[PATCH v5 07/11] of: overlay: add FIT image overlay support
Sascha Hauer
s.hauer at pengutronix.de
Mon Aug 18 23:38:07 PDT 2025
On Mon, Aug 18, 2025 at 07:26:15PM +0200, Marco Felsch wrote:
> This adds the support to load devicetree overlays from a FIT image.
> There are a few options to handle FIT overlays since the FIT overlay
> spec is not very strict.
>
> This implements the most configurable case where each overlay does have
> its own config node (including the optional signature).
>
> - The "pattern" filter matches the config-node names (the node names
> below the configurations node), not the overlay image names (the node
> names below the images node).
>
> - The "compatible" filter check doesn't differ from the file based overlay
> handling.
>
> Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> ---
> Documentation/user/devicetree.rst | 19 +++---
> drivers/of/overlay.c | 126 +++++++++++++++++++++++++++++++++++---
> 2 files changed, 128 insertions(+), 17 deletions(-)
>
> diff --git a/Documentation/user/devicetree.rst b/Documentation/user/devicetree.rst
> index 30a15a8865c154f8afe23d641da10d0afa84423b..644fb551adcf913ca9ed2ab3f1d5fbe7c367bdf6 100644
> --- a/Documentation/user/devicetree.rst
> +++ b/Documentation/user/devicetree.rst
> @@ -109,20 +109,23 @@ Overlays can be applied to the kernel device tree before it is handed over to
> the kernel. The behaviour is controlled by different variables:
>
> ``global.of.overlay.path``
> - Overlays are read from this directory. barebox will try to apply all overlays
> - found here if not limited by one of the other variables below. When the path
> - given here is an absolute path it is used as is. A relative path is relative
> - to ``/`` or relative to the rootfs when using bootloader spec.
> + Overlays are read from this path. The path can either be a directory which
> + contains the overlays or an absolute path to a FIT-image. barebox will try to
is "absolute path" correct here?
Before it was either an absolute path or a path relative to the
rootfs...
> + apply all overlays found if not limited by one of the other variables below.
> + When the path given here is an absolute path it is used as is. A relative
> + path is relative to ``/`` or relative to the rootfs when using bootloader
> + spec.
...and this still seems to be the case.
Isn't this true for overlays in FIT images as weel? If yes I suggest to
just remove the "absolute".
> ``global.of.overlay.compatible``
> This is a space separated list of compatibles. Only overlays matching one of
> these compatibles will be applied. When this list is empty then all overlays
> will be applied. Overlays that don't have a compatible are considered being
> always compatible.
> ``global.of.overlay.pattern``
> - This is a space separated list of file patterns. An overlay is only applied
> - when its filename matches one of the patterns. The patterns can contain
> - ``*`` and ``?`` as wildcards. The default is ``*`` which means all files are
> - applied.
> + This is a space separated list of file patterns or FIT-image config-node name
> + patterns. An overlay is only applied when its filename or FIT-image
> + config-node name matches one of the patterns. The patterns can contain ``*``
> + and ``?`` as wildcards. The default is ``*`` which means all files or FIT-Image
> + config-nodes are applied.
> ``global.of.overlay.filter``
> This is a space separated list of filters to apply. There are two generic filters:
> ``pattern`` matches ``global.of.overlay.pattern`` above, ``compatible`` matches
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index f02a12d44f0d53db3fb7bb065461c0ef193d0ab3..6defd6fa6908ff2b2fd00d161464af37ac17e040 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -8,10 +8,12 @@
> */
> #define pr_fmt(fmt) "of_overlay: " fmt
>
> +#include <bootm.h>
> #include <common.h>
> #include <of.h>
> #include <errno.h>
> #include <globalvar.h>
> +#include <image-fit.h>
> #include <magicvar.h>
> #include <string.h>
> #include <libfile.h>
> @@ -463,8 +465,100 @@ static int of_overlay_apply_dir(struct device_node *root, const char *dirname,
> return ret;
> }
>
> +static int of_overlay_apply_fit(struct device_node *root, struct fit_handle *fit,
> + struct device_node *config)
> +{
> + const char *name = config->name;
> + struct device_node *overlay;
> + unsigned long ovl_sz;
> + const void *ovl;
> + int ret;
> +
> + if (!of_overlay_matches_filter(name, NULL))
> + return 0;
Can we have a
pr_debug("FIT config \"%s\" doesn't match filter \"%s\"\n",
name, of_overlay_filter);
Here?
> +
> + ret = fit_open_image(fit, config, "fdt", &ovl, &ovl_sz);
> + if (ret)
> + return ret;
> +
> + overlay = of_unflatten_dtb(ovl, ovl_sz);
if (IS_ERR(overlay))
...
> +
> + if (!of_overlay_matches_filter(NULL, overlay)) {
> + ret = 0;
> + goto out;
> + }
I think a pr_debug printing the reason would be appropriate here as
well.
> +
> + ret = of_overlay_apply_tree(root, overlay);
> + if (ret == -ENODEV)
> + pr_debug("Not applied %s (not compatible)\n", name);
> + else if (ret)
> + pr_err("Cannot apply %s: %s\n", name, strerror(-ret));
> + else
> + pr_info("Applied %s\n", name);
> +
> +out:
> + of_delete_node(overlay);
> +
> + return ret;
> +}
> +
> +static bool of_overlay_valid_config(struct fit_handle *fit,
> + struct device_node *config)
> +{
> + /*
> + * Either kernel or firmware is marked as mandatory by U-Boot
> + * (doc/usage/fit/source_file_format.rst) except for overlays
> + * (doc/usage/fit/overlay-fdt-boot.rst). Therefore we need to ensure
> + * that only "fdt" config nodes are recognized as overlay config node.
> + */
> + if (!fit_has_image(fit, config, "fdt") ||
> + fit_has_image(fit, config, "kernel") ||
> + fit_has_image(fit, config, "firmware"))
> + return false;
> +
> + return true;
> +}
> +
> +static int of_overlay_global_fixup_fit(struct device_node *root,
> + const char *fit_path, loff_t fit_size)
> +{
> + enum bootm_verify verify = bootm_get_verify_mode();
> + struct device_node *conf_node;
> + struct fit_handle *fit;
> + int ret;
> +
> + if (!IS_ENABLED(CONFIG_FITIMAGE)) {
> + pr_err("FIT based overlay handling requested while CONFIG_FITIMAGE=n\n");
> + return -EINVAL;
> + }
> +
> + fit = fit_open(fit_path, 0, verify, fit_size);
> + if (IS_ERR(fit)) {
> + pr_err("Loading FIT image %s failed with: %pe\n", fit_path, fit);
> + return PTR_ERR(fit);
> + }
> +
> + for_each_child_of_node(fit->configurations, conf_node) {
> + if (!of_overlay_valid_config(fit, conf_node))
> + continue;
> +
> + ret = fit_config_verify_signature(fit, conf_node);
> + if (ret)
> + goto out;
> +
> + ret = of_overlay_apply_fit(root, fit, conf_node);
> + if (ret)
> + goto out;
> + }
> +
> +out:
> + fit_close(fit);
> + return ret;
> +}
> +
> static int of_overlay_global_fixup(struct device_node *root, void *data)
> {
> + struct stat s;
> char *dir;
> int ret;
>
> @@ -476,10 +570,24 @@ static int of_overlay_global_fixup(struct device_node *root, void *data)
> else
> dir = concat_path_file(of_overlay_basedir, of_overlay_path);
>
> - ret = of_overlay_apply_dir(root, dir, true);
>
> - free(dir);
> + if (stat(dir, &s)) {
> + pr_err("Cannot stat global.of.overlay.path (%s): %s\n",
> + dir, strerror(errno));
Use %m which prints strerror(errno) directly.
Sascha
--
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