Hello David,
On Thu, Feb 22, 2024 at 05:32:10PM +1100, David Gibson wrote:
> On Fri, Feb 16, 2024 at 07:19:20PM +0100, Uwe Kleine-König wrote:
> > [...]
> > diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
> > index 5c0c3981b89d..914acc5b14a6 100644
> > --- a/libfdt/fdt_overlay.c
> > +++ b/libfdt/fdt_overlay.c
> > @@ -520,6 +520,228 @@ static int overlay_fixup_phandles(void *fdt, void *fdto)
> > return 0;
> > }
> >
>
> All of these new functions could do with descriptive comments saying
> what they do (see the existing code for examples).
Yeah, I was lazy. I didn't expect this patch to go in without comments
and avoided investing time documenting functions that maybe will change
in the course of the review-resend loop. :-)
> > [...]
> > +static int overlay_update_node_conflicting_references(void *fdto, int tree_node,
> > + int fixup_node,
> > + uint32_t fdt_phandle,
> > + uint32_t fdto_phandle)
> > +{
> > + int fixup_prop;
> > + int fixup_child;
> > + int ret;
> > +
> > + fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) {
> > +
>
> Extraneous blank line.
>
> > + const fdt32_t *fixup_val;
> > + const char *tree_val;
>
> libfdt style is to use tab indents, looks like most of this block has
> space indents instead.
Huh, I'm surprised about myself that I didn't notice this alone.
> > +
> > + /*
> > + * phandles to fixup can be unaligned.
> > + *
> > + * Use a memcpy for the architectures that do
> > + * not support unaligned accesses.
> > + */
> > + memcpy(&adj_val, tree_val + poffset, sizeof(adj_val));
>
> And here you can use fdt32_ld() which has unaligned access handling
> built in.
I copied this from somewhere, so I guess there is some potential for
improvement in existing code. Will take a look.
> > [...]
> > +
> > +static int overlay_prevent_phandle_overwrite_node(void *fdt, int fdtnode,
> > + void *fdto, int fdtonode)
>
> Maybe "overlay_resolve_phandle_conflict()" for a slightly shorter
> function name.
Sounds good, wasn't too lucky with
overlay_prevent_phandle_overwrite_node() either.
> > +{
> > + uint32_t fdt_phandle, fdto_phandle;
> > + int fdtochild;
> > +
> > + fdt_phandle = fdt_get_phandle(fdt, fdtnode);
> > + fdto_phandle = fdt_get_phandle(fdto, fdtonode);
> > +
> > + if (fdt_phandle && fdto_phandle) {
> > + int ret;
> > +
> > + ret = overlay_adjust_local_conflicting_phandle(fdto,
> > + fdt_phandle,
> > + fdto_phandle);
> > + if (ret)
> > + return ret;
>
> So while, as you've seen, there can be conflicting phandles between
> the fdt and the fdto, within the fdto a particular phandle should only
> appear on a single node. If a phandle is duplicated across nodes
> witin a single fdto, you have bigger problems. Therefore, having
> found a conflict, you're already found the only place you need to
> change the phandle property itself - you don't need to scan the full
> fdto again.
>
> So I believe you can replace the above call with just setting the
> phandle property on fdtonode.
Oh right!
> > [...]
> > /**
> > * overlay_apply_node - Merges a node into the base device tree
> > * @fdt: Base Device Tree blob
> > @@ -824,18 +1046,26 @@ int fdt_overlay_apply(void *fdt, void *fdto)
> > if (ret)
> > goto err;
> >
> > + /* Increase all phandles in the fdto by delta */
> > ret = overlay_adjust_local_phandles(fdto, delta);
> > if (ret)
> > goto err;
> >
> > + /* Adapt the phandle values in fdto to the above increase */
> > ret = overlay_update_local_references(fdto, delta);
> > if (ret)
> > goto err;
> >
> > + /* Update fdto's phandles using symbols from fdt */
> > ret = overlay_fixup_phandles(fdt, fdto);
> > if (ret)
> > goto err;
> >
> > + /* Don't overwrite phandles in fdt */
> > + ret = overlay_prevent_phandle_overwrite(fdt, fdto);
> > + if (ret)
> > + goto err;
>
> I think this should go above overlay_fixup_phandles(), so that we're
> completing all the __local_fixups__ based adjustments before going to
> the __fixups__ based adjustments.
This is only to please the reader, right? Or is there a corner case I
failed to see?
The feedback I removed in this mail I agree with. Expect a v3 soon.
Thanks for your time to review my patch,
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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