/*
 * rawio_i2c.c - rawio I2C driver.
 * Read or write a I2C device's register, based on the rawio framework.
 *
 * Copyright (c) 2013 Bin Gao <bin.gao@intel.com>
 *
 * This file is released under the GPLv2
 *
 *
 * read i2c registers:
 * echo "r i2c <bus_num> <slace_addr> <reg> [<len>]" >
 *			/sys/kernel/debug/rawio_cmd
 * cat /sys/kernel/debug/rawio_output
 * e.g. echo "r i2c 3 0x6b 0x84 5" > /sys/kernel/debug/rawio_cmd
 *      cat /sys/kernel/debug/rawio_output
 *
 * write a i2c register:
 * echo "w i2c <bus_num> <slace_addr> <reg> <val>" >
 *			/sys/kernel/debug/rawio_cmd
 * cat /sys/kernel/debug/rawio_output
 * e.g. echo "w i2c 4 0x70 0x4 0xfa" > /sys/kernel/debug/rawio_cmd
 *      cat /sys/kernel/debug/rawio_output
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/pm_runtime.h>
#include <linux/i2c.h>
#include "rawio.h"

static int i2c_prepare(u8 i2c_bus, u16 i2c_addr, u16 i2c_reg, u16 len,
			int ten_bit_addr, struct i2c_adapter **ppadap)
{
	struct i2c_adapter *adap;

	adap = i2c_get_adapter((int)i2c_bus);
	if (!adap) {
		rawio_err("can't find bus adapter for i2c bus %d\n",
			i2c_bus);
		return -ENODEV;
	}

	if ((!ten_bit_addr && (i2c_addr > 128)) || (i2c_addr > 1024)) {
		rawio_err("register address is out of range, forgot 't' for 10bit addr?\n");
		return -EINVAL;
	}

	if ((!ten_bit_addr && ((i2c_addr + len) > 128)) ||
			((i2c_addr + len) > 1024)) {
		rawio_err("register address is out of range, forgot 't' for 10bit addr?\n");
		return -EINVAL;
	}

	*ppadap = adap;
	return 0;
}

static int rawio_i2c_read(struct rawio_driver *driver, int width, u64 *input,
	u8 *postfix, int input_num, void **output, int *output_num)
{
	int ret, len;
	struct i2c_adapter *adap;
	u16 i2c_addr, i2c_reg;
	struct i2c_msg msg[2];
	u8 i2c_bus, buf[2], *out_buf, ten_bit_addr, sixteen_bit_reg;

	i2c_bus = (u8)input[0];
	i2c_addr = (u16)input[1];
	i2c_reg = (u16)input[2];

	len = 1;
	if (input_num == 4)
		len = (u16)input[3];

	ten_bit_addr = postfix[1];
	sixteen_bit_reg = postfix[2];

	ret = i2c_prepare(i2c_bus, i2c_addr, i2c_reg, len, ten_bit_addr, &adap);
	if (ret)
		return ret;

	out_buf = kzalloc(sizeof(u8) * len, GFP_KERNEL);
	if (buf == NULL) {
		rawio_err("can't alloc memory\n");
		return -ENOMEM;
	}
	buf[0] = i2c_reg & 0xff;
	buf[1] = (i2c_reg >> 8) & 0xff;

	/* write i2c reg address */
	msg[0].addr = i2c_addr;
	msg[0].flags = ten_bit_addr ? I2C_M_TEN : 0;
	msg[0].len = sixteen_bit_reg ? 2 : 1;
	msg[0].buf = buf;

	/* read i2c reg */
	msg[1].addr = i2c_addr;
	msg[1].flags = I2C_M_RD | (ten_bit_addr ? I2C_M_TEN : 0);
	msg[1].len = len;
	msg[1].buf = out_buf;

	ret = i2c_transfer(adap, msg, 2);
	if (ret != 2) {
		rawio_err("i2c_transfer() failed, ret = %d\n", ret);
		kfree(out_buf);
		return -EIO;
	}

	*output = out_buf;
	*output_num = len;
	return 0;
}

static int rawio_i2c_write(struct rawio_driver *driver, int width, u64 *input,
			u8 *postfix, int input_num)
{
	int ret;
	struct i2c_adapter *adap;
	u16 i2c_addr, i2c_reg;
	struct i2c_msg msg;
	u8 value, i2c_bus, buf[2], buf16[3], ten_bit_addr, sixteen_bit_reg;

	i2c_bus = (u8)input[0];
	i2c_addr = (u8)input[1];
	i2c_reg = (u16)input[2];
	value = (u8)input[3];

	ten_bit_addr = postfix[1];
	sixteen_bit_reg = postfix[2];

	ret = i2c_prepare(i2c_bus, i2c_addr, i2c_reg, 0, ten_bit_addr, &adap);
	if (ret)
		return ret;

	if (sixteen_bit_reg) {
		buf16[0] = (i2c_reg >> 8) & 0xff; /* high 8 bit reg addr */
		buf16[1] = i2c_reg & 0xff; /* low 8 bit reg addr */
		buf16[2] = value;
		msg.len = 3;
		msg.buf = buf16;
	} else {
		buf[0] = i2c_reg & 0xff; /* low 8 bit reg addr */
		buf[1] = value;
		msg.len = 2;
		msg.buf = buf;
	}

	msg.addr = i2c_addr;
	msg.flags = ten_bit_addr ? I2C_M_TEN : 0;

	ret = i2c_transfer(adap, &msg, 1);
	if (ret != 1) {
		rawio_err("i2c_transfer() failed, ret = %d\n", ret);
		return -EIO;
	}

	return 0;
}

static struct rawio_ops rawio_i2c_ops = {
	rawio_i2c_read,
	NULL,
	rawio_i2c_write,
};

static struct rawio_driver rawio_i2c = {
	{NULL, NULL}, /* list node */
	"i2c", /* driver name */

	/* read */
	4, /* max args */
	{TYPE_U8, TYPE_U16, TYPE_U16, TYPE_U8}, /* type of read args */
	3, /* min args */
	{ 0, 't', 's', 0 }, /* args postfix */

	/* write */
	4, /* max args */
	{TYPE_U8, TYPE_U16, TYPE_U16, TYPE_U8}, /* type of write args */
	4, /* min args */
	{ 0, 't', 's', 0 }, /* args postfix */

	2, /* index of arg that specifies the register or memory address */

	WIDTH_1, /* supported width */
	WIDTH_1, /* default width */

	/*
	 * Slave address with postfix 't' indicates 10 bit slave address,
	 * otherwise it's 7 bit address by default.
	 * Register offset with postfix 's' indicates register offset is
	 * 16 bit, otherwise it's 8 bit offset by default.
	 * For example "r i2c 5 0x108t 0x0394s 2" means 10 bit slave address
	 * and 16 bit register offset, and "r i2c 5 0x28 0x74" means 7 bit
	 * slave address and 8 bit register offset.
	 */
	"r i2c <bus> <addr>[t] <reg>[s] [<len>]\n"
	"w i2c <bus> <addr>[t] <reg>[s] <val>\n",
	&rawio_i2c_ops,
	NULL
};

static int __init rawio_i2c_init(void)
{
	if (rawio_register_driver(&rawio_i2c))
		return -ENODEV;

	return 0;
}
module_init(rawio_i2c_init);

static void __exit rawio_i2c_exit(void)
{
	rawio_unregister_driver(&rawio_i2c);
}
module_exit(rawio_i2c_exit);

MODULE_DESCRIPTION("Rawio I2C driver");
MODULE_VERSION("1.0");
MODULE_AUTHOR("Bin Gao <bin.gao@intel.com>");
MODULE_LICENSE("GPL v2");