// SPDX-License-Identifier: GPL-2.0

#define pr_fmt(fmt) "[rootfs] " fmt

#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/root_dev.h>
#include "avm_mtd_helper.h"

static const char *rootfs_names[] = { "rootfs_ram", "rootfs", "filesystem" };

static void rootfs_add_notifier(struct mtd_info *mtd)
{
	static int found_rootfs_idx = -1;

	int i;
	int match = 0;

	if (!mtd->name)
		return;

	for (i = 0; !match && i < ARRAY_SIZE(rootfs_names); i++)
		if (!strcmp(rootfs_names[i], mtd->name))
			match = 1;

	if (!match && strstarts(mtd->name, "filesystem")) {
		u8 expected_fs, fs;

		expected_fs = prom_get_linux_fs();

		if (!kstrtou8(mtd->name + strlen("filesystem"), 10, &fs)) {
			pr_debug("mtd %s: fs=%d expected=%d\n", mtd->name, fs,
				 expected_fs);

			match = (fs == expected_fs);
			i = ARRAY_SIZE(rootfs_names) + 1;
		} else
			pr_warn("mtd %s does not end with an valid number\n",
				mtd->name);
	}

	if (!match) {
		pr_debug("mtd %s: not a rootfs\n", mtd->name);
		return;
	}

	if (found_rootfs_idx != -1 && found_rootfs_idx < i) {
		pr_debug(
			"mtd %s: lower priority than existing root dev, ignoring\n.",
			mtd->name);
		return;
	}

	pr_notice("use mtd%d (%s) as root\n", mtd->index, mtd->name);

	found_rootfs_idx = i;

	/*
	 * Setting ROOT_DEV only works when CONFIG_BLOCK and CONFIG_MTD_BLOCK
	 * is enabled. (The latter has the former as dependency).
	 *
	 * For some reason the old code had a fallback to emulate a "root="
	 * cmdline option. CONFIG_MTD_BLOCK is set on all qca products, but to
	 * avoid surprises we complain here if needed.
	 */
	BUILD_BUG_ON(!IS_ENABLED(CONFIG_MTD_BLOCK));

	ROOT_DEV = MKDEV(MTD_BLOCK_MAJOR, mtd->index);
}

static void rootfs_rm_notifier(struct mtd_info *mtd)
{
}

struct mtd_notifier avm_mtd_rootfs_notifier = {
	.add = rootfs_add_notifier,
	.remove = rootfs_rm_notifier,
};