[PATCH] FIT: support kernel images with type = "kernel_noload"

[Ahmad Fatoum]

U-Boot interprets "kernel_noload" to mean that the load and entry
addresses shall be ignored[1] and that the kernel image should be executed
in-place, unless compressed[2]. The entry and load addresses are still
mandatory and need to be initialized to some dummy value according to
spec[3].

barebox, which is unaware of any special semantics for the kernel_noload
type, would thus try to place a kernel_noload image at the dummy load
address specified and fail if that's not possible. Fix this by treating
type = "kernel_noload" as if load and entry properties were omitted,
in which case barebox falls back to find a suitable memory region at
runtime.

This change is motivated by the Linux kernel series adding FIT as
additional Kbuild target for ARM64[4]. With the change here, it's possible
to consume these FIT images in barebox as well.

[1]: U-Boot commit b9b50e89d317 ("image: Implement IH_TYPE_KERNEL_NOLOAD")
[2]: https://patchwork.ozlabs.org/project/uboot/list/?series=382849&state=*
[3]: https://github.com/open-source-firmware/flat-image-tree/releases/download/v0.8/fit-specification-v0.8.pdf
[4]: https://lore.kernel.org/linux-arm-kernel/20231129172200.430674-1-sjg@chromium.org/T/#meb5bda548de8d8d403c67ee90f639923c8a182fa

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 common/image-fit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/common/image-fit.c b/common/image-fit.c
index 0352dc5cbd0c..5ef5013bd41d 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -545,6 +545,7 @@ int fit_get_image_address(struct fit_handle *handle, void *configuration,
 {
 	struct device_node *image;
 	const char *unit = name;
+	const char *type;
 	int ret;
 
 	if (!address || !property || !name)
@@ -554,6 +555,11 @@ int fit_get_image_address(struct fit_handle *handle, void *configuration,
 	if (ret)
 		return ret;
 
+	/* Treat type = "kernel_noload" as if entry/load address is missing */
+	ret = of_property_read_string(image, "type", &type);
+	if (!ret && !strcmp(type, "kernel_noload"))
+	    return -ENOENT;
+
 	ret = fit_get_address(image, property, address);
 
 	return ret;
-- 
2.39.2