From: David Gibson <david@gibson.dropbear.id.au>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Yves-Alexis Perez <corsac@debian.org>,
devicetree-compiler@vger.kernel.org, entwicklung@pengutronix.de
Subject: Re: [PATCH v2] libfdt: overlay: ensure that existing phandles are not overwritten
Date: Thu, 22 Feb 2024 17:33:00 +1100 [thread overview]
Message-ID: <ZdbqnDY2k6sU0JRy@zatzit> (raw)
In-Reply-To: <fgyaporsv6l5jqtseabnhzykf4xlfwrxmnpokqanxoyfkzkkfi@kkdu7cfdkgnt>
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On Fri, Feb 16, 2024 at 10:06:37PM +0100, Uwe Kleine-König wrote:
> Hello,
>
> On Fri, Feb 16, 2024 at 07:19:20PM +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@pengutronix.de>
>
> After sending the patch out I had a nice idea for an optimisation here.
> It doesn't make the process faster, but improves the result.
>
> If phandle with the (shifted) value 17 is changed to 5, there is no
> phandle with the value 17 in the end. So while iterating over the fdto
> to replace all phandles with value 17 by 5 all values > 17 can be
> reduced by one. This way the phandle allocation in the resulting dtb is
> continuous if both inputs have continuous numbers.
Honestly, I don't think the marginal advantage of improving the
chances of contiguous phandles is worth the extra complexity.
>
> This can be implemented by the patch below on top of the patch I'm
> replying to.
>
> Best regards
> Uwe
>
> diff --git a/libfdt/fdt_overlay.c b/libfdt/fdt_overlay.c
> index 914acc5b14a6..bfdba50dee50 100644
> --- a/libfdt/fdt_overlay.c
> +++ b/libfdt/fdt_overlay.c
> @@ -529,15 +529,25 @@ static int overlay_adjust_node_conflicting_phandle(void *fdto, int node,
> int child;
>
> php = fdt_getprop(fdto, node, "phandle", &len);
> - if (php && len == sizeof(*php) && fdt32_to_cpu(*php) == fdto_phandle) {
> - ret = fdt_setprop_inplace_u32(fdto, node, "phandle", fdt_phandle);
> + if (php && len == sizeof(*php)) {
> + if (fdt32_to_cpu(*php) == fdto_phandle)
> + ret = fdt_setprop_inplace_u32(fdto, node, "phandle", fdt_phandle);
> + else if (fdt32_to_cpu(*php) > fdto_phandle)
> + ret = fdt_setprop_inplace_u32(fdto, node, "phandle", fdt32_to_cpu(*php) - 1);
> + else
> + ret = 0;
> if (ret)
> return ret;
> }
>
> php = fdt_getprop(fdto, node, "linux,phandle", &len);
> - if (php && len == sizeof(*php) && fdt32_to_cpu(*php) == fdto_phandle) {
> - ret = fdt_setprop_inplace_u32(fdto, node, "linux,phandle", fdt_phandle);
> + if (php && len == sizeof(*php)) {
> + if (fdt32_to_cpu(*php) == fdto_phandle)
> + ret = fdt_setprop_inplace_u32(fdto, node, "linux,phandle", fdt_phandle);
> + else if (fdt32_to_cpu(*php) > fdto_phandle)
> + ret = fdt_setprop_inplace_u32(fdto, node, "phandle", fdt32_to_cpu(*php) - 1);
> + else
> + ret = 0;
> if (ret)
> return ret;
> }
> @@ -609,23 +619,27 @@ static int overlay_update_node_conflicting_references(void *fdto, int tree_node,
> */
> memcpy(&adj_val, tree_val + poffset, sizeof(adj_val));
>
> - if (fdt32_to_cpu(adj_val) == fdto_phandle) {
> + if (fdt32_to_cpu(adj_val) < fdto_phandle)
> + continue;
>
> + if (fdt32_to_cpu(adj_val) == fdto_phandle)
> adj_val = cpu_to_fdt32(fdt_phandle);
> + else
> + adj_val = cpu_to_fdt32(fdt32_to_cpu(adj_val) - 1);
>
> - ret = fdt_setprop_inplace_namelen_partial(fdto,
> - tree_node,
> - name,
> - strlen(name),
> - poffset,
> - &adj_val,
> - sizeof(adj_val));
> - if (ret == -FDT_ERR_NOSPACE)
> - return -FDT_ERR_BADOVERLAY;
>
> - if (ret)
> - return ret;
> - }
> + ret = fdt_setprop_inplace_namelen_partial(fdto,
> + tree_node,
> + name,
> + strlen(name),
> + poffset,
> + &adj_val,
> + sizeof(adj_val));
> + if (ret == -FDT_ERR_NOSPACE)
> + return -FDT_ERR_BADOVERLAY;
> +
> + if (ret)
> + return ret;
> }
> }
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2024-02-22 6:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-16 18:19 [PATCH v2] libfdt: overlay: ensure that existing phandles are not overwritten Uwe Kleine-König
2024-02-16 21:06 ` Uwe Kleine-König
2024-02-22 6:33 ` David Gibson [this message]
2024-02-22 6:32 ` David Gibson
2024-02-22 7:22 ` Uwe Kleine-König
2024-02-22 9:02 ` David Gibson
2024-02-22 9:38 ` Uwe Kleine-König
2024-02-23 4:41 ` David Gibson
2024-02-23 7:53 ` Uwe Kleine-König
2024-02-23 8:15 ` David Gibson
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