/*
 *      w1_ds2433.c - w1 family 23 (DS2433) driver
 *
 * Copyright (c) 2005 Ben Gardner <bgardner@wabtec.com>
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2. See the file COPYING for more details.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/slab.h>
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
#include <linux/crc16.h>

#define CRC16_INIT              0
#define CRC16_VALID             0xb001

#endif

#include "../w1.h"
#include "../w1_int.h"
#include "../w1_family.h"

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
MODULE_DESCRIPTION("w1 family 23 driver for DS2433, 4kb EEPROM");

#define W1_EEPROM_SIZE          512
#define W1_PAGE_COUNT           16
#define W1_PAGE_SIZE            32
#define W1_PAGE_BITS            5
#define W1_PAGE_MASK            0x1F

#define W1_F23_TIME             300

#define W1_F23_READ_EEPROM      0xF0
#define W1_F23_WRITE_SCRATCH    0x0F
#define W1_F23_READ_SCRATCH     0xAA
#define W1_F23_COPY_SCRATCH     0x55

struct w1_f23_data {
        u8      memory[W1_EEPROM_SIZE];
        u32     validcrc;
};

/**
 * Check the file size bounds and adjusts count as needed.
 * This would not be needed if the file size didn't reset to 0 after a write.
 */
static inline size_t w1_f23_fix_count(loff_t off, size_t count, size_t size)
{
        if (off > size)
                return 0;

        if ((off + count) > size)
                return (size - off);

        return count;
}

#ifdef CONFIG_W1_SLAVE_DS2433_CRC
static int w1_f23_refresh_block(struct w1_slave *sl, struct w1_f23_data *data,
                                int block)
{
        u8      wrbuf[3];
        int     off = block * W1_PAGE_SIZE;

        if (data->validcrc & (1 << block))
                return 0;

        if (w1_reset_select_slave(sl)) {
                data->validcrc = 0;
                return -EIO;
        }

        wrbuf[0] = W1_F23_READ_EEPROM;
        wrbuf[1] = off & 0xff;
        wrbuf[2] = off >> 8;
        w1_write_block(sl->master, wrbuf, 3);
        w1_read_block(sl->master, &data->memory[off], W1_PAGE_SIZE);

        /* cache the block if the CRC is valid */
        if (crc16(CRC16_INIT, &data->memory[off], W1_PAGE_SIZE) == CRC16_VALID)
                data->validcrc |= (1 << block);

        return 0;
}
#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */

static ssize_t w1_f23_read_bin(struct file *filp, struct kobject *kobj,
                               struct bin_attribute *bin_attr,
                               char *buf, loff_t off, size_t count)
{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        struct w1_f23_data *data = sl->family_data;
        int i, min_page, max_page;
#else
        u8 wrbuf[3];
#endif

        if ((count = w1_f23_fix_count(off, count, W1_EEPROM_SIZE)) == 0)
                return 0;

        mutex_lock(&sl->master->bus_mutex);

#ifdef CONFIG_W1_SLAVE_DS2433_CRC

        min_page = (off >> W1_PAGE_BITS);
        max_page = (off + count - 1) >> W1_PAGE_BITS;
        for (i = min_page; i <= max_page; i++) {
                if (w1_f23_refresh_block(sl, data, i)) {
                        count = -EIO;
                        goto out_up;
                }
        }
        memcpy(buf, &data->memory[off], count);

#else   /* CONFIG_W1_SLAVE_DS2433_CRC */

        /* read directly from the EEPROM */
        if (w1_reset_select_slave(sl)) {
                count = -EIO;
                goto out_up;
        }

        wrbuf[0] = W1_F23_READ_EEPROM;
        wrbuf[1] = off & 0xff;
        wrbuf[2] = off >> 8;
        w1_write_block(sl->master, wrbuf, 3);
        w1_read_block(sl->master, buf, count);

#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */

out_up:
        mutex_unlock(&sl->master->bus_mutex);

        return count;
}

/**
 * Writes to the scratchpad and reads it back for verification.
 * Then copies the scratchpad to EEPROM.
 * The data must be on one page.
 * The master must be locked.
 *
 * @param sl    The slave structure
 * @param addr  Address for the write
 * @param len   length must be <= (W1_PAGE_SIZE - (addr & W1_PAGE_MASK))
 * @param data  The data to write
 * @return      0=Success -1=failure
 */
static int w1_f23_write(struct w1_slave *sl, int addr, int len, const u8 *data)
{
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        struct w1_f23_data *f23 = sl->family_data;
#endif
        u8 wrbuf[4];
        u8 rdbuf[W1_PAGE_SIZE + 3];
        u8 es = (addr + len - 1) & 0x1f;

        /* Write the data to the scratchpad */
        if (w1_reset_select_slave(sl))
                return -1;

        wrbuf[0] = W1_F23_WRITE_SCRATCH;
        wrbuf[1] = addr & 0xff;
        wrbuf[2] = addr >> 8;

        w1_write_block(sl->master, wrbuf, 3);
        w1_write_block(sl->master, data, len);

        /* Read the scratchpad and verify */
        if (w1_reset_select_slave(sl))
                return -1;

        w1_write_8(sl->master, W1_F23_READ_SCRATCH);
        w1_read_block(sl->master, rdbuf, len + 3);

        /* Compare what was read against the data written */
        if ((rdbuf[0] != wrbuf[1]) || (rdbuf[1] != wrbuf[2]) ||
            (rdbuf[2] != es) || (memcmp(data, &rdbuf[3], len) != 0))
                return -1;

        /* Copy the scratchpad to EEPROM */
        if (w1_reset_select_slave(sl))
                return -1;

        wrbuf[0] = W1_F23_COPY_SCRATCH;
        wrbuf[3] = es;
        w1_write_block(sl->master, wrbuf, 4);

        /* Sleep for 5 ms to wait for the write to complete */
        msleep(5);

        /* Reset the bus to wake up the EEPROM (this may not be needed) */
        w1_reset_bus(sl->master);
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        f23->validcrc &= ~(1 << (addr >> W1_PAGE_BITS));
#endif
        return 0;
}

static ssize_t w1_f23_write_bin(struct file *filp, struct kobject *kobj,
                                struct bin_attribute *bin_attr,
                                char *buf, loff_t off, size_t count)
{
        struct w1_slave *sl = kobj_to_w1_slave(kobj);
        int addr, len, idx;

        if ((count = w1_f23_fix_count(off, count, W1_EEPROM_SIZE)) == 0)
                return 0;

#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        /* can only write full blocks in cached mode */
        if ((off & W1_PAGE_MASK) || (count & W1_PAGE_MASK)) {
                dev_err(&sl->dev, "invalid offset/count off=%d cnt=%zd\n",
                        (int)off, count);
                return -EINVAL;
        }

        /* make sure the block CRCs are valid */
        for (idx = 0; idx < count; idx += W1_PAGE_SIZE) {
                if (crc16(CRC16_INIT, &buf[idx], W1_PAGE_SIZE) != CRC16_VALID) {
                        dev_err(&sl->dev, "bad CRC at offset %d\n", (int)off);
                        return -EINVAL;
                }
        }
#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */

        mutex_lock(&sl->master->bus_mutex);

        /* Can only write data to one page at a time */
        idx = 0;
        while (idx < count) {
                addr = off + idx;
                len = W1_PAGE_SIZE - (addr & W1_PAGE_MASK);
                if (len > (count - idx))
                        len = count - idx;

                if (w1_f23_write(sl, addr, len, &buf[idx]) < 0) {
                        count = -EIO;
                        goto out_up;
                }
                idx += len;
        }

out_up:
        mutex_unlock(&sl->master->bus_mutex);

        return count;
}

static struct bin_attribute w1_f23_bin_attr = {
        .attr = {
                .name = "eeprom",
                .mode = S_IRUGO | S_IWUSR,
        },
        .size = W1_EEPROM_SIZE,
        .read = w1_f23_read_bin,
        .write = w1_f23_write_bin,
};

static int w1_f23_add_slave(struct w1_slave *sl)
{
        int err;
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        struct w1_f23_data *data;

        data = kzalloc(sizeof(struct w1_f23_data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        sl->family_data = data;

#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */

        err = sysfs_create_bin_file(&sl->dev.kobj, &w1_f23_bin_attr);

#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        if (err)
                kfree(data);
#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */

        return err;
}

static void w1_f23_remove_slave(struct w1_slave *sl)
{
#ifdef CONFIG_W1_SLAVE_DS2433_CRC
        kfree(sl->family_data);
        sl->family_data = NULL;
#endif  /* CONFIG_W1_SLAVE_DS2433_CRC */
        sysfs_remove_bin_file(&sl->dev.kobj, &w1_f23_bin_attr);
}

static struct w1_family_ops w1_f23_fops = {
        .add_slave      = w1_f23_add_slave,
        .remove_slave   = w1_f23_remove_slave,
};

static struct w1_family w1_family_23 = {
        .fid = W1_EEPROM_DS2433,
        .fops = &w1_f23_fops,
};

static int __init w1_f23_init(void)
{
        return w1_register_family(&w1_family_23);
}

static void __exit w1_f23_fini(void)
{
        w1_unregister_family(&w1_family_23);
}

module_init(w1_f23_init);
module_exit(w1_f23_fini);