/*
 *  scst_modisk.c
 *
 *  Copyright (C) 2004 - 2018 Vladislav Bolkhovitin <vst@vlnb.net>
 *  Copyright (C) 2004 - 2005 Leonid Stoljar
 *  Copyright (C) 2007 - 2018 Western Digital Corporation
 *
 *  SCSI MO disk (type 7) dev handler
 *  &
 *  SCSI MO disk (type 7) "performance" device handler (skip all READ and WRITE
 *   operations).
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation, version 2
 *  of the License.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <scsi/scsi_host.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#define LOG_PREFIX             "dev_modisk"

#ifdef INSIDE_KERNEL_TREE
#include <scst/scst.h>
#else
#include "scst.h"
#endif
#include "scst_dev_handler.h"

# define MODISK_NAME           "dev_modisk"
# define MODISK_PERF_NAME      "dev_modisk_perf"

#define MODISK_DEF_BLOCK_SHIFT    10

static int modisk_attach(struct scst_device *);
static void modisk_detach(struct scst_device *);
static int modisk_parse(struct scst_cmd *);
static int modisk_done(struct scst_cmd *);
static enum scst_exec_res modisk_perf_exec(struct scst_cmd *);

static struct scst_dev_type modisk_devtype = {
	.name =			MODISK_NAME,
	.type =			TYPE_MOD,
	.threads_num =		1,
	.parse_atomic =		1,
	.dev_done_atomic =	1,
	.attach =		modisk_attach,
	.detach =		modisk_detach,
	.parse =		modisk_parse,
	.dev_done =		modisk_done,
#if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
	.default_trace_flags =	SCST_DEFAULT_DEV_LOG_FLAGS,
	.trace_flags =		&trace_flag,
#endif
};

static struct scst_dev_type modisk_devtype_perf = {
	.name =			MODISK_PERF_NAME,
	.type =			TYPE_MOD,
	.parse_atomic =		1,
	.dev_done_atomic =	1,
	.attach =		modisk_attach,
	.detach =		modisk_detach,
	.parse =		modisk_parse,
	.dev_done =		modisk_done,
	.exec =			modisk_perf_exec,
#if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
	.default_trace_flags =	SCST_DEFAULT_DEV_LOG_FLAGS,
	.trace_flags =		&trace_flag,
#endif
};

static int __init init_scst_modisk_driver(void)
{
	int res = 0;

	TRACE_ENTRY();

	modisk_devtype.module = THIS_MODULE;

	res = scst_register_dev_driver(&modisk_devtype);
	if (res < 0)
		goto out;

	modisk_devtype_perf.module = THIS_MODULE;

	res = scst_register_dev_driver(&modisk_devtype_perf);
	if (res < 0)
		goto out_unreg;


out:
	TRACE_EXIT_RES(res);
	return res;


out_unreg:
	scst_unregister_dev_driver(&modisk_devtype);
	goto out;
}

static void __exit exit_scst_modisk_driver(void)
{
	TRACE_ENTRY();

	scst_unregister_dev_driver(&modisk_devtype_perf);
	scst_unregister_dev_driver(&modisk_devtype);

	TRACE_EXIT();
	return;
}

module_init(init_scst_modisk_driver);
module_exit(exit_scst_modisk_driver);

static int modisk_attach(struct scst_device *dev)
{
	int res, rc;
	uint8_t cmd[10];
	const int buffer_size = 512;
	uint8_t *buffer = NULL;
	int retries;
	unsigned char sense_buffer[SCSI_SENSE_BUFFERSIZE];
	enum dma_data_direction data_dir;

	TRACE_ENTRY();

	if (dev->scsi_dev == NULL ||
	    dev->scsi_dev->type != dev->type) {
		PRINT_ERROR("%s", "SCSI device not define or illegal type");
		res = -ENODEV;
		goto out;
	}

	dev->block_shift = MODISK_DEF_BLOCK_SHIFT;
	dev->block_size = 1 << dev->block_shift;

	/*
	 * If the device is offline, don't try to read capacity or any
	 * of the other stuff
	 */
	if (dev->scsi_dev->sdev_state == SDEV_OFFLINE) {
		TRACE_DBG("%s", "Device is offline");
		res = -ENODEV;
		goto out;
	}

	buffer = kmalloc(buffer_size, GFP_KERNEL);
	if (!buffer) {
		PRINT_ERROR("Buffer memory allocation (size %d) failure",
			buffer_size);
		res = -ENOMEM;
		goto out;
	}

	/*
	 * Clear any existing UA's and get modisk capacity (modisk block
	 * size).
	 */
	memset(cmd, 0, sizeof(cmd));
	cmd[0] = READ_CAPACITY;
	cmd[1] = (dev->scsi_dev->scsi_level <= SCSI_2) ?
	    ((dev->scsi_dev->lun << 5) & 0xe0) : 0;
	retries = SCST_DEV_RETRIES_ON_UA;
	while (1) {
		memset(buffer, 0, buffer_size);
		memset(sense_buffer, 0, sizeof(sense_buffer));
		data_dir = SCST_DATA_READ;

		TRACE_DBG("%s", "Doing READ_CAPACITY");
		rc = scst_scsi_execute(dev->scsi_dev, cmd, data_dir, buffer,
				       buffer_size, sense_buffer,
				       SCST_GENERIC_MODISK_REG_TIMEOUT, 3, 0);

		TRACE_DBG("READ_CAPACITY done: %x", rc);

		if (!rc || !scst_analyze_sense(sense_buffer,
				sizeof(sense_buffer), SCST_SENSE_KEY_VALID,
				UNIT_ATTENTION, 0, 0))
			break;

		if (!--retries) {
			PRINT_ERROR("UA not cleared after %d retries",
				    SCST_DEV_RETRIES_ON_UA);
			res = -ENODEV;
			goto out_free_buf;
		}
	}

	if (rc == 0) {
		uint32_t sector_size = get_unaligned_be32(&buffer[4]);

		if (sector_size == 0)
			dev->block_shift = MODISK_DEF_BLOCK_SHIFT;
		else
			dev->block_shift = scst_calc_block_shift(sector_size);
		TRACE_DBG("Sector size is %i scsi_level %d(SCSI_2 %d)",
		      sector_size, dev->scsi_dev->scsi_level, SCSI_2);
		if (dev->block_shift < 9) {
			PRINT_ERROR("READ CAPACITY reported an invalid sector size: %d",
				    sector_size);
			res = -EINVAL;
			goto out_free_buf;
		}
	} else {
		dev->block_shift = MODISK_DEF_BLOCK_SHIFT;
		TRACE(TRACE_MINOR, "Read capacity failed: %x, using default "
			"sector size %d", rc, dev->block_shift);
		PRINT_BUFF_FLAG(TRACE_MINOR, "Returned sense", sense_buffer,
			sizeof(sense_buffer));
	}
	dev->block_size = 1 << dev->block_shift;

	res = scst_obtain_device_parameters(dev, NULL);
	if (res != 0) {
		PRINT_ERROR("Failed to obtain control parameters for device "
			"%s: %x", dev->virt_name, res);
		goto out_free_buf;
	}

out_free_buf:
	kfree(buffer);

out:
	TRACE_EXIT_RES(res);
	return res;
}

static void modisk_detach(struct scst_device *dev)
{
	/* Nothing to do */
	return;
}

static int modisk_parse(struct scst_cmd *cmd)
{
	int res = SCST_CMD_STATE_DEFAULT, rc;

	rc = scst_modisk_generic_parse(cmd);
	if (rc != 0) {
		res = scst_get_cmd_abnormal_done_state(cmd);
		goto out;
	}

	cmd->retries = SCST_PASSTHROUGH_RETRIES;
out:
	return res;
}

static void modisk_set_block_shift(struct scst_cmd *cmd, int block_shift)
{
	struct scst_device *dev = cmd->dev;
	int new_block_shift;

	/*
	 * No need for locks here, since *_detach() can not be
	 * called, when there are existing commands.
	 */
	new_block_shift = block_shift ? : MODISK_DEF_BLOCK_SHIFT;
	if (dev->block_shift != new_block_shift) {
		PRINT_INFO("%s: Changed block shift from %d into %d / %d",
			   dev->virt_name, dev->block_shift, block_shift,
			   new_block_shift);
		dev->block_shift = new_block_shift;
		dev->block_size = 1 << dev->block_shift;
	}
	return;
}

static int modisk_done(struct scst_cmd *cmd)
{
	int res;

	TRACE_ENTRY();

	res = scst_block_generic_dev_done(cmd, modisk_set_block_shift);

	TRACE_EXIT_RES(res);
	return res;
}

static enum scst_exec_res modisk_perf_exec(struct scst_cmd *cmd)
{
	enum scst_exec_res res = SCST_EXEC_NOT_COMPLETED;
	int opcode = cmd->cdb[0];

	TRACE_ENTRY();

	cmd->status = 0;
	cmd->msg_status = 0;
	cmd->host_status = DID_OK;
	cmd->driver_status = 0;

	switch (opcode) {
	case WRITE_6:
	case WRITE_10:
	case WRITE_12:
	case WRITE_16:
	case READ_6:
	case READ_10:
	case READ_12:
	case READ_16:
		cmd->completed = 1;
		goto out_done;
	}

out:
	TRACE_EXIT_RES(res);
	return res;

out_done:
	res = SCST_EXEC_COMPLETED;
	cmd->scst_cmd_done(cmd, SCST_CMD_STATE_DEFAULT, SCST_CONTEXT_SAME);
	goto out;
}

MODULE_AUTHOR("Vladislav Bolkhovitin & Leonid Stoljar");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SCSI MO disk (type 7) dev handler for SCST");
MODULE_VERSION(SCST_VERSION_STRING);