1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2022 Rafał Miłecki <rafal@milecki.pl>
  4 */
  5
  6#include <linux/crc32.h>
  7#include <linux/mod_devicetable.h>
  8#include <linux/module.h>
  9#include <linux/mtd/mtd.h>
 10#include <linux/nvmem-consumer.h>
 11#include <linux/nvmem-provider.h>
 12#include <linux/of_device.h>
 13#include <linux/platform_device.h>
 14#include <linux/slab.h>
 15
 16enum u_boot_env_format {
 17	U_BOOT_FORMAT_SINGLE,
 18	U_BOOT_FORMAT_REDUNDANT,
 19	U_BOOT_FORMAT_BROADCOM,
 20};
 21
 22struct u_boot_env {
 23	struct device *dev;
 24	enum u_boot_env_format format;
 25
 26	struct mtd_info *mtd;
 27
 28	/* Cells */
 29	struct nvmem_cell_info *cells;
 30	int ncells;
 31};
 32
 33struct u_boot_env_image_single {
 34	__le32 crc32;
 35	uint8_t data[];
 36} __packed;
 37
 38struct u_boot_env_image_redundant {
 39	__le32 crc32;
 40	u8 mark;
 41	uint8_t data[];
 42} __packed;
 43
 44struct u_boot_env_image_broadcom {
 45	__le32 magic;
 46	__le32 len;
 47	__le32 crc32;
 48	uint8_t data[0];
 49} __packed;
 50
 51static int u_boot_env_read(void *context, unsigned int offset, void *val,
 52			   size_t bytes)
 53{
 54	struct u_boot_env *priv = context;
 55	struct device *dev = priv->dev;
 56	size_t bytes_read;
 57	int err;
 58
 59	err = mtd_read(priv->mtd, offset, bytes, &bytes_read, val);
 60	if (err && !mtd_is_bitflip(err)) {
 61		dev_err(dev, "Failed to read from mtd: %d\n", err);
 62		return err;
 63	}
 64
 65	if (bytes_read != bytes) {
 66		dev_err(dev, "Failed to read %zu bytes\n", bytes);
 67		return -EIO;
 68	}
 69
 70	return 0;
 71}
 72
 73static int u_boot_env_add_cells(struct u_boot_env *priv, uint8_t *buf,
 74				size_t data_offset, size_t data_len)
 75{
 76	struct device *dev = priv->dev;
 77	char *data = buf + data_offset;
 78	char *var, *value, *eq;
 79	int idx;
 80
 81	priv->ncells = 0;
 82	for (var = data; var < data + data_len && *var; var += strlen(var) + 1)
 83		priv->ncells++;
 84
 85	priv->cells = devm_kcalloc(dev, priv->ncells, sizeof(*priv->cells), GFP_KERNEL);
 86	if (!priv->cells)
 87		return -ENOMEM;
 88
 89	for (var = data, idx = 0;
 90	     var < data + data_len && *var;
 91	     var = value + strlen(value) + 1, idx++) {
 92		eq = strchr(var, '=');
 93		if (!eq)
 94			break;
 95		*eq = '\0';
 96		value = eq + 1;
 97
 98		priv->cells[idx].name = devm_kstrdup(dev, var, GFP_KERNEL);
 99		if (!priv->cells[idx].name)
100			return -ENOMEM;
101		priv->cells[idx].offset = data_offset + value - data;
102		priv->cells[idx].bytes = strlen(value);
103		priv->cells[idx].np = of_get_child_by_name(dev->of_node, priv->cells[idx].name);
104	}
105
106	if (WARN_ON(idx != priv->ncells))
107		priv->ncells = idx;
108
109	return 0;
110}
111
112static int u_boot_env_parse(struct u_boot_env *priv)
113{
114	struct device *dev = priv->dev;
115	size_t crc32_data_offset;
116	size_t crc32_data_len;
117	size_t crc32_offset;
118	size_t data_offset;
119	size_t data_len;
120	uint32_t crc32;
121	uint32_t calc;
122	size_t bytes;
123	uint8_t *buf;
124	int err;
125
126	buf = kcalloc(1, priv->mtd->size, GFP_KERNEL);
127	if (!buf) {
128		err = -ENOMEM;
129		goto err_out;
130	}
131
132	err = mtd_read(priv->mtd, 0, priv->mtd->size, &bytes, buf);
133	if ((err && !mtd_is_bitflip(err)) || bytes != priv->mtd->size) {
134		dev_err(dev, "Failed to read from mtd: %d\n", err);
135		goto err_kfree;
136	}
137
138	switch (priv->format) {
139	case U_BOOT_FORMAT_SINGLE:
140		crc32_offset = offsetof(struct u_boot_env_image_single, crc32);
141		crc32_data_offset = offsetof(struct u_boot_env_image_single, data);
142		data_offset = offsetof(struct u_boot_env_image_single, data);
143		break;
144	case U_BOOT_FORMAT_REDUNDANT:
145		crc32_offset = offsetof(struct u_boot_env_image_redundant, crc32);
146		crc32_data_offset = offsetof(struct u_boot_env_image_redundant, data);
147		data_offset = offsetof(struct u_boot_env_image_redundant, data);
148		break;
149	case U_BOOT_FORMAT_BROADCOM:
150		crc32_offset = offsetof(struct u_boot_env_image_broadcom, crc32);
151		crc32_data_offset = offsetof(struct u_boot_env_image_broadcom, data);
152		data_offset = offsetof(struct u_boot_env_image_broadcom, data);
153		break;
154	}
155	crc32 = le32_to_cpu(*(__le32 *)(buf + crc32_offset));
156	crc32_data_len = priv->mtd->size - crc32_data_offset;
157	data_len = priv->mtd->size - data_offset;
158
159	calc = crc32(~0, buf + crc32_data_offset, crc32_data_len) ^ ~0L;
160	if (calc != crc32) {
161		dev_err(dev, "Invalid calculated CRC32: 0x%08x (expected: 0x%08x)\n", calc, crc32);
162		err = -EINVAL;
163		goto err_kfree;
164	}
165
166	buf[priv->mtd->size - 1] = '\0';
167	err = u_boot_env_add_cells(priv, buf, data_offset, data_len);
168	if (err)
169		dev_err(dev, "Failed to add cells: %d\n", err);
170
171err_kfree:
172	kfree(buf);
173err_out:
174	return err;
175}
176
177static int u_boot_env_probe(struct platform_device *pdev)
178{
179	struct nvmem_config config = {
180		.name = "u-boot-env",
181		.reg_read = u_boot_env_read,
182	};
183	struct device *dev = &pdev->dev;
184	struct device_node *np = dev->of_node;
185	struct u_boot_env *priv;
186	int err;
187
188	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
189	if (!priv)
190		return -ENOMEM;
191	priv->dev = dev;
192
193	priv->format = (uintptr_t)of_device_get_match_data(dev);
194
195	priv->mtd = of_get_mtd_device_by_node(np);
196	if (IS_ERR(priv->mtd)) {
197		dev_err_probe(dev, PTR_ERR(priv->mtd), "Failed to get %pOF MTD\n", np);
198		return PTR_ERR(priv->mtd);
199	}
200
201	err = u_boot_env_parse(priv);
202	if (err)
203		return err;
204
205	config.dev = dev;
206	config.cells = priv->cells;
207	config.ncells = priv->ncells;
208	config.priv = priv;
209	config.size = priv->mtd->size;
210
211	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
212}
213
214static const struct of_device_id u_boot_env_of_match_table[] = {
215	{ .compatible = "u-boot,env", .data = (void *)U_BOOT_FORMAT_SINGLE, },
216	{ .compatible = "u-boot,env-redundant-bool", .data = (void *)U_BOOT_FORMAT_REDUNDANT, },
217	{ .compatible = "u-boot,env-redundant-count", .data = (void *)U_BOOT_FORMAT_REDUNDANT, },
218	{ .compatible = "brcm,env", .data = (void *)U_BOOT_FORMAT_BROADCOM, },
219	{},
220};
221
222static struct platform_driver u_boot_env_driver = {
223	.probe = u_boot_env_probe,
224	.driver = {
225		.name = "u_boot_env",
226		.of_match_table = u_boot_env_of_match_table,
227	},
228};
229module_platform_driver(u_boot_env_driver);
230
231MODULE_AUTHOR("Rafał Miłecki");
232MODULE_LICENSE("GPL");
233MODULE_DEVICE_TABLE(of, u_boot_env_of_match_table);