#include <linux/slab.h>
#include <linux/module.h>
#include <linux/mutex.h>

#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_devinfo.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_eh.h>

#include "usb.h"
#include "scsiglue.h"
#include "transport.h"

/* Host functions */
//----- host_info() ---------------------
static const char* host_info(struct Scsi_Host *host)
{
	//printk("scsiglue --- host_info\n");
	return "SCSI emulation for USB Mass Storage devices";
}

//----- slave_alloc() ---------------------
static int slave_alloc(struct scsi_device *sdev)
{
	struct us_data *us = host_to_us(sdev->host);

	//printk("scsiglue --- slave_alloc\n");
	sdev->inquiry_len = 36;

	blk_queue_update_dma_alignment(sdev->request_queue, (512 - 1));

	if (us->subclass == USB_SC_UFI)
		sdev->sdev_target->pdt_1f_for_no_lun = 1;

	return 0;
}

//----- slave_configure() ---------------------
static int slave_configure(struct scsi_device *sdev)
{
	struct us_data *us = host_to_us(sdev->host);

	//printk("scsiglue --- slave_configure\n");
	if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN))
	{
		unsigned int max_sectors = 64;

		if (us->fflags & US_FL_MAX_SECTORS_MIN)
			max_sectors = PAGE_CACHE_SIZE >> 9;
		if (queue_max_sectors(sdev->request_queue) > max_sectors)
			blk_queue_max_hw_sectors(sdev->request_queue,
					      max_sectors);
	}

	if (sdev->type == TYPE_DISK)
	{
		if (us->subclass != USB_SC_SCSI && us->subclass != USB_SC_CYP_ATACB)
			sdev->use_10_for_ms = 1;
		sdev->use_192_bytes_for_3f = 1;
		if (us->fflags & US_FL_NO_WP_DETECT)
			sdev->skip_ms_page_3f = 1;
		sdev->skip_ms_page_8 = 1;
		if (us->fflags & US_FL_FIX_CAPACITY)
			sdev->fix_capacity = 1;
		if (us->fflags & US_FL_CAPACITY_HEURISTICS)
			sdev->guess_capacity = 1;
		if (sdev->scsi_level > SCSI_2)
			sdev->sdev_target->scsi_level = sdev->scsi_level = SCSI_2;
		sdev->retry_hwerror = 1;
		sdev->allow_restart = 1;
		sdev->last_sector_bug = 1;
	}
	else
	{
		sdev->use_10_for_ms = 1;
	}

	if ((us->protocol == USB_PR_CB || us->protocol == USB_PR_CBI) && sdev->scsi_level == SCSI_UNKNOWN)
		us->max_lun = 0;

	if (us->fflags & US_FL_NOT_LOCKABLE)
		sdev->lockable = 0;

	return 0;
}

/* This is always called with scsi_lock(host) held */
//----- queuecommand() ---------------------
static int queuecommand_lck(struct scsi_cmnd *srb, void (*done)(struct scsi_cmnd *))
{
	struct us_data *us = host_to_us(srb->device->host);

	//printk("scsiglue --- queuecommand\n");

	/* check for state-transition errors */
	if (us->srb != NULL)
	{
		printk("Error in %s: us->srb = %p\n", __FUNCTION__, us->srb);
		return SCSI_MLQUEUE_HOST_BUSY;
	}

	/* fail the command if we are disconnecting */
	if (test_bit(US_FLIDX_DISCONNECTING, &us->dflags))
	{
		printk("Fail command during disconnect\n");
		srb->result = DID_NO_CONNECT << 16;
		done(srb);
		return 0;
	}

	/* enqueue the command and wake up the control thread */
	srb->scsi_done = done;
	us->srb = srb;
	complete(&us->cmnd_ready);

	return 0;
}

static DEF_SCSI_QCMD(queuecommand)

/***********************************************************************
 * Error handling functions
 ***********************************************************************/

/* Command timeout and abort */
//----- command_abort() ---------------------
static int command_abort(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);

	//printk("scsiglue --- command_abort\n");

	scsi_lock(us_to_host(us));
	if (us->srb != srb)
	{
		scsi_unlock(us_to_host(us));
		printk ("-- nothing to abort\n");
		return FAILED;
	}

	set_bit(US_FLIDX_TIMED_OUT, &us->dflags);
	if (!test_bit(US_FLIDX_RESETTING, &us->dflags))
	{
		set_bit(US_FLIDX_ABORTING, &us->dflags);
		usb_stor_stop_transport(us);
	}
	scsi_unlock(us_to_host(us));

	/* Wait for the aborted command to finish */
	wait_for_completion(&us->notify);
	return SUCCESS;
}

/* This invokes the transport reset mechanism to reset the state of the device */
//----- device_reset() ---------------------
static int device_reset(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);
	int result;

	//printk("scsiglue --- device_reset\n");

	/* lock the device pointers and do the reset */
	mutex_lock(&(us->dev_mutex));
	result = us->transport_reset(us);
	mutex_unlock(&us->dev_mutex);

	return result < 0 ? FAILED : SUCCESS;
}

//----- bus_reset() ---------------------
static int bus_reset(struct scsi_cmnd *srb)
{
	struct us_data *us = host_to_us(srb->device->host);
	int result;

	//printk("scsiglue --- bus_reset\n");
	result = usb_stor_port_reset(us);
	return result < 0 ? FAILED : SUCCESS;
}

//----- usb_stor_report_device_reset() ---------------------
void usb_stor_report_device_reset(struct us_data *us)
{
	int i;
	struct Scsi_Host *host = us_to_host(us);

	//printk("scsiglue --- usb_stor_report_device_reset\n");
	scsi_report_device_reset(host, 0, 0);
	if (us->fflags & US_FL_SCM_MULT_TARG)
	{
		for (i = 1; i < host->max_id; ++i)
			scsi_report_device_reset(host, 0, i);
	}
}

//----- usb_stor_report_bus_reset() ---------------------
void usb_stor_report_bus_reset(struct us_data *us)
{
	struct Scsi_Host *host = us_to_host(us);

	//printk("scsiglue --- usb_stor_report_bus_reset\n");
	scsi_lock(host);
	scsi_report_bus_reset(host, 0);
	scsi_unlock(host);
}

/***********************************************************************
 * /proc/scsi/ functions
 ***********************************************************************/

/* we use this macro to help us write into the buffer */
#undef SPRINTF
#define SPRINTF(args...) \
	do { if (pos < buffer+length) pos += sprintf(pos, ## args); } while (0)

//----- proc_info() ---------------------
static int proc_info (struct Scsi_Host *host, char *buffer, char **start, off_t offset, int length, int inout)
{
	struct us_data *us = host_to_us(host);
	char *pos = buffer;
	const char *string;

	//printk("scsiglue --- proc_info\n");
	if (inout)
		return length;

	/* print the controller name */
	SPRINTF("   Host scsi%d: usb-storage\n", host->host_no);

	/* print product, vendor, and serial number strings */
	if (us->pusb_dev->manufacturer)
		string = us->pusb_dev->manufacturer;
	else if (us->unusual_dev->vendorName)
		string = us->unusual_dev->vendorName;
	else
		string = "Unknown";
	SPRINTF("       Vendor: %s\n", string);
	if (us->pusb_dev->product)
		string = us->pusb_dev->product;
	else if (us->unusual_dev->productName)
		string = us->unusual_dev->productName;
	else
		string = "Unknown";
	SPRINTF("      Product: %s\n", string);
	if (us->pusb_dev->serial)
		string = us->pusb_dev->serial;
	else
		string = "None";
	SPRINTF("Serial Number: %s\n", string);

	/* show the protocol and transport */
	SPRINTF("     Protocol: %s\n", us->protocol_name);
	SPRINTF("    Transport: %s\n", us->transport_name);

	/* show the device flags */
	if (pos < buffer + length)
	{
		pos += sprintf(pos, "       Quirks:");

#define US_FLAG(name, value) \
	if (us->fflags & value) pos += sprintf(pos, " " #name);
US_DO_ALL_FLAGS
#undef US_FLAG

		*(pos++) = '\n';
	}

	/* Calculate start of next buffer, and return value. */
	*start = buffer + offset;

	if ((pos - buffer) < offset)
		return (0);
	else if ((pos - buffer - offset) < length)
		return (pos - buffer - offset);
	else
		return (length);
}

/***********************************************************************
 * Sysfs interface
 ***********************************************************************/

/* Output routine for the sysfs max_sectors file */
//----- show_max_sectors() ---------------------
static ssize_t show_max_sectors(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct scsi_device *sdev = to_scsi_device(dev);

	//printk("scsiglue --- ssize_t show_max_sectors\n");
	return sprintf(buf, "%u\n", queue_max_sectors(sdev->request_queue));
}

/* Input routine for the sysfs max_sectors file */
//----- store_max_sectors() ---------------------
static ssize_t store_max_sectors(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	struct scsi_device *sdev = to_scsi_device(dev);
	unsigned short ms;

	//printk("scsiglue --- ssize_t store_max_sectors\n");
	if (sscanf(buf, "%hu", &ms) > 0 && ms <= SCSI_DEFAULT_MAX_SECTORS)
	{
		blk_queue_max_hw_sectors(sdev->request_queue, ms);
		return strlen(buf);
	}
	return -EINVAL;	
}

static DEVICE_ATTR(max_sectors, S_IRUGO | S_IWUSR, show_max_sectors, store_max_sectors);
static struct device_attribute *sysfs_device_attr_list[] = {&dev_attr_max_sectors, NULL, };

/* this defines our host template, with which we'll allocate hosts */

//----- usb_stor_host_template() ---------------------
struct scsi_host_template usb_stor_host_template = {
	/* basic userland interface stuff */
	.name =				"eucr-storage",
	.proc_name =			"eucr-storage",
	.proc_info =			proc_info,
	.info =				host_info,

	/* command interface -- queued only */
	.queuecommand =			queuecommand,

	/* error and abort handlers */
	.eh_abort_handler =		command_abort,
	.eh_device_reset_handler =	device_reset,
	.eh_bus_reset_handler =		bus_reset,

	/* queue commands only, only one command per LUN */
	.can_queue =			1,
	.cmd_per_lun =			1,

	/* unknown initiator id */
	.this_id =			-1,

	.slave_alloc =			slave_alloc,
	.slave_configure =		slave_configure,

	/* lots of sg segments can be handled */
	.sg_tablesize =			SG_ALL,

	/* limit the total size of a transfer to 120 KB */
	.max_sectors =                  240,

	/* merge commands... this seems to help performance, but
	 * periodically someone should test to see which setting is more
	 * optimal.
	 */
	.use_clustering =		1,

	/* emulated HBA */
	.emulated =			1,

	/* we do our own delay after a device or bus reset */
	.skip_settle_delay =		1,

	/* sysfs device attributes */
	.sdev_attrs =			sysfs_device_attr_list,

	/* module management */
	.module =			THIS_MODULE
};

/* To Report "Illegal Request: Invalid Field in CDB */
unsigned char usb_stor_sense_invalidCDB[18] = {
	[0]	= 0x70,			    /* current error */
	[2]	= ILLEGAL_REQUEST,	    /* Illegal Request = 0x05 */
	[7]	= 0x0a,			    /* additional length */
	[12]	= 0x24			    /* Invalid Field in CDB */
};

/***********************************************************************
 * Scatter-gather transfer buffer access routines
 ***********************************************************************/

//----- usb_stor_access_xfer_buf() ---------------------
unsigned int usb_stor_access_xfer_buf(struct us_data *us, unsigned char *buffer,
	unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
	unsigned int *offset, enum xfer_buf_dir dir)
{
	unsigned int cnt;

	//printk("transport --- usb_stor_access_xfer_buf\n");
	struct scatterlist *sg = *sgptr;

	if (!sg)
		sg = scsi_sglist(srb);

	cnt = 0;
	while (cnt < buflen && sg)
	{
		struct page *page = sg_page(sg) + ((sg->offset + *offset) >> PAGE_SHIFT);
		unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
		unsigned int sglen = sg->length - *offset;

		if (sglen > buflen - cnt)
		{
			/* Transfer ends within this s-g entry */
			sglen = buflen - cnt;
			*offset += sglen;
		}
		else
		{
			/* Transfer continues to next s-g entry */
			*offset = 0;
			sg = sg_next(sg);
		}

		while (sglen > 0)
		{
			unsigned int plen = min(sglen, (unsigned int)PAGE_SIZE - poff);
			unsigned char *ptr = kmap(page);

			if (dir == TO_XFER_BUF)
				memcpy(ptr + poff, buffer + cnt, plen);
			else
				memcpy(buffer + cnt, ptr + poff, plen);
			kunmap(page);

			/* Start at the beginning of the next page */
			poff = 0;
			++page;
			cnt += plen;
			sglen -= plen;
		}
	}
	*sgptr = sg;

	/* Return the amount actually transferred */
	return cnt;
}

/* Store the contents of buffer into srb's transfer buffer and set the SCSI residue. */
//----- usb_stor_set_xfer_buf() ---------------------
void usb_stor_set_xfer_buf(struct us_data *us, unsigned char *buffer, unsigned int buflen, struct scsi_cmnd *srb,
	unsigned int dir)
{
	unsigned int offset = 0;
	struct scatterlist *sg = NULL;

	//printk("transport --- usb_stor_set_xfer_buf\n");
	// TO_XFER_BUF = 0, FROM_XFER_BUF = 1
	buflen = min(buflen, scsi_bufflen(srb));
	buflen = usb_stor_access_xfer_buf(us, buffer, buflen, srb, &sg, &offset, dir);
	if (buflen < scsi_bufflen(srb))
		scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
}