// SPDX-License-Identifier: GPL-2.0

#include <linux/crc8.h>
#include <linux/etherdevice.h>
#include <linux/nvmem-consumer.h>
#include <linux/nvmem-provider.h>
#include <linux/of.h>
#include <uapi/linux/if_ether.h>

#define SL28VPD_MAGIC 'V'

struct sl28vpd_header {
        u8 magic;
        u8 version;
} __packed;

struct sl28vpd_v1 {
        struct sl28vpd_header header;
        char serial_number[15];
        u8 base_mac_address[ETH_ALEN];
        u8 crc8;
} __packed;

static int sl28vpd_mac_address_pp(void *priv, const char *id, int index,
                                  unsigned int offset, void *buf,
                                  size_t bytes)
{
        if (bytes != ETH_ALEN)
                return -EINVAL;

        if (index < 0)
                return -EINVAL;

        if (!is_valid_ether_addr(buf))
                return -EINVAL;

        eth_addr_add(buf, index);

        return 0;
}

static const struct nvmem_cell_info sl28vpd_v1_entries[] = {
        {
                .name = "serial-number",
                .offset = offsetof(struct sl28vpd_v1, serial_number),
                .bytes = sizeof_field(struct sl28vpd_v1, serial_number),
        },
        {
                .name = "base-mac-address",
                .offset = offsetof(struct sl28vpd_v1, base_mac_address),
                .bytes = sizeof_field(struct sl28vpd_v1, base_mac_address),
                .read_post_process = sl28vpd_mac_address_pp,
        },
};

static int sl28vpd_v1_check_crc(struct device *dev, struct nvmem_device *nvmem)
{
        struct sl28vpd_v1 data_v1;
        u8 table[CRC8_TABLE_SIZE];
        int ret;
        u8 crc;

        crc8_populate_msb(table, 0x07);

        ret = nvmem_device_read(nvmem, 0, sizeof(data_v1), &data_v1);
        if (ret < 0)
                return ret;
        else if (ret != sizeof(data_v1))
                return -EIO;

        crc = crc8(table, (void *)&data_v1, sizeof(data_v1) - 1, 0);

        if (crc != data_v1.crc8) {
                dev_err(dev,
                        "Checksum is invalid (got %02x, expected %02x).\n",
                        crc, data_v1.crc8);
                return -EINVAL;
        }

        return 0;
}

static int sl28vpd_add_cells(struct nvmem_layout *layout)
{
        struct nvmem_device *nvmem = layout->nvmem;
        struct device *dev = &layout->dev;
        const struct nvmem_cell_info *pinfo;
        struct nvmem_cell_info info = {0};
        struct device_node *layout_np;
        struct sl28vpd_header hdr;
        int ret, i;

        /* check header */
        ret = nvmem_device_read(nvmem, 0, sizeof(hdr), &hdr);
        if (ret < 0)
                return ret;
        else if (ret != sizeof(hdr))
                return -EIO;

        if (hdr.magic != SL28VPD_MAGIC) {
                dev_err(dev, "Invalid magic value (%02x)\n", hdr.magic);
                return -EINVAL;
        }

        if (hdr.version != 1) {
                dev_err(dev, "Version %d is unsupported.\n", hdr.version);
                return -EINVAL;
        }

        ret = sl28vpd_v1_check_crc(dev, nvmem);
        if (ret)
                return ret;

        layout_np = of_nvmem_layout_get_container(nvmem);
        if (!layout_np)
                return -ENOENT;

        for (i = 0; i < ARRAY_SIZE(sl28vpd_v1_entries); i++) {
                pinfo = &sl28vpd_v1_entries[i];

                info.name = pinfo->name;
                info.offset = pinfo->offset;
                info.bytes = pinfo->bytes;
                info.read_post_process = pinfo->read_post_process;
                info.np = of_get_child_by_name(layout_np, pinfo->name);

                ret = nvmem_add_one_cell(nvmem, &info);
                if (ret) {
                        of_node_put(layout_np);
                        return ret;
                }
        }

        of_node_put(layout_np);

        return 0;
}

static int sl28vpd_probe(struct nvmem_layout *layout)
{
        layout->add_cells = sl28vpd_add_cells;

        return nvmem_layout_register(layout);
}

static void sl28vpd_remove(struct nvmem_layout *layout)
{
        nvmem_layout_unregister(layout);
}

static const struct of_device_id sl28vpd_of_match_table[] = {
        { .compatible = "kontron,sl28-vpd" },
        {},
};
MODULE_DEVICE_TABLE(of, sl28vpd_of_match_table);

static struct nvmem_layout_driver sl28vpd_layout = {
        .driver = {
                .name = "kontron-sl28vpd-layout",
                .of_match_table = sl28vpd_of_match_table,
        },
        .probe = sl28vpd_probe,
        .remove = sl28vpd_remove,
};
module_nvmem_layout_driver(sl28vpd_layout);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
MODULE_DESCRIPTION("NVMEM layout driver for the VPD of Kontron sl28 boards");