#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);
}