Archipelago » qemu

/*

 * SCSI Device emulation

 *

 * Copyright (c) 2006 CodeSourcery.

 * Based on code by Fabrice Bellard

 *

 * Written by Paul Brook

 * Modifications:

 *  2009-Dec-12 Artyom Tarasenko : implemented stamdard inquiry for the case

 *                                 when the allocation length of CDB is smaller

 *                                 than 36.

 *  2009-Oct-13 Artyom Tarasenko : implemented the block descriptor in the

 *                                 MODE SENSE response.

 *

 * This code is licenced under the LGPL.

 *

 * Note that this file only handles the SCSI architecture model and device

 * commands.  Emulation of interface/link layer protocols is handled by

 * the host adapter emulator.

 */

//#define DEBUG_SCSI

#ifdef DEBUG_SCSI

#define DPRINTF(fmt, ...) \

do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)

#else

#define DPRINTF(fmt, ...) do {} while(0)

#endif

#define BADF(fmt, ...) \

do { fprintf(stderr, "scsi-disk: " fmt , ## __VA_ARGS__); } while (0)

#include "qemu-common.h"

#include "qemu-error.h"

#include "scsi.h"

#include "scsi-defs.h"

#include "sysemu.h"

#include "blockdev.h"

#define SCSI_DMA_BUF_SIZE    131072

#define SCSI_MAX_INQUIRY_LEN 256

#define SCSI_REQ_STATUS_RETRY 0x01

typedef struct SCSIDiskState SCSIDiskState;

typedef struct SCSIDiskReq {

    SCSIRequest req;

    /* ??? We should probably keep track of whether the data transfer is

       a read or a write.  Currently we rely on the host getting it right.  */

    /* Both sector and sector_count are in terms of qemu 512 byte blocks.  */

    uint64_t sector;

    uint32_t sector_count;

    struct iovec iov;

    QEMUIOVector qiov;

    uint32_t status;

} SCSIDiskReq;

struct SCSIDiskState

{

    SCSIDevice qdev;

    BlockDriverState *bs;

    /* The qemu block layer uses a fixed 512 byte sector size.

       This is the number of 512 byte blocks in a single scsi sector.  */

    int cluster_size;

    uint64_t max_lba;

    QEMUBH *bh;

    char *version;

    char *serial;

};

static SCSIDiskReq *scsi_new_request(SCSIDevice *d, uint32_t tag, uint32_t lun)

{

    SCSIRequest *req;

    SCSIDiskReq *r;

    req = scsi_req_alloc(sizeof(SCSIDiskReq), d, tag, lun);

    r = DO_UPCAST(SCSIDiskReq, req, req);

    r->iov.iov_base = qemu_memalign(512, SCSI_DMA_BUF_SIZE);

    return r;

}

static void scsi_remove_request(SCSIDiskReq *r)

{

    qemu_vfree(r->iov.iov_base);

    scsi_req_free(&r->req);

}

static SCSIDiskReq *scsi_find_request(SCSIDiskState *s, uint32_t tag)

{

    return DO_UPCAST(SCSIDiskReq, req, scsi_req_find(&s->qdev, tag));

}

static void scsi_req_set_status(SCSIRequest *req, int status, int sense_code)

{

    req->status = status;

    scsi_dev_set_sense(req->dev, sense_code);

}

/* Helper function for command completion.  */

static void scsi_command_complete(SCSIDiskReq *r, int status, int sense)

{

    DPRINTF("Command complete tag=0x%x status=%d sense=%d\n",

            r->req.tag, status, sense);

    scsi_req_set_status(&r->req, status, sense);

    scsi_req_complete(&r->req);

    scsi_remove_request(r);

}

/* Cancel a pending data transfer.  */

static void scsi_cancel_io(SCSIDevice *d, uint32_t tag)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);

    SCSIDiskReq *r;

    DPRINTF("Cancel tag=0x%x\n", tag);

    r = scsi_find_request(s, tag);

    if (r) {

        if (r->req.aiocb)

            bdrv_aio_cancel(r->req.aiocb);

        r->req.aiocb = NULL;

        scsi_remove_request(r);

    }

}

static void scsi_read_complete(void * opaque, int ret)

{

    SCSIDiskReq *r = (SCSIDiskReq *)opaque;

    r->req.aiocb = NULL;

    if (ret) {

        DPRINTF("IO error\n");

        r->req.bus->complete(r->req.bus, SCSI_REASON_DATA, r->req.tag, 0);

        scsi_command_complete(r, CHECK_CONDITION, NO_SENSE);

        return;

    }

    DPRINTF("Data ready tag=0x%x len=%" PRId64 "\n", r->req.tag, r->iov.iov_len);

    r->req.bus->complete(r->req.bus, SCSI_REASON_DATA, r->req.tag, r->iov.iov_len);

}

/* Read more data from scsi device into buffer.  */

static void scsi_read_data(SCSIDevice *d, uint32_t tag)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);

    SCSIDiskReq *r;

    uint32_t n;

    r = scsi_find_request(s, tag);

    if (!r) {

        BADF("Bad read tag 0x%x\n", tag);

        /* ??? This is the wrong error.  */

        scsi_command_complete(r, CHECK_CONDITION, HARDWARE_ERROR);

        return;

    }

    if (r->sector_count == (uint32_t)-1) {

        DPRINTF("Read buf_len=%" PRId64 "\n", r->iov.iov_len);

        r->sector_count = 0;

        r->req.bus->complete(r->req.bus, SCSI_REASON_DATA, r->req.tag, r->iov.iov_len);

        return;

    }

    DPRINTF("Read sector_count=%d\n", r->sector_count);

    if (r->sector_count == 0) {

        scsi_command_complete(r, GOOD, NO_SENSE);

        return;

    }

    n = r->sector_count;

    if (n > SCSI_DMA_BUF_SIZE / 512)

        n = SCSI_DMA_BUF_SIZE / 512;

    r->iov.iov_len = n * 512;

    qemu_iovec_init_external(&r->qiov, &r->iov, 1);

    r->req.aiocb = bdrv_aio_readv(s->bs, r->sector, &r->qiov, n,

                              scsi_read_complete, r);

    if (r->req.aiocb == NULL)

        scsi_command_complete(r, CHECK_CONDITION, HARDWARE_ERROR);

    r->sector += n;

    r->sector_count -= n;

}

static int scsi_handle_write_error(SCSIDiskReq *r, int error)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);

    BlockErrorAction action = bdrv_get_on_error(s->bs, 0);

    if (action == BLOCK_ERR_IGNORE) {

        bdrv_mon_event(s->bs, BDRV_ACTION_IGNORE, 0);

        return 0;

    }

    if ((error == ENOSPC && action == BLOCK_ERR_STOP_ENOSPC)

            || action == BLOCK_ERR_STOP_ANY) {

        r->status |= SCSI_REQ_STATUS_RETRY;

        bdrv_mon_event(s->bs, BDRV_ACTION_STOP, 0);

        vm_stop(0);

    } else {

        scsi_command_complete(r, CHECK_CONDITION,

                HARDWARE_ERROR);

        bdrv_mon_event(s->bs, BDRV_ACTION_REPORT, 0);

    }

    return 1;

}

static void scsi_write_complete(void * opaque, int ret)

{

    SCSIDiskReq *r = (SCSIDiskReq *)opaque;

    uint32_t len;

    uint32_t n;

    r->req.aiocb = NULL;

    if (ret) {

        if (scsi_handle_write_error(r, -ret))

            return;

    }

    n = r->iov.iov_len / 512;

    r->sector += n;

    r->sector_count -= n;

    if (r->sector_count == 0) {

        scsi_command_complete(r, GOOD, NO_SENSE);

    } else {

        len = r->sector_count * 512;

        if (len > SCSI_DMA_BUF_SIZE) {

            len = SCSI_DMA_BUF_SIZE;

        }

        r->iov.iov_len = len;

        DPRINTF("Write complete tag=0x%x more=%d\n", r->req.tag, len);

        r->req.bus->complete(r->req.bus, SCSI_REASON_DATA, r->req.tag, len);

    }

}

static void scsi_write_request(SCSIDiskReq *r)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);

    uint32_t n;

    n = r->iov.iov_len / 512;

    if (n) {

        qemu_iovec_init_external(&r->qiov, &r->iov, 1);

        r->req.aiocb = bdrv_aio_writev(s->bs, r->sector, &r->qiov, n,

                                   scsi_write_complete, r);

        if (r->req.aiocb == NULL)

            scsi_command_complete(r, CHECK_CONDITION,

                                  HARDWARE_ERROR);

    } else {

        /* Invoke completion routine to fetch data from host.  */

        scsi_write_complete(r, 0);

    }

}

/* Write data to a scsi device.  Returns nonzero on failure.

   The transfer may complete asynchronously.  */

static int scsi_write_data(SCSIDevice *d, uint32_t tag)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);

    SCSIDiskReq *r;

    DPRINTF("Write data tag=0x%x\n", tag);

    r = scsi_find_request(s, tag);

    if (!r) {

        BADF("Bad write tag 0x%x\n", tag);

        scsi_command_complete(r, CHECK_CONDITION, HARDWARE_ERROR);

        return 1;

    }

    if (r->req.aiocb)

        BADF("Data transfer already in progress\n");

    scsi_write_request(r);

    return 0;

}

static void scsi_dma_restart_bh(void *opaque)

{

    SCSIDiskState *s = opaque;

    SCSIRequest *req;

    SCSIDiskReq *r;

    qemu_bh_delete(s->bh);

    s->bh = NULL;

    QTAILQ_FOREACH(req, &s->qdev.requests, next) {

        r = DO_UPCAST(SCSIDiskReq, req, req);

        if (r->status & SCSI_REQ_STATUS_RETRY) {

            r->status &= ~SCSI_REQ_STATUS_RETRY;

            scsi_write_request(r); 

        }

    }

}

static void scsi_dma_restart_cb(void *opaque, int running, int reason)

{

    SCSIDiskState *s = opaque;

    if (!running)

        return;

    if (!s->bh) {

        s->bh = qemu_bh_new(scsi_dma_restart_bh, s);

        qemu_bh_schedule(s->bh);

    }

}

/* Return a pointer to the data buffer.  */

static uint8_t *scsi_get_buf(SCSIDevice *d, uint32_t tag)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, d);

    SCSIDiskReq *r;

    r = scsi_find_request(s, tag);

    if (!r) {

        BADF("Bad buffer tag 0x%x\n", tag);

        return NULL;

    }

    return (uint8_t *)r->iov.iov_base;

}

static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);

    int buflen = 0;

    if (req->cmd.buf[1] & 0x2) {

        /* Command support data - optional, not implemented */

        BADF("optional INQUIRY command support request not implemented\n");

        return -1;

    }

    if (req->cmd.buf[1] & 0x1) {

        /* Vital product data */

        uint8_t page_code = req->cmd.buf[2];

        if (req->cmd.xfer < 4) {

            BADF("Error: Inquiry (EVPD[%02X]) buffer size %zd is "

                 "less than 4\n", page_code, req->cmd.xfer);

            return -1;

        }

        if (bdrv_get_type_hint(s->bs) == BDRV_TYPE_CDROM) {

            outbuf[buflen++] = 5;

        } else {

            outbuf[buflen++] = 0;

        }

        outbuf[buflen++] = page_code ; // this page

        outbuf[buflen++] = 0x00;

        switch (page_code) {

        case 0x00: /* Supported page codes, mandatory */

            DPRINTF("Inquiry EVPD[Supported pages] "

                    "buffer size %zd\n", req->cmd.xfer);

            outbuf[buflen++] = 4;    // number of pages

            outbuf[buflen++] = 0x00; // list of supported pages (this page)

            outbuf[buflen++] = 0x80; // unit serial number

            outbuf[buflen++] = 0x83; // device identification

            outbuf[buflen++] = 0xb0; // block device characteristics

            break;

        case 0x80: /* Device serial number, optional */

        {

            int l = strlen(s->serial);

            if (l > req->cmd.xfer)

                l = req->cmd.xfer;

            if (l > 20)

                l = 20;

            DPRINTF("Inquiry EVPD[Serial number] "

                    "buffer size %zd\n", req->cmd.xfer);

            outbuf[buflen++] = l;

            memcpy(outbuf+buflen, s->serial, l);

            buflen += l;

            break;

        }

        case 0x83: /* Device identification page, mandatory */

        {

            int max_len = 255 - 8;

            int id_len = strlen(bdrv_get_device_name(s->bs));

            if (id_len > max_len)

                id_len = max_len;

            DPRINTF("Inquiry EVPD[Device identification] "

                    "buffer size %zd\n", req->cmd.xfer);

            outbuf[buflen++] = 3 + id_len;

            outbuf[buflen++] = 0x2; // ASCII

            outbuf[buflen++] = 0;   // not officially assigned

            outbuf[buflen++] = 0;   // reserved

            outbuf[buflen++] = id_len; // length of data following

            memcpy(outbuf+buflen, bdrv_get_device_name(s->bs), id_len);

            buflen += id_len;

            break;

        }

        case 0xb0: /* block device characteristics */

        {

            unsigned int min_io_size =

                    s->qdev.conf.min_io_size / s->qdev.blocksize;

            unsigned int opt_io_size =

                    s->qdev.conf.opt_io_size / s->qdev.blocksize;

            /* required VPD size with unmap support */

            outbuf[3] = buflen = 0x3c;

            memset(outbuf + 4, 0, buflen - 4);

            /* optimal transfer length granularity */

            outbuf[6] = (min_io_size >> 8) & 0xff;

            outbuf[7] = min_io_size & 0xff;

            /* optimal transfer length */

            outbuf[12] = (opt_io_size >> 24) & 0xff;

            outbuf[13] = (opt_io_size >> 16) & 0xff;

            outbuf[14] = (opt_io_size >> 8) & 0xff;

            outbuf[15] = opt_io_size & 0xff;

            break;

        }

        default:

            BADF("Error: unsupported Inquiry (EVPD[%02X]) "

                 "buffer size %zd\n", page_code, req->cmd.xfer);

            return -1;

        }

        /* done with EVPD */

        return buflen;

    }

    /* Standard INQUIRY data */

    if (req->cmd.buf[2] != 0) {

        BADF("Error: Inquiry (STANDARD) page or code "

             "is non-zero [%02X]\n", req->cmd.buf[2]);

        return -1;

    }

    /* PAGE CODE == 0 */

    if (req->cmd.xfer < 5) {

        BADF("Error: Inquiry (STANDARD) buffer size %zd "

             "is less than 5\n", req->cmd.xfer);

        return -1;

    }

    buflen = req->cmd.xfer;

    if (buflen > SCSI_MAX_INQUIRY_LEN)

        buflen = SCSI_MAX_INQUIRY_LEN;

    memset(outbuf, 0, buflen);

    if (req->lun || req->cmd.buf[1] >> 5) {

        outbuf[0] = 0x7f;        /* LUN not supported */

        return buflen;

    }

    if (bdrv_get_type_hint(s->bs) == BDRV_TYPE_CDROM) {

        outbuf[0] = 5;

        outbuf[1] = 0x80;

        memcpy(&outbuf[16], "QEMU CD-ROM     ", 16);

    } else {

        outbuf[0] = 0;

        memcpy(&outbuf[16], "QEMU HARDDISK   ", 16);

    }

    memcpy(&outbuf[8], "QEMU    ", 8);

    memset(&outbuf[32], 0, 4);

    memcpy(&outbuf[32], s->version, MIN(4, strlen(s->version)));

    /*

     * We claim conformance to SPC-3, which is required for guests

     * to ask for modern features like READ CAPACITY(16) or the

     * block characteristics VPD page by default.  Not all of SPC-3

     * is actually implemented, but we're good enough.

     */

    outbuf[2] = 5;

    outbuf[3] = 2; /* Format 2 */

    if (buflen > 36) {

        outbuf[4] = buflen - 5; /* Additional Length = (Len - 1) - 4 */

    } else {

        /* If the allocation length of CDB is too small,

               the additional length is not adjusted */

        outbuf[4] = 36 - 5;

    }

    /* Sync data transfer and TCQ.  */

    outbuf[7] = 0x10 | (req->bus->tcq ? 0x02 : 0);

    return buflen;

}

static int mode_sense_page(SCSIRequest *req, int page, uint8_t *p)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);

    BlockDriverState *bdrv = s->bs;

    int cylinders, heads, secs;

    switch (page) {

    case 4: /* Rigid disk device geometry page. */

        p[0] = 4;

        p[1] = 0x16;

        /* if a geometry hint is available, use it */

        bdrv_get_geometry_hint(bdrv, &cylinders, &heads, &secs);

        p[2] = (cylinders >> 16) & 0xff;

        p[3] = (cylinders >> 8) & 0xff;

        p[4] = cylinders & 0xff;

        p[5] = heads & 0xff;

        /* Write precomp start cylinder, disabled */

        p[6] = (cylinders >> 16) & 0xff;

        p[7] = (cylinders >> 8) & 0xff;

        p[8] = cylinders & 0xff;

        /* Reduced current start cylinder, disabled */

        p[9] = (cylinders >> 16) & 0xff;

        p[10] = (cylinders >> 8) & 0xff;

        p[11] = cylinders & 0xff;

        /* Device step rate [ns], 200ns */

        p[12] = 0;

        p[13] = 200;

        /* Landing zone cylinder */

        p[14] = 0xff;

        p[15] =  0xff;

        p[16] = 0xff;

        /* Medium rotation rate [rpm], 5400 rpm */

        p[20] = (5400 >> 8) & 0xff;

        p[21] = 5400 & 0xff;

        return 0x16;

    case 5: /* Flexible disk device geometry page. */

        p[0] = 5;

        p[1] = 0x1e;

        /* Transfer rate [kbit/s], 5Mbit/s */

        p[2] = 5000 >> 8;

        p[3] = 5000 & 0xff;

        /* if a geometry hint is available, use it */

        bdrv_get_geometry_hint(bdrv, &cylinders, &heads, &secs);

        p[4] = heads & 0xff;

        p[5] = secs & 0xff;

        p[6] = s->cluster_size * 2;

        p[8] = (cylinders >> 8) & 0xff;

        p[9] = cylinders & 0xff;

        /* Write precomp start cylinder, disabled */

        p[10] = (cylinders >> 8) & 0xff;

        p[11] = cylinders & 0xff;

        /* Reduced current start cylinder, disabled */

        p[12] = (cylinders >> 8) & 0xff;

        p[13] = cylinders & 0xff;

        /* Device step rate [100us], 100us */

        p[14] = 0;

        p[15] = 1;

        /* Device step pulse width [us], 1us */

        p[16] = 1;

        /* Device head settle delay [100us], 100us */

        p[17] = 0;

        p[18] = 1;

        /* Motor on delay [0.1s], 0.1s */

        p[19] = 1;

        /* Motor off delay [0.1s], 0.1s */

        p[20] = 1;

        /* Medium rotation rate [rpm], 5400 rpm */

        p[28] = (5400 >> 8) & 0xff;

        p[29] = 5400 & 0xff;

        return 0x1e;

    case 8: /* Caching page.  */

        p[0] = 8;

        p[1] = 0x12;

        if (bdrv_enable_write_cache(s->bs)) {

            p[2] = 4; /* WCE */

        }

        return 20;

    case 0x2a: /* CD Capabilities and Mechanical Status page. */

        if (bdrv_get_type_hint(bdrv) != BDRV_TYPE_CDROM)

            return 0;

        p[0] = 0x2a;

        p[1] = 0x14;

        p[2] = 3; // CD-R & CD-RW read

        p[3] = 0; // Writing not supported

        p[4] = 0x7f; /* Audio, composite, digital out,

                        mode 2 form 1&2, multi session */

        p[5] = 0xff; /* CD DA, DA accurate, RW supported,

                        RW corrected, C2 errors, ISRC,

                        UPC, Bar code */

        p[6] = 0x2d | (bdrv_is_locked(s->bs)? 2 : 0);

        /* Locking supported, jumper present, eject, tray */

        p[7] = 0; /* no volume & mute control, no

                     changer */

        p[8] = (50 * 176) >> 8; // 50x read speed

        p[9] = (50 * 176) & 0xff;

        p[10] = 0 >> 8; // No volume

        p[11] = 0 & 0xff;

        p[12] = 2048 >> 8; // 2M buffer

        p[13] = 2048 & 0xff;

        p[14] = (16 * 176) >> 8; // 16x read speed current

        p[15] = (16 * 176) & 0xff;

        p[18] = (16 * 176) >> 8; // 16x write speed

        p[19] = (16 * 176) & 0xff;

        p[20] = (16 * 176) >> 8; // 16x write speed current

        p[21] = (16 * 176) & 0xff;

        return 22;

    default:

        return 0;

    }

}

static int scsi_disk_emulate_mode_sense(SCSIRequest *req, uint8_t *outbuf)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);

    uint64_t nb_sectors;

    int page, dbd, buflen;

    uint8_t *p;

    dbd = req->cmd.buf[1]  & 0x8;

    page = req->cmd.buf[2] & 0x3f;

    DPRINTF("Mode Sense (page %d, len %zd)\n", page, req->cmd.xfer);

    memset(outbuf, 0, req->cmd.xfer);

    p = outbuf;

    p[1] = 0; /* Default media type.  */

    p[3] = 0; /* Block descriptor length.  */

    if (bdrv_is_read_only(s->bs)) {

        p[2] = 0x80; /* Readonly.  */

    }

    p += 4;

    bdrv_get_geometry(s->bs, &nb_sectors);

    if ((~dbd) & nb_sectors) {

        outbuf[3] = 8; /* Block descriptor length  */

        nb_sectors /= s->cluster_size;

        nb_sectors--;

        if (nb_sectors > 0xffffff)

            nb_sectors = 0xffffff;

        p[0] = 0; /* media density code */

        p[1] = (nb_sectors >> 16) & 0xff;

        p[2] = (nb_sectors >> 8) & 0xff;

        p[3] = nb_sectors & 0xff;

        p[4] = 0; /* reserved */

        p[5] = 0; /* bytes 5-7 are the sector size in bytes */

        p[6] = s->cluster_size * 2;

        p[7] = 0;

        p += 8;

    }

    switch (page) {

    case 0x04:

    case 0x05:

    case 0x08:

    case 0x2a:

        p += mode_sense_page(req, page, p);

        break;

    case 0x3f:

        p += mode_sense_page(req, 0x08, p);

        p += mode_sense_page(req, 0x2a, p);

        break;

    }

    buflen = p - outbuf;

    outbuf[0] = buflen - 4;

    if (buflen > req->cmd.xfer)

        buflen = req->cmd.xfer;

    return buflen;

}

static int scsi_disk_emulate_read_toc(SCSIRequest *req, uint8_t *outbuf)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);

    int start_track, format, msf, toclen;

    uint64_t nb_sectors;

    msf = req->cmd.buf[1] & 2;

    format = req->cmd.buf[2] & 0xf;

    start_track = req->cmd.buf[6];

    bdrv_get_geometry(s->bs, &nb_sectors);

    DPRINTF("Read TOC (track %d format %d msf %d)\n", start_track, format, msf >> 1);

    nb_sectors /= s->cluster_size;

    switch (format) {

    case 0:

        toclen = cdrom_read_toc(nb_sectors, outbuf, msf, start_track);

        break;

    case 1:

        /* multi session : only a single session defined */

        toclen = 12;

        memset(outbuf, 0, 12);

        outbuf[1] = 0x0a;

        outbuf[2] = 0x01;

        outbuf[3] = 0x01;

        break;

    case 2:

        toclen = cdrom_read_toc_raw(nb_sectors, outbuf, msf, start_track);

        break;

    default:

        return -1;

    }

    if (toclen > req->cmd.xfer)

        toclen = req->cmd.xfer;

    return toclen;

}

static int scsi_disk_emulate_command(SCSIRequest *req, uint8_t *outbuf)

{

    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);

    uint64_t nb_sectors;

    int buflen = 0;

    switch (req->cmd.buf[0]) {

    case TEST_UNIT_READY:

        if (!bdrv_is_inserted(s->bs))

            goto not_ready;

        break;

    case REQUEST_SENSE:

        if (req->cmd.xfer < 4)

            goto illegal_request;

        memset(outbuf, 0, 4);

        buflen = 4;

        if (req->dev->sense.key == NOT_READY && req->cmd.xfer >= 18) {

            memset(outbuf, 0, 18);

            buflen = 18;

            outbuf[7] = 10;

            /* asc 0x3a, ascq 0: Medium not present */

            outbuf[12] = 0x3a;

            outbuf[13] = 0;

        }

        outbuf[0] = 0xf0;

        outbuf[1] = 0;

        outbuf[2] = req->dev->sense.key;

        scsi_dev_clear_sense(req->dev);

        break;

    case INQUIRY:

        buflen = scsi_disk_emulate_inquiry(req, outbuf);

        if (buflen < 0)

            goto illegal_request;

        break;

    case MODE_SENSE:

    case MODE_SENSE_10:

        buflen = scsi_disk_emulate_mode_sense(req, outbuf);

        if (buflen < 0)

            goto illegal_request;

        break;

    case READ_TOC:

        buflen = scsi_disk_emulate_read_toc(req, outbuf);

        if (buflen < 0)

            goto illegal_request;

        break;

    case RESERVE:

        if (req->cmd.buf[1] & 1)

            goto illegal_request;

        break;

    case RESERVE_10:

        if (req->cmd.buf[1] & 3)

            goto illegal_request;

        break;

    case RELEASE:

        if (req->cmd.buf[1] & 1)

            goto illegal_request;

        break;

    case RELEASE_10:

        if (req->cmd.buf[1] & 3)

            goto illegal_request;

        break;

    case START_STOP:

        if (bdrv_get_type_hint(s->bs) == BDRV_TYPE_CDROM && (req->cmd.buf[4] & 2)) {

            /* load/eject medium */

            bdrv_eject(s->bs, !(req->cmd.buf[4] & 1));

        }

        break;

    case ALLOW_MEDIUM_REMOVAL:

        bdrv_set_locked(s->bs, req->cmd.buf[4] & 1);

        break;

    case READ_CAPACITY:

        /* The normal LEN field for this command is zero.  */

        memset(outbuf, 0, 8);

        bdrv_get_geometry(s->bs, &nb_sectors);

        if (!nb_sectors)

            goto not_ready;

        nb_sectors /= s->cluster_size;

        /* Returned value is the address of the last sector.  */

        nb_sectors--;

        /* Remember the new size for read/write sanity checking. */

        s->max_lba = nb_sectors;

        /* Clip to 2TB, instead of returning capacity modulo 2TB. */

        if (nb_sectors > UINT32_MAX)

            nb_sectors = UINT32_MAX;

        outbuf[0] = (nb_sectors >> 24) & 0xff;

        outbuf[1] = (nb_sectors >> 16) & 0xff;

        outbuf[2] = (nb_sectors >> 8) & 0xff;

        outbuf[3] = nb_sectors & 0xff;

        outbuf[4] = 0;

        outbuf[5] = 0;

        outbuf[6] = s->cluster_size * 2;

        outbuf[7] = 0;

        buflen = 8;

        break;

    case SYNCHRONIZE_CACHE:

        bdrv_flush(s->bs);

        break;

    case GET_CONFIGURATION:

        memset(outbuf, 0, 8);

        /* ??? This should probably return much more information.  For now

           just return the basic header indicating the CD-ROM profile.  */

        outbuf[7] = 8; // CD-ROM

        buflen = 8;

        break;

    case SERVICE_ACTION_IN:

        /* Service Action In subcommands. */

        if ((req->cmd.buf[1] & 31) == 0x10) {

            DPRINTF("SAI READ CAPACITY(16)\n");

            memset(outbuf, 0, req->cmd.xfer);

            bdrv_get_geometry(s->bs, &nb_sectors);

            if (!nb_sectors)

                goto not_ready;

            nb_sectors /= s->cluster_size;

            /* Returned value is the address of the last sector.  */

            nb_sectors--;

            /* Remember the new size for read/write sanity checking. */

            s->max_lba = nb_sectors;

            outbuf[0] = (nb_sectors >> 56) & 0xff;

            outbuf[1] = (nb_sectors >> 48) & 0xff;

            outbuf[2] = (nb_sectors >> 40) & 0xff;

            outbuf[3] = (nb_sectors >> 32) & 0xff;

            outbuf[4] = (nb_sectors >> 24) & 0xff;

            outbuf[5] = (nb_sectors >> 16) & 0xff;

            outbuf[6] = (nb_sectors >> 8) & 0xff;

            outbuf[7] = nb_sectors & 0xff;

            outbuf[8] = 0;

            outbuf[9] = 0;

            outbuf[10] = s->cluster_size * 2;

            outbuf[11] = 0;

            outbuf[12] = 0;

            outbuf[13] = get_physical_block_exp(&s->qdev.conf);

            /* Protection, exponent and lowest lba field left blank. */

            buflen = req->cmd.xfer;

            break;

        }

        DPRINTF("Unsupported Service Action In\n");

        goto illegal_request;

    case REPORT_LUNS:

        if (req->cmd.xfer < 16)

            goto illegal_request;

        memset(outbuf, 0, 16);

        outbuf[3] = 8;

        buflen = 16;

        break;

    case VERIFY:

        break;

    default:

        goto illegal_request;

    }

    scsi_req_set_status(req, GOOD, NO_SENSE);

    return buflen;

not_ready:

    scsi_req_set_status(req, CHECK_CONDITION, NOT_READY);

    return 0;

illegal_request:

    scsi_req_set_status(req, CHECK_CONDITION, ILLEGAL_REQUEST);

    return 0;

}