/*
 * w1_ds2805 - w1 family 0d (DS28E05) driver
 *
 * Copyright (c) 2016 Andrew Worsley amworsley@gmail.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/w1.h>

#define W1_EEPROM_DS2805       0x0D

#define W1_F0D_EEPROM_SIZE              128
#define W1_F0D_PAGE_BITS                3
#define W1_F0D_PAGE_SIZE                (1<<W1_F0D_PAGE_BITS)
#define W1_F0D_PAGE_MASK                0x0F

#define W1_F0D_SCRATCH_BITS  1
#define W1_F0D_SCRATCH_SIZE  (1<<W1_F0D_SCRATCH_BITS)
#define W1_F0D_SCRATCH_MASK  (W1_F0D_SCRATCH_SIZE-1)

#define W1_F0D_READ_EEPROM      0xF0
#define W1_F0D_WRITE_EEPROM     0x55
#define W1_F0D_RELEASE          0xFF

#define W1_F0D_CS_OK            0xAA /* Chip Status Ok */

#define W1_F0D_TPROG_MS         16

#define W1_F0D_READ_RETRIES             10
#define W1_F0D_READ_MAXLEN              W1_F0D_EEPROM_SIZE

/*
 * 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_f0d_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;
}

/*
 * Read a block from W1 ROM two times and compares the results.
 * If they are equal they are returned, otherwise the read
 * is repeated W1_F0D_READ_RETRIES times.
 *
 * count must not exceed W1_F0D_READ_MAXLEN.
 */
static int w1_f0d_readblock(struct w1_slave *sl, int off, int count, char *buf)
{
        u8 wrbuf[3];
        u8 cmp[W1_F0D_READ_MAXLEN];
        int tries = W1_F0D_READ_RETRIES;

        do {
                wrbuf[0] = W1_F0D_READ_EEPROM;
                wrbuf[1] = off & 0x7f;
                wrbuf[2] = 0;

                if (w1_reset_select_slave(sl))
                        return -1;

                w1_write_block(sl->master, wrbuf, sizeof(wrbuf));
                w1_read_block(sl->master, buf, count);

                if (w1_reset_select_slave(sl))
                        return -1;

                w1_write_block(sl->master, wrbuf, sizeof(wrbuf));
                w1_read_block(sl->master, cmp, count);

                if (!memcmp(cmp, buf, count))
                        return 0;
        } while (--tries);

        dev_err(&sl->dev, "proof reading failed %d times\n",
                        W1_F0D_READ_RETRIES);

        return -1;
}

static ssize_t w1_f0d_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);
        int todo = count;

        count = w1_f0d_fix_count(off, count, W1_F0D_EEPROM_SIZE);
        if (count == 0)
                return 0;

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

        /* read directly from the EEPROM in chunks of W1_F0D_READ_MAXLEN */
        while (todo > 0) {
                int block_read;

                if (todo >= W1_F0D_READ_MAXLEN)
                        block_read = W1_F0D_READ_MAXLEN;
                else
                        block_read = todo;

                if (w1_f0d_readblock(sl, off, block_read, buf) < 0) {
                        count = -EIO;
                        break;
                }

                todo -= W1_F0D_READ_MAXLEN;
                buf += W1_F0D_READ_MAXLEN;
                off += W1_F0D_READ_MAXLEN;
        }

        mutex_unlock(&sl->master->mutex);

        return count;
}

/*
 * Writes to the scratchpad and reads it back for verification.
 * Then copies the scratchpad to EEPROM.
 * The data must be aligned at W1_F0D_SCRATCH_SIZE bytes and
 * must be W1_F0D_SCRATCH_SIZE bytes long.
 * The master must be locked.
 *
 * @param sl    The slave structure
 * @param addr  Address for the write
 * @param len   length must be <= (W1_F0D_PAGE_SIZE - (addr & W1_F0D_PAGE_MASK))
 * @param data  The data to write
 * @return      0=Success -1=failure
 */
static int w1_f0d_write(struct w1_slave *sl, int addr, int len, const u8 *data)
{
        int tries = W1_F0D_READ_RETRIES;
        u8 wrbuf[3];
        u8 rdbuf[W1_F0D_SCRATCH_SIZE];
        u8 cs;

        if ((addr & 1) || (len != 2)) {
                dev_err(&sl->dev, "%s: bad addr/len -  addr=%#x len=%d\n",
                    __func__, addr, len);
                return -1;
        }

retry:

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

        wrbuf[0] = W1_F0D_WRITE_EEPROM;
        wrbuf[1] = addr & 0xff;
        wrbuf[2] = 0xff; /* ?? from Example */

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

        w1_read_block(sl->master, rdbuf, sizeof(rdbuf));
        /* Compare what was read against the data written */
        if ((rdbuf[0] != data[0]) || (rdbuf[1] != data[1])) {

                if (--tries)
                        goto retry;

                dev_err(&sl->dev,
                        "could not write to eeprom, scratchpad compare failed %d times\n",
                        W1_F0D_READ_RETRIES);
                pr_info("%s: rdbuf = %#x %#x data = %#x %#x\n",
                    __func__, rdbuf[0], rdbuf[1], data[0], data[1]);

                return -1;
        }

        /* Trigger write out to EEPROM */
        w1_write_8(sl->master, W1_F0D_RELEASE);

        /* Sleep for tprog ms to wait for the write to complete */
        msleep(W1_F0D_TPROG_MS);

        /* Check CS (Command Status) == 0xAA ? */
        cs = w1_read_8(sl->master);
        if (cs != W1_F0D_CS_OK) {
                dev_err(&sl->dev, "save to eeprom failed = CS=%#x\n", cs);
                return -1;
        }

        return 0;
}

static ssize_t w1_f0d_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;
        int copy;

        count = w1_f0d_fix_count(off, count, W1_F0D_EEPROM_SIZE);
        if (count == 0)
                return 0;

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

        /* Can only write data in blocks of the size of the scratchpad */
        addr = off;
        len = count;
        while (len > 0) {

                /* if len too short or addr not aligned */
                if (len < W1_F0D_SCRATCH_SIZE || addr & W1_F0D_SCRATCH_MASK) {
                        char tmp[W1_F0D_SCRATCH_SIZE];

                        /* read the block and update the parts to be written */
                        if (w1_f0d_readblock(sl, addr & ~W1_F0D_SCRATCH_MASK,
                                        W1_F0D_SCRATCH_SIZE, tmp)) {
                                count = -EIO;
                                goto out_up;
                        }

                        /* copy at most to the boundary of the PAGE or len */
                        copy = W1_F0D_SCRATCH_SIZE -
                                (addr & W1_F0D_SCRATCH_MASK);

                        if (copy > len)
                                copy = len;

                        memcpy(&tmp[addr & W1_F0D_SCRATCH_MASK], buf, copy);
                        if (w1_f0d_write(sl, addr & ~W1_F0D_SCRATCH_MASK,
                                        W1_F0D_SCRATCH_SIZE, tmp) < 0) {
                                count = -EIO;
                                goto out_up;
                        }
                } else {

                        copy = W1_F0D_SCRATCH_SIZE;
                        if (w1_f0d_write(sl, addr, copy, buf) < 0) {
                                count = -EIO;
                                goto out_up;
                        }
                }
                buf += copy;
                addr += copy;
                len -= copy;
        }

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

        return count;
}

static struct bin_attribute w1_f0d_bin_attr = {
        .attr = {
                .name = "eeprom",
                .mode = S_IRUGO | S_IWUSR,
        },
        .size = W1_F0D_EEPROM_SIZE,
        .read = w1_f0d_read_bin,
        .write = w1_f0d_write_bin,
};

static int w1_f0d_add_slave(struct w1_slave *sl)
{
        return sysfs_create_bin_file(&sl->dev.kobj, &w1_f0d_bin_attr);
}

static void w1_f0d_remove_slave(struct w1_slave *sl)
{
        sysfs_remove_bin_file(&sl->dev.kobj, &w1_f0d_bin_attr);
}

static struct w1_family_ops w1_f0d_fops = {
        .add_slave      = w1_f0d_add_slave,
        .remove_slave   = w1_f0d_remove_slave,
};

static struct w1_family w1_family_2d = {
        .fid = W1_EEPROM_DS2805,
        .fops = &w1_f0d_fops,
};

static int __init w1_f0d_init(void)
{
        pr_info("%s()\n", __func__);
        return w1_register_family(&w1_family_2d);
}

static void __exit w1_f0d_fini(void)
{
        pr_info("%s()\n", __func__);
        w1_unregister_family(&w1_family_2d);
}

module_init(w1_f0d_init);
module_exit(w1_f0d_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andrew Worsley amworsley@gmail.com");
MODULE_DESCRIPTION("w1 family 0d driver for DS2805, 1kb EEPROM");