boot: Add UCLASS support for extension boards

Introduce UCLASS-based extension board support to enable more
standardized and automatic loading of extension board device tree
overlays in preparation for integration with bootstd and pxe_utils.

Several #if CONFIG_IS_ENABLED are used in cmd/extension_board.c to ease the
development but don't worry they are removed later in the series.

Signed-off-by: Kory Maincent (TI.com) <[email protected]>
Reviewed-by: Simon Glass <[email protected]>

3 files changed, 156 insertions, 0 deletions

diff --git a/boot/Kconfig b/boot/Kconfig
index a75f6b641ed..08d666d4b93 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -1910,6 +1910,10 @@ config SUPPORT_EXTENSION_SCAN
 	select OF_LIBFDT_OVERLAY
         bool
 
+config SUPPORT_DM_EXTENSION_SCAN
+	select OF_LIBFDT_OVERLAY
+        bool
+
 config USE_BOOTARGS
 	bool "Enable boot arguments"
 	help
diff --git a/boot/Makefile b/boot/Makefile
index f60d13130b1..aa26070fbb8 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_CMD_BOOTM) += bootm.o bootm_os.o
 obj-$(CONFIG_CMD_BOOTZ) += bootm.o bootm_os.o
 obj-$(CONFIG_CMD_BOOTI) += bootm.o bootm_os.o
 obj-$(CONFIG_SUPPORT_EXTENSION_SCAN) += extension.o
+obj-$(CONFIG_SUPPORT_DM_EXTENSION_SCAN) += extension-uclass.o
 
 obj-$(CONFIG_PXE_UTILS) += pxe_utils.o
 
diff --git a/boot/extension-uclass.c b/boot/extension-uclass.c
new file mode 100644
index 00000000000..914971215af
--- /dev/null
+++ b/boot/extension-uclass.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2025 Köry Maincent <[email protected]>
+ */
+
+#include <alist.h>
+#include <command.h>
+#include <env.h>
+#include <extension_board.h>
+#include <fdt_support.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <dm/device-internal.h>
+#include <dm/lists.h>
+#include <dm/uclass.h>
+
+struct alist *dm_extension_get_list(void)
+{
+	struct udevice *dev;
+
+	if (uclass_first_device_err(UCLASS_EXTENSION, &dev))
+		return NULL;
+
+	return dev_get_priv(dev);
+}
+
+int dm_extension_probe(struct udevice *dev)
+{
+	struct alist *extension_list = dev_get_priv(dev);
+
+	alist_init_struct(extension_list, struct extension);
+	return 0;
+}
+
+int dm_extension_remove(struct udevice *dev)
+{
+	struct alist *extension_list = dev_get_priv(dev);
+
+	alist_uninit(extension_list);
+	return 0;
+}
+
+int dm_extension_scan(void)
+{
+	struct alist *extension_list = dm_extension_get_list();
+	const struct extension_ops *ops;
+	struct udevice *dev;
+	int ret;
+
+	ret = uclass_first_device_err(UCLASS_EXTENSION, &dev);
+	if (ret)
+		return ret;
+
+	if (!extension_list)
+		return -ENODEV;
+
+	ops = extension_get_ops(dev);
+	alist_empty(extension_list);
+	return ops->scan(dev, extension_list);
+}
+
+static int _extension_apply(const struct extension *extension)
+{
+	ulong extrasize, overlay_addr;
+	struct fdt_header *blob;
+	char *overlay_cmd;
+	int ret;
+
+	if (!working_fdt) {
+		printf("No FDT memory address configured. Please configure\n"
+		       "the FDT address via \"fdt addr <address>\" command.\n");
+		return -EINVAL;
+	}
+
+	overlay_cmd = env_get("extension_overlay_cmd");
+	if (!overlay_cmd) {
+		printf("Environment extension_overlay_cmd is missing\n");
+		return -EINVAL;
+	}
+
+	overlay_addr = env_get_hex("extension_overlay_addr", 0);
+	if (!overlay_addr) {
+		printf("Environment extension_overlay_addr is missing\n");
+		return -EINVAL;
+	}
+
+	env_set("extension_overlay_name", extension->overlay);
+	ret = run_command(overlay_cmd, 0);
+	if (ret)
+		return ret;
+
+	extrasize = env_get_hex("filesize", 0);
+	if (!extrasize)
+		return -EINVAL;
+
+	fdt_shrink_to_minimum(working_fdt, extrasize);
+
+	blob = map_sysmem(overlay_addr, 0);
+	if (!fdt_valid(&blob)) {
+		printf("Invalid overlay devicetree %s\n", extension->overlay);
+		return -EINVAL;
+	}
+
+	/* Apply method prints messages on error */
+	ret = fdt_overlay_apply_verbose(working_fdt, blob);
+	if (ret)
+		printf("Failed to apply overlay %s\n", extension->overlay);
+
+	return ret;
+}
+
+int dm_extension_apply(int extension_num)
+{
+	struct alist *extension_list = dm_extension_get_list();
+	const struct extension *extension;
+
+	if (!extension_list)
+		return -ENOENT;
+
+	extension = alist_get(extension_list, extension_num,
+			      struct extension);
+	if (!extension) {
+		printf("Wrong extension number\n");
+		return -EINVAL;
+	}
+
+	return _extension_apply(extension);
+}
+
+int dm_extension_apply_all(void)
+{
+	struct alist *extension_list = dm_extension_get_list();
+	const struct extension *extension;
+	int ret;
+
+	if (!extension_list)
+		return -ENOENT;
+
+	alist_for_each(extension, extension_list) {
+		ret = _extension_apply(extension);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+UCLASS_DRIVER(extension) = {
+	.name	= "extension",
+	.id	= UCLASS_EXTENSION,
+};