--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/crc32.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+enum u_boot_env_format {
+ U_BOOT_FORMAT_SINGLE,
+ U_BOOT_FORMAT_REDUNDANT,
+};
+
+struct u_boot_env {
+ struct device *dev;
+ enum u_boot_env_format format;
+
+ struct mtd_info *mtd;
+
+ /* Cells */
+ struct nvmem_cell_info *cells;
+ int ncells;
+};
+
+struct u_boot_env_image_single {
+ __le32 crc32;
+ uint8_t data[];
+} __packed;
+
+struct u_boot_env_image_redundant {
+ __le32 crc32;
+ u8 mark;
+ uint8_t data[];
+} __packed;
+
+static int u_boot_env_read(void *context, unsigned int offset, void *val,
+ size_t bytes)
+{
+ struct u_boot_env *priv = context;
+ struct device *dev = priv->dev;
+ size_t bytes_read;
+ int err;
+
+ err = mtd_read(priv->mtd, offset, bytes, &bytes_read, val);
+ if (err && !mtd_is_bitflip(err)) {
+ dev_err(dev, "Failed to read from mtd: %d\n", err);
+ return err;
+ }
+
+ if (bytes_read != bytes) {
+ dev_err(dev, "Failed to read %zu bytes\n", bytes);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int u_boot_env_add_cells(struct u_boot_env *priv, uint8_t *buf,
+ size_t data_offset, size_t data_len)
+{
+ struct device *dev = priv->dev;
+ char *data = buf + data_offset;
+ char *var, *value, *eq;
+ int idx;
+
+ priv->ncells = 0;
+ for (var = data; var < data + data_len && *var; var += strlen(var) + 1)
+ priv->ncells++;
+
+ priv->cells = devm_kcalloc(dev, priv->ncells, sizeof(*priv->cells), GFP_KERNEL);
+ if (!priv->cells)
+ return -ENOMEM;
+
+ for (var = data, idx = 0;
+ var < data + data_len && *var;
+ var = value + strlen(value) + 1, idx++) {
+ eq = strchr(var, '=');
+ if (!eq)
+ break;
+ *eq = '\0';
+ value = eq + 1;
+
+ priv->cells[idx].name = devm_kstrdup(dev, var, GFP_KERNEL);
+ if (!priv->cells[idx].name)
+ return -ENOMEM;
+ priv->cells[idx].offset = data_offset + value - data;
+ priv->cells[idx].bytes = strlen(value);
+ }
+
+ if (WARN_ON(idx != priv->ncells))
+ priv->ncells = idx;
+
+ return 0;
+}
+
+static int u_boot_env_parse(struct u_boot_env *priv)
+{
+ struct device *dev = priv->dev;
+ size_t crc32_data_offset;
+ size_t crc32_data_len;
+ size_t crc32_offset;
+ size_t data_offset;
+ size_t data_len;
+ uint32_t crc32;
+ uint32_t calc;
+ size_t bytes;
+ uint8_t *buf;
+ int err;
+
+ buf = kcalloc(1, priv->mtd->size, GFP_KERNEL);
+ if (!buf) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+
+ err = mtd_read(priv->mtd, 0, priv->mtd->size, &bytes, buf);
+ if ((err && !mtd_is_bitflip(err)) || bytes != priv->mtd->size) {
+ dev_err(dev, "Failed to read from mtd: %d\n", err);
+ goto err_kfree;
+ }
+
+ switch (priv->format) {
+ case U_BOOT_FORMAT_SINGLE:
+ crc32_offset = offsetof(struct u_boot_env_image_single, crc32);
+ crc32_data_offset = offsetof(struct u_boot_env_image_single, data);
+ data_offset = offsetof(struct u_boot_env_image_single, data);
+ break;
+ case U_BOOT_FORMAT_REDUNDANT:
+ crc32_offset = offsetof(struct u_boot_env_image_redundant, crc32);
+ crc32_data_offset = offsetof(struct u_boot_env_image_redundant, mark);
+ data_offset = offsetof(struct u_boot_env_image_redundant, data);
+ break;
+ }
+ crc32 = le32_to_cpu(*(uint32_t *)(buf + crc32_offset));
+ crc32_data_len = priv->mtd->size - crc32_data_offset;
+ data_len = priv->mtd->size - data_offset;
+
+ calc = crc32(~0, buf + crc32_data_offset, crc32_data_len) ^ ~0L;
+ if (calc != crc32) {
+ dev_err(dev, "Invalid calculated CRC32: 0x%08x (expected: 0x%08x)\n", calc, crc32);
+ err = -EINVAL;
+ goto err_kfree;
+ }
+
+ buf[priv->mtd->size - 1] = '\0';
+ err = u_boot_env_add_cells(priv, buf, data_offset, data_len);
+ if (err)
+ dev_err(dev, "Failed to add cells: %d\n", err);
+
+err_kfree:
+ kfree(buf);
+err_out:
+ return err;
+}
+
+static int u_boot_env_probe(struct platform_device *pdev)
+{
+ struct nvmem_config config = {
+ .name = "u-boot-env",
+ .reg_read = u_boot_env_read,
+ };
+ struct device *dev = &pdev->dev;
+ struct device_node *np = dev->of_node;
+ struct u_boot_env *priv;
+ int err;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+ priv->dev = dev;
+
+ priv->format = (uintptr_t)of_device_get_match_data(dev);
+
+ priv->mtd = of_get_mtd_device_by_node(np);
+ if (IS_ERR(priv->mtd)) {
+ dev_err_probe(dev, PTR_ERR(priv->mtd), "Failed to get %pOF MTD\n", np);
+ return PTR_ERR(priv->mtd);
+ }
+
+ err = u_boot_env_parse(priv);
+ if (err)
+ return err;
+
+ config.dev = dev;
+ config.cells = priv->cells;
+ config.ncells = priv->ncells;
+ config.priv = priv;
+ config.size = priv->mtd->size;
+
+ return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
+}
+
+static const struct of_device_id u_boot_env_of_match_table[] = {
+ { .compatible = "u-boot,env", .data = (void *)U_BOOT_FORMAT_SINGLE, },
+ { .compatible = "u-boot,env-redundant-bool", .data = (void *)U_BOOT_FORMAT_REDUNDANT, },
+ { .compatible = "u-boot,env-redundant-count", .data = (void *)U_BOOT_FORMAT_REDUNDANT, },
+ {},
+};
+
+static struct platform_driver u_boot_env_driver = {
+ .probe = u_boot_env_probe,
+ .driver = {
+ .name = "u_boot_env",
+ .of_match_table = u_boot_env_of_match_table,
+ },
+};
+module_platform_driver(u_boot_env_driver);
+
+MODULE_AUTHOR("Rafał Miłecki");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(of, u_boot_env_of_match_table);
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