[PATCH v4 07/11] of: overlay: add FIT image overlay support

[Sascha Hauer]

On Tue, Jul 29, 2025 at 05:34:32PM +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              | 132 +++++++++++++++++++++++++++++++++++---
>  2 files changed, 134 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index f02a12d44f0d53db3fb7bb065461c0ef193d0ab3..604ce0998cd8044cca59c40e65f4e9b95bec6112 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -8,10 +8,13 @@
>   */
>  #define pr_fmt(fmt) "of_overlay: " fmt
>  
> +#include <bootm.h>
>  #include <common.h>
>  #include <of.h>
>  #include <errno.h>
> +#include <filetype.h>
>  #include <globalvar.h>
> +#include <image-fit.h>
>  #include <magicvar.h>
>  #include <string.h>
>  #include <libfile.h>
> @@ -463,8 +466,99 @@ 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;
> +
> +	ret = fit_open_image(fit, config, "fdt", &ovl, &ovl_sz);
> +	if (ret)
> +		return ret;
> +
> +	overlay = of_unflatten_dtb(ovl, ovl_sz);
> +
> +	if (!of_overlay_matches_filter(NULL, overlay)) {
> +		ret = 0;
> +		goto out;
> +	}
> +
> +	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))
> +		return 0;

The comments in https://lore.barebox.org/barebox/ZpT3h0o089tae2WS@pengutronix.de/
do not seem to be addressed here.

Sascha

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