changed the test device trees to yield a hole in the phandle space
> > - Checked each phandle value not being overwritten separately
> >
> > Note I didn't switch the order of overlay_prevent_phandle_overwrite() and
> > overlay_fixup_phandles() because the overlay's phandles must be resolved
> > before I can do the recursion needed in
> > overlay_prevent_phandle_overwrite().
>
> I'm not following what you mean here. IIUC, conflicts of the sort
> you're handling can only arise when the overlay describes a phandle
> for the target node of the reference - and therefore that target is in
> the overlay. In that case all references to it in the overlay should
> be encoded in __local_fixups__ rather than __fixups__. __fixups__, in
> contrast describes references to nodes that aren't in the overlay, and
> so can't be filled in - even with a tentative value - until the
> overlay is applied.
>
> So, I'm not seeing how fixing these conflicts depends on resolution of
> those "external" fixups, rather than just the "local" fixups. Am I
> missing something?
yupp, look at the overlay dts I added in tests/. It has
&node_a {
value = <32>;
};
which is translated to:
fragment@1 {
target = <0xffffffff>;
__overlay__ {
value = <0x00000020>;
};
};
...
__fixups__ {
node_a = ..., "/fragment@1:target:0"
};
Before I can recurse over fragment@1 and the matching base dtb node to
check for phandle conflicts, I need /fragment@1:target resolved;
otherwise I don't know where to look in the base dtb.
So if I switch the order, fdtoverlay reports
Failed to apply 'overlay_overlay_phandle.test.dtb': FDT_ERR_BADPHANDLE
in make check.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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