sd.c

/*
 * SD Memory Card emulation as defined in the "SD Memory Card Physical
 * layer specification, Version 1.10."
 *
 * Copyright (c) 2006 Andrzej Zaborowski  <balrog@zabor.org>
 * Copyright (c) 2007 CodeSourcery
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "hw.h"
#include "block.h"
#include "sd.h"

//#define DEBUG_SD 1

#ifdef DEBUG_SD
#define DPRINTF(fmt, ...) \
do { fprintf(stderr, "SD: " fmt , ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) do {} while(0)
#endif

typedef enum {
    sd_r0 = 0,    /* no response */
    sd_r1,        /* normal response command */
    sd_r2_i,      /* CID register */
    sd_r2_s,      /* CSD register */
    sd_r3,        /* OCR register */
    sd_r6 = 6,    /* Published RCA response */
    sd_r7,        /* Operating voltage */
    sd_r1b = -1,
} sd_rsp_type_t;

struct SDState {
    enum {
        sd_inactive,
        sd_card_identification_mode,
        sd_data_transfer_mode,
    } mode;
    enum {
        sd_inactive_state = -1,
        sd_idle_state = 0,
        sd_ready_state,
        sd_identification_state,
        sd_standby_state,
        sd_transfer_state,
        sd_sendingdata_state,
        sd_receivingdata_state,
        sd_programming_state,
        sd_disconnect_state,
    } state;
    uint32_t ocr;
    uint8_t scr[8];
    uint8_t cid[16];
    uint8_t csd[16];
    uint16_t rca;
    uint32_t card_status;
    uint8_t sd_status[64];
    uint32_t vhs;
    int wp_switch;
    int *wp_groups;
    uint64_t size;
    int blk_len;
    uint32_t erase_start;
    uint32_t erase_end;
    uint8_t pwd[16];
    int pwd_len;
    int function_group[6];

    int spi;
    int current_cmd;
    int blk_written;
    uint64_t data_start;
    uint32_t data_offset;
    uint8_t data[512];
    qemu_irq readonly_cb;
    qemu_irq inserted_cb;
    BlockDriverState *bdrv;
    uint8_t *buf;

    int enable;
};

static void sd_set_status(SDState *sd)
{
    switch (sd->state) {
    case sd_inactive_state:
        sd->mode = sd_inactive;
        break;

    case sd_idle_state:
    case sd_ready_state:
    case sd_identification_state:
        sd->mode = sd_card_identification_mode;
        break;

    case sd_standby_state:
    case sd_transfer_state:
    case sd_sendingdata_state:
    case sd_receivingdata_state:
    case sd_programming_state:
    case sd_disconnect_state:
        sd->mode = sd_data_transfer_mode;
        break;
    }

    sd->card_status &= ~CURRENT_STATE;
    sd->card_status |= sd->state << 9;
}

static const sd_cmd_type_t sd_cmd_type[64] = {
    sd_bc,   sd_none, sd_bcr,  sd_bcr,  sd_none, sd_none, sd_none, sd_ac,
    sd_bcr,  sd_ac,   sd_ac,   sd_adtc, sd_ac,   sd_ac,   sd_none, sd_ac,
    sd_ac,   sd_adtc, sd_adtc, sd_none, sd_none, sd_none, sd_none, sd_none,
    sd_adtc, sd_adtc, sd_adtc, sd_adtc, sd_ac,   sd_ac,   sd_adtc, sd_none,
    sd_ac,   sd_ac,   sd_none, sd_none, sd_none, sd_none, sd_ac,   sd_none,
    sd_none, sd_none, sd_bc,   sd_none, sd_none, sd_none, sd_none, sd_none,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_ac,
    sd_adtc, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none,
};

static const sd_cmd_type_t sd_acmd_type[64] = {
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_ac,   sd_none,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_adtc, sd_none, sd_none,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_adtc, sd_ac,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none,
    sd_none, sd_bcr,  sd_ac,   sd_none, sd_none, sd_none, sd_none, sd_none,
    sd_none, sd_none, sd_none, sd_adtc, sd_none, sd_none, sd_none, sd_none,
    sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none, sd_none,
};

static const int sd_cmd_class[64] = {
    0,  0,  0,  0,  0,  9, 10,  0,  0,  0,  0,  1,  0,  0,  0,  0,
    2,  2,  2,  2,  3,  3,  3,  3,  4,  4,  4,  4,  6,  6,  6,  6,
    5,  5, 10, 10, 10, 10,  5,  9,  9,  9,  7,  7,  7,  7,  7,  7,
    7,  7, 10,  7,  9,  9,  9,  8,  8, 10,  8,  8,  8,  8,  8,  8,
};

static uint8_t sd_crc7(void *message, size_t width)
{
    int i, bit;
    uint8_t shift_reg = 0x00;
    uint8_t *msg = (uint8_t *) message;

    for (i = 0; i < width; i ++, msg ++)
        for (bit = 7; bit >= 0; bit --) {
            shift_reg <<= 1;
            if ((shift_reg >> 7) ^ ((*msg >> bit) & 1))
                shift_reg ^= 0x89;
        }

    return shift_reg;
}

static uint16_t sd_crc16(void *message, size_t width)
{
    int i, bit;
    uint16_t shift_reg = 0x0000;
    uint16_t *msg = (uint16_t *) message;
    width <<= 1;

    for (i = 0; i < width; i ++, msg ++)
        for (bit = 15; bit >= 0; bit --) {
            shift_reg <<= 1;
            if ((shift_reg >> 15) ^ ((*msg >> bit) & 1))
                shift_reg ^= 0x1011;
        }

    return shift_reg;
}

static void sd_set_ocr(SDState *sd)
{
    /* All voltages OK, card power-up OK, Standard Capacity SD Memory Card */
    sd->ocr = 0x80ffff00;
}

static void sd_set_scr(SDState *sd)
{
    sd->scr[0] = 0x00;		/* SCR Structure */
    sd->scr[1] = 0x2f;		/* SD Security Support */
    sd->scr[2] = 0x00;
    sd->scr[3] = 0x00;
    sd->scr[4] = 0x00;
    sd->scr[5] = 0x00;
    sd->scr[6] = 0x00;
    sd->scr[7] = 0x00;
}

#define MID	0xaa
#define OID	"XY"
#define PNM	"QEMU!"
#define PRV	0x01
#define MDT_YR	2006
#define MDT_MON	2

static void sd_set_cid(SDState *sd)
{
    sd->cid[0] = MID;		/* Fake card manufacturer ID (MID) */
    sd->cid[1] = OID[0];	/* OEM/Application ID (OID) */
    sd->cid[2] = OID[1];
    sd->cid[3] = PNM[0];	/* Fake product name (PNM) */
    sd->cid[4] = PNM[1];
    sd->cid[5] = PNM[2];
    sd->cid[6] = PNM[3];
    sd->cid[7] = PNM[4];
    sd->cid[8] = PRV;		/* Fake product revision (PRV) */
    sd->cid[9] = 0xde;		/* Fake serial number (PSN) */
    sd->cid[10] = 0xad;
    sd->cid[11] = 0xbe;
    sd->cid[12] = 0xef;
    sd->cid[13] = 0x00 |	/* Manufacture date (MDT) */
        ((MDT_YR - 2000) / 10);
    sd->cid[14] = ((MDT_YR % 10) << 4) | MDT_MON;
    sd->cid[15] = (sd_crc7(sd->cid, 15) << 1) | 1;
}

#define HWBLOCK_SHIFT	9			/* 512 bytes */
#define SECTOR_SHIFT	5			/* 16 kilobytes */
#define WPGROUP_SHIFT	7			/* 2 megs */
#define CMULT_SHIFT	9			/* 512 times HWBLOCK_SIZE */
#define WPGROUP_SIZE	(1 << (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT))

static const uint8_t sd_csd_rw_mask[16] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xfc, 0xfe,
};

static void sd_set_csd(SDState *sd, uint64_t size)
{
    uint32_t csize = (size >> (CMULT_SHIFT + HWBLOCK_SHIFT)) - 1;
    uint32_t sectsize = (1 << (SECTOR_SHIFT + 1)) - 1;
    uint32_t wpsize = (1 << (WPGROUP_SHIFT + 1)) - 1;

    if (size <= 0x40000000) {	/* Standard Capacity SD */
        sd->csd[0] = 0x00;	/* CSD structure */
        sd->csd[1] = 0x26;	/* Data read access-time-1 */
        sd->csd[2] = 0x00;	/* Data read access-time-2 */
        sd->csd[3] = 0x5a;	/* Max. data transfer rate */
        sd->csd[4] = 0x5f;	/* Card Command Classes */
        sd->csd[5] = 0x50 |	/* Max. read data block length */
            HWBLOCK_SHIFT;
        sd->csd[6] = 0xe0 |	/* Partial block for read allowed */
            ((csize >> 10) & 0x03);
        sd->csd[7] = 0x00 |	/* Device size */
            ((csize >> 2) & 0xff);
        sd->csd[8] = 0x3f |	/* Max. read current */
            ((csize << 6) & 0xc0);
        sd->csd[9] = 0xfc |	/* Max. write current */
            ((CMULT_SHIFT - 2) >> 1);
        sd->csd[10] = 0x40 |	/* Erase sector size */
            (((CMULT_SHIFT - 2) << 7) & 0x80) | (sectsize >> 1);
        sd->csd[11] = 0x00 |	/* Write protect group size */
            ((sectsize << 7) & 0x80) | wpsize;
        sd->csd[12] = 0x90 |	/* Write speed factor */
            (HWBLOCK_SHIFT >> 2);
        sd->csd[13] = 0x20 |	/* Max. write data block length */
            ((HWBLOCK_SHIFT << 6) & 0xc0);
        sd->csd[14] = 0x00;	/* File format group */
        sd->csd[15] = (sd_crc7(sd->csd, 15) << 1) | 1;
    } else {			/* SDHC */
        size /= 512 * 1024;
        size -= 1;
        sd->csd[0] = 0x40;
        sd->csd[1] = 0x0e;
        sd->csd[2] = 0x00;
        sd->csd[3] = 0x32;
        sd->csd[4] = 0x5b;
        sd->csd[5] = 0x59;
        sd->csd[6] = 0x00;
        sd->csd[7] = (size >> 16) & 0xff;
        sd->csd[8] = (size >> 8) & 0xff;
        sd->csd[9] = (size & 0xff);
        sd->csd[10] = 0x7f;
        sd->csd[11] = 0x80;
        sd->csd[12] = 0x0a;
        sd->csd[13] = 0x40;
        sd->csd[14] = 0x00;
        sd->csd[15] = 0x00;
        sd->ocr |= 1 << 30;	/* High Capacity SD Memort Card */
    }
}

static void sd_set_rca(SDState *sd)
{
    sd->rca += 0x4567;
}

#define CARD_STATUS_A	0x02004100
#define CARD_STATUS_B	0x00c01e00
#define CARD_STATUS_C	0xfd39a028

static void sd_set_cardstatus(SDState *sd)
{
    sd->card_status = 0x00000100;
}

static void sd_set_sdstatus(SDState *sd)
{
    memset(sd->sd_status, 0, 64);
}

static int sd_req_crc_validate(SDRequest *req)
{
    uint8_t buffer[5];
    buffer[0] = 0x40 | req->cmd;
    buffer[1] = (req->arg >> 24) & 0xff;
    buffer[2] = (req->arg >> 16) & 0xff;
    buffer[3] = (req->arg >> 8) & 0xff;
    buffer[4] = (req->arg >> 0) & 0xff;
    return 0;
    return sd_crc7(buffer, 5) != req->crc;	/* TODO */
}

static void sd_response_r1_make(SDState *sd,
                                uint8_t *response, uint32_t last_status)
{
    uint32_t mask = CARD_STATUS_B ^ ILLEGAL_COMMAND;
    uint32_t status;

    status = (sd->card_status & ~mask) | (last_status & mask);
    sd->card_status &= ~CARD_STATUS_C | APP_CMD;

    response[0] = (status >> 24) & 0xff;
    response[1] = (status >> 16) & 0xff;
    response[2] = (status >> 8) & 0xff;
    response[3] = (status >> 0) & 0xff;
}

static void sd_response_r3_make(SDState *sd, uint8_t *response)
{
    response[0] = (sd->ocr >> 24) & 0xff;
    response[1] = (sd->ocr >> 16) & 0xff;
    response[2] = (sd->ocr >> 8) & 0xff;
    response[3] = (sd->ocr >> 0) & 0xff;
}

static void sd_response_r6_make(SDState *sd, uint8_t *response)
{
    uint16_t arg;
    uint16_t status;

    arg = sd->rca;
    status = ((sd->card_status >> 8) & 0xc000) |
             ((sd->card_status >> 6) & 0x2000) |
              (sd->card_status & 0x1fff);

    response[0] = (arg >> 8) & 0xff;
    response[1] = arg & 0xff;
    response[2] = (status >> 8) & 0xff;
    response[3] = status & 0xff;
}

static void sd_response_r7_make(SDState *sd, uint8_t *response)
{
    response[0] = (sd->vhs >> 24) & 0xff;
    response[1] = (sd->vhs >> 16) & 0xff;
    response[2] = (sd->vhs >>  8) & 0xff;
    response[3] = (sd->vhs >>  0) & 0xff;
}

static void sd_reset(SDState *sd, BlockDriverState *bdrv)
{
    uint64_t size;
    uint64_t sect;

    if (bdrv) {
        bdrv_get_geometry(bdrv, &sect);
    } else {
        sect = 0;
    }
    sect <<= 9;

    size = sect + 1;

    sect = (size >> (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT)) + 1;

    sd->state = sd_idle_state;
    sd->rca = 0x0000;
    sd_set_ocr(sd);
    sd_set_scr(sd);
    sd_set_cid(sd);
    sd_set_csd(sd, size);
    sd_set_cardstatus(sd);
    sd_set_sdstatus(sd);

    sd->bdrv = bdrv;

    if (sd->wp_groups)
        qemu_free(sd->wp_groups);
    sd->wp_switch = bdrv ? bdrv_is_read_only(bdrv) : 0;
    sd->wp_groups = (int *) qemu_mallocz(sizeof(int) * sect);
    memset(sd->function_group, 0, sizeof(int) * 6);
    sd->erase_start = 0;
    sd->erase_end = 0;
    sd->size = size;
    sd->blk_len = 0x200;
    sd->pwd_len = 0;
}

static void sd_cardchange(void *opaque)
{
    SDState *sd = opaque;
    qemu_set_irq(sd->inserted_cb, bdrv_is_inserted(sd->bdrv));
    if (bdrv_is_inserted(sd->bdrv)) {
        sd_reset(sd, sd->bdrv);
        qemu_set_irq(sd->readonly_cb, sd->wp_switch);
    }
}

/* We do not model the chip select pin, so allow the board to select
   whether card should be in SSI or MMC/SD mode.  It is also up to the
   board to ensure that ssi transfers only occur when the chip select
   is asserted.  */
SDState *sd_init(BlockDriverState *bs, int is_spi)
{
    SDState *sd;

    sd = (SDState *) qemu_mallocz(sizeof(SDState));
    sd->buf = qemu_memalign(512, 512);
    sd->spi = is_spi;
    sd->enable = 1;
    sd_reset(sd, bs);
    if (sd->bdrv) {
        bdrv_set_change_cb(sd->bdrv, sd_cardchange, sd);
    }
    return sd;
}

void sd_set_cb(SDState *sd, qemu_irq readonly, qemu_irq insert)
{
    sd->readonly_cb = readonly;
    sd->inserted_cb = insert;
    qemu_set_irq(readonly, bdrv_is_read_only(sd->bdrv));
    qemu_set_irq(insert, bdrv_is_inserted(sd->bdrv));
}

static void sd_erase(SDState *sd)
{
    int i, start, end;
    if (!sd->erase_start || !sd->erase_end) {
        sd->card_status |= ERASE_SEQ_ERROR;
        return;
    }

    start = sd->erase_start >>
            (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT);
    end = sd->erase_end >>
            (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT);
    sd->erase_start = 0;
    sd->erase_end = 0;
    sd->csd[14] |= 0x40;

    for (i = start; i <= end; i ++)
        if (sd->wp_groups[i])
            sd->card_status |= WP_ERASE_SKIP;
}

static uint32_t sd_wpbits(SDState *sd, uint64_t addr)
{
    uint32_t i, wpnum;
    uint32_t ret = 0;

    wpnum = addr >> (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT);

    for (i = 0; i < 32; i ++, wpnum ++, addr += WPGROUP_SIZE)
        if (addr < sd->size && sd->wp_groups[wpnum])
            ret |= (1 << i);

    return ret;
}

static void sd_function_switch(SDState *sd, uint32_t arg)
{
    int i, mode, new_func, crc;
    mode = !!(arg & 0x80000000);

    sd->data[0] = 0x00;		/* Maximum current consumption */
    sd->data[1] = 0x01;
    sd->data[2] = 0x80;		/* Supported group 6 functions */
    sd->data[3] = 0x01;
    sd->data[4] = 0x80;		/* Supported group 5 functions */
    sd->data[5] = 0x01;
    sd->data[6] = 0x80;		/* Supported group 4 functions */
    sd->data[7] = 0x01;
    sd->data[8] = 0x80;		/* Supported group 3 functions */
    sd->data[9] = 0x01;
    sd->data[10] = 0x80;	/* Supported group 2 functions */
    sd->data[11] = 0x43;
    sd->data[12] = 0x80;	/* Supported group 1 functions */
    sd->data[13] = 0x03;
    for (i = 0; i < 6; i ++) {
        new_func = (arg >> (i * 4)) & 0x0f;
        if (mode && new_func != 0x0f)
            sd->function_group[i] = new_func;
        sd->data[14 + (i >> 1)] = new_func << ((i * 4) & 4);
    }
    memset(&sd->data[17], 0, 47);
    crc = sd_crc16(sd->data, 64);
    sd->data[65] = crc >> 8;
    sd->data[66] = crc & 0xff;
}

static inline int sd_wp_addr(SDState *sd, uint32_t addr)
{
    return sd->wp_groups[addr >>
            (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT)];
}

static void sd_lock_command(SDState *sd)
{
    int erase, lock, clr_pwd, set_pwd, pwd_len;
    erase = !!(sd->data[0] & 0x08);
    lock = sd->data[0] & 0x04;
    clr_pwd = sd->data[0] & 0x02;
    set_pwd = sd->data[0] & 0x01;

    if (sd->blk_len > 1)
        pwd_len = sd->data[1];
    else
        pwd_len = 0;

    if (erase) {
        if (!(sd->card_status & CARD_IS_LOCKED) || sd->blk_len > 1 ||
                        set_pwd || clr_pwd || lock || sd->wp_switch ||
                        (sd->csd[14] & 0x20)) {
            sd->card_status |= LOCK_UNLOCK_FAILED;
            return;
        }
        memset(sd->wp_groups, 0, sizeof(int) * (sd->size >>
                        (HWBLOCK_SHIFT + SECTOR_SHIFT + WPGROUP_SHIFT)));
        sd->csd[14] &= ~0x10;
        sd->card_status &= ~CARD_IS_LOCKED;
        sd->pwd_len = 0;
        /* Erasing the entire card here! */
        fprintf(stderr, "SD: Card force-erased by CMD42\n");
        return;
    }

    if (sd->blk_len < 2 + pwd_len ||
                    pwd_len <= sd->pwd_len ||
                    pwd_len > sd->pwd_len + 16) {
        sd->card_status |= LOCK_UNLOCK_FAILED;
        return;
    }

    if (sd->pwd_len && memcmp(sd->pwd, sd->data + 2, sd->pwd_len)) {
        sd->card_status |= LOCK_UNLOCK_FAILED;
        return;
    }

    pwd_len -= sd->pwd_len;
    if ((pwd_len && !set_pwd) ||
                    (clr_pwd && (set_pwd || lock)) ||
                    (lock && !sd->pwd_len && !set_pwd) ||
                    (!set_pwd && !clr_pwd &&
                     (((sd->card_status & CARD_IS_LOCKED) && lock) ||
                      (!(sd->card_status & CARD_IS_LOCKED) && !lock)))) {
        sd->card_status |= LOCK_UNLOCK_FAILED;
        return;
    }

    if (set_pwd) {
        memcpy(sd->pwd, sd->data + 2 + sd->pwd_len, pwd_len);
        sd->pwd_len = pwd_len;
    }

    if (clr_pwd) {
        sd->pwd_len = 0;
    }

    if (lock)
        sd->card_status |= CARD_IS_LOCKED;
    else
        sd->card_status &= ~CARD_IS_LOCKED;
}

static sd_rsp_type_t sd_normal_command(SDState *sd,
                                       SDRequest req)
{
    uint32_t rca = 0x0000;
    uint64_t addr = (sd->ocr & (1 << 30)) ? (uint64_t) req.arg << 9 : req.arg;

    if (sd_cmd_type[req.cmd] == sd_ac || sd_cmd_type[req.cmd] == sd_adtc)
        rca = req.arg >> 16;

    DPRINTF("CMD%d 0x%08x state %d\n", req.cmd, req.arg, sd->state);
    switch (req.cmd) {
    /* Basic commands (Class 0 and Class 1) */
    case 0:	/* CMD0:   GO_IDLE_STATE */
        switch (sd->state) {
        case sd_inactive_state:
            return sd->spi ? sd_r1 : sd_r0;

        default:
            sd->state = sd_idle_state;
            sd_reset(sd, sd->bdrv);
            return sd->spi ? sd_r1 : sd_r0;
        }
        break;

    case 1:	/* CMD1:   SEND_OP_CMD */
        if (!sd->spi)
            goto bad_cmd;

        sd->state = sd_transfer_state;
        return sd_r1;

    case 2:	/* CMD2:   ALL_SEND_CID */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_ready_state:
            sd->state = sd_identification_state;
            return sd_r2_i;

        default:
            break;
        }
        break;

    case 3:	/* CMD3:   SEND_RELATIVE_ADDR */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_identification_state:
        case sd_standby_state:
            sd->state = sd_standby_state;
            sd_set_rca(sd);
            return sd_r6;

        default:
            break;
        }
        break;

    case 4:	/* CMD4:   SEND_DSR */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_standby_state:
            break;

        default:
            break;
        }
        break;

    case 5: /* CMD5: reserved for SDIO cards */
        sd->card_status |= ILLEGAL_COMMAND;
        return sd_r0;

    case 6:	/* CMD6:   SWITCH_FUNCTION */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->mode) {
        case sd_data_transfer_mode:
            sd_function_switch(sd, req.arg);
            sd->state = sd_sendingdata_state;
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 7:	/* CMD7:   SELECT/DESELECT_CARD */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_standby_state:
            if (sd->rca != rca)
                return sd_r0;

            sd->state = sd_transfer_state;
            return sd_r1b;

        case sd_transfer_state:
        case sd_sendingdata_state:
            if (sd->rca == rca)
                break;

            sd->state = sd_standby_state;
            return sd_r1b;

        case sd_disconnect_state:
            if (sd->rca != rca)
                return sd_r0;

            sd->state = sd_programming_state;
            return sd_r1b;

        case sd_programming_state:
            if (sd->rca == rca)
                break;

            sd->state = sd_disconnect_state;
            return sd_r1b;

        default:
            break;
        }
        break;

    case 8:	/* CMD8:   SEND_IF_COND */
        /* Physical Layer Specification Version 2.00 command */
        switch (sd->state) {
        case sd_idle_state:
            sd->vhs = 0;

            /* No response if not exactly one VHS bit is set.  */
            if (!(req.arg >> 8) || (req.arg >> ffs(req.arg & ~0xff)))
                return sd->spi ? sd_r7 : sd_r0;

            /* Accept.  */
            sd->vhs = req.arg;
            return sd_r7;

        default:
            break;
        }
        break;

    case 9:	/* CMD9:   SEND_CSD */
        switch (sd->state) {
        case sd_standby_state:
            if (sd->rca != rca)
                return sd_r0;

            return sd_r2_s;

        case sd_transfer_state:
            if (!sd->spi)
                break;
            sd->state = sd_sendingdata_state;
            memcpy(sd->data, sd->csd, 16);
            sd->data_start = addr;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 10:	/* CMD10:  SEND_CID */
        switch (sd->state) {
        case sd_standby_state:
            if (sd->rca != rca)
                return sd_r0;

            return sd_r2_i;

        case sd_transfer_state:
            if (!sd->spi)
                break;
            sd->state = sd_sendingdata_state;
            memcpy(sd->data, sd->cid, 16);
            sd->data_start = addr;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 11:	/* CMD11:  READ_DAT_UNTIL_STOP */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_sendingdata_state;
            sd->data_start = req.arg;
            sd->data_offset = 0;

            if (sd->data_start + sd->blk_len > sd->size)
                sd->card_status |= ADDRESS_ERROR;
            return sd_r0;

        default:
            break;
        }
        break;

    case 12:	/* CMD12:  STOP_TRANSMISSION */
        switch (sd->state) {
        case sd_sendingdata_state:
            sd->state = sd_transfer_state;
            return sd_r1b;

        case sd_receivingdata_state:
            sd->state = sd_programming_state;
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
            return sd_r1b;

        default:
            break;
        }
        break;

    case 13:	/* CMD13:  SEND_STATUS */
        switch (sd->mode) {
        case sd_data_transfer_mode:
            if (sd->rca != rca)
                return sd_r0;

            return sd_r1;

        default:
            break;
        }
        break;

    case 15:	/* CMD15:  GO_INACTIVE_STATE */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->mode) {
        case sd_data_transfer_mode:
            if (sd->rca != rca)
                return sd_r0;

            sd->state = sd_inactive_state;
            return sd_r0;

        default:
            break;
        }
        break;

    /* Block read commands (Classs 2) */
    case 16:	/* CMD16:  SET_BLOCKLEN */
        switch (sd->state) {
        case sd_transfer_state:
            if (req.arg > (1 << HWBLOCK_SHIFT))
                sd->card_status |= BLOCK_LEN_ERROR;
            else
                sd->blk_len = req.arg;

            return sd_r1;

        default:
            break;
        }
        break;

    case 17:	/* CMD17:  READ_SINGLE_BLOCK */
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_sendingdata_state;
            sd->data_start = addr;
            sd->data_offset = 0;

            if (sd->data_start + sd->blk_len > sd->size)
                sd->card_status |= ADDRESS_ERROR;
            return sd_r1;

        default:
            break;
        }
        break;

    case 18:	/* CMD18:  READ_MULTIPLE_BLOCK */
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_sendingdata_state;
            sd->data_start = addr;
            sd->data_offset = 0;

            if (sd->data_start + sd->blk_len > sd->size)
                sd->card_status |= ADDRESS_ERROR;
            return sd_r1;

        default:
            break;
        }
        break;

    /* Block write commands (Class 4) */
    case 24:	/* CMD24:  WRITE_SINGLE_BLOCK */
        if (sd->spi)
            goto unimplemented_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            /* Writing in SPI mode not implemented.  */
            if (sd->spi)
                break;
            sd->state = sd_receivingdata_state;
            sd->data_start = addr;
            sd->data_offset = 0;
            sd->blk_written = 0;

            if (sd->data_start + sd->blk_len > sd->size)
                sd->card_status |= ADDRESS_ERROR;
            if (sd_wp_addr(sd, sd->data_start))
                sd->card_status |= WP_VIOLATION;
            if (sd->csd[14] & 0x30)
                sd->card_status |= WP_VIOLATION;
            return sd_r1;

        default:
            break;
        }
        break;

    case 25:	/* CMD25:  WRITE_MULTIPLE_BLOCK */
        if (sd->spi)
            goto unimplemented_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            /* Writing in SPI mode not implemented.  */
            if (sd->spi)
                break;
            sd->state = sd_receivingdata_state;
            sd->data_start = addr;
            sd->data_offset = 0;
            sd->blk_written = 0;

            if (sd->data_start + sd->blk_len > sd->size)
                sd->card_status |= ADDRESS_ERROR;
            if (sd_wp_addr(sd, sd->data_start))
                sd->card_status |= WP_VIOLATION;
            if (sd->csd[14] & 0x30)
                sd->card_status |= WP_VIOLATION;
            return sd_r1;

        default:
            break;
        }
        break;

    case 26:	/* CMD26:  PROGRAM_CID */
        if (sd->spi)
            goto bad_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_receivingdata_state;
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 27:	/* CMD27:  PROGRAM_CSD */
        if (sd->spi)
            goto unimplemented_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_receivingdata_state;
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    /* Write protection (Class 6) */
    case 28:	/* CMD28:  SET_WRITE_PROT */
        switch (sd->state) {
        case sd_transfer_state:
            if (addr >= sd->size) {
                sd->card_status = ADDRESS_ERROR;
                return sd_r1b;
            }

            sd->state = sd_programming_state;
            sd->wp_groups[addr >> (HWBLOCK_SHIFT +
                            SECTOR_SHIFT + WPGROUP_SHIFT)] = 1;
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
            return sd_r1b;

        default:
            break;
        }
        break;

    case 29:	/* CMD29:  CLR_WRITE_PROT */
        switch (sd->state) {
        case sd_transfer_state:
            if (addr >= sd->size) {
                sd->card_status = ADDRESS_ERROR;
                return sd_r1b;
            }

            sd->state = sd_programming_state;
            sd->wp_groups[addr >> (HWBLOCK_SHIFT +
                            SECTOR_SHIFT + WPGROUP_SHIFT)] = 0;
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
            return sd_r1b;

        default:
            break;
        }
        break;

    case 30:	/* CMD30:  SEND_WRITE_PROT */
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_sendingdata_state;
            *(uint32_t *) sd->data = sd_wpbits(sd, req.arg);
            sd->data_start = addr;
            sd->data_offset = 0;
            return sd_r1b;

        default:
            break;
        }
        break;

    /* Erase commands (Class 5) */
    case 32:	/* CMD32:  ERASE_WR_BLK_START */
        switch (sd->state) {
        case sd_transfer_state:
            sd->erase_start = req.arg;
            return sd_r1;

        default:
            break;
        }
        break;

    case 33:	/* CMD33:  ERASE_WR_BLK_END */
        switch (sd->state) {
        case sd_transfer_state:
            sd->erase_end = req.arg;
            return sd_r1;

        default:
            break;
        }
        break;

    case 38:	/* CMD38:  ERASE */
        switch (sd->state) {
        case sd_transfer_state:
            if (sd->csd[14] & 0x30) {
                sd->card_status |= WP_VIOLATION;
                return sd_r1b;
            }

            sd->state = sd_programming_state;
            sd_erase(sd);
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
            return sd_r1b;

        default:
            break;
        }
        break;

    /* Lock card commands (Class 7) */
    case 42:	/* CMD42:  LOCK_UNLOCK */
        if (sd->spi)
            goto unimplemented_cmd;
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_receivingdata_state;
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    /* Application specific commands (Class 8) */
    case 55:	/* CMD55:  APP_CMD */
        if (sd->rca != rca)
            return sd_r0;

        sd->card_status |= APP_CMD;
        return sd_r1;

    case 56:	/* CMD56:  GEN_CMD */
        fprintf(stderr, "SD: GEN_CMD 0x%08x\n", req.arg);

        switch (sd->state) {
        case sd_transfer_state:
            sd->data_offset = 0;
            if (req.arg & 1)
                sd->state = sd_sendingdata_state;
            else
                sd->state = sd_receivingdata_state;
            return sd_r1;

        default:
            break;
        }
        break;

    default:
    bad_cmd:
        sd->card_status |= ILLEGAL_COMMAND;

        fprintf(stderr, "SD: Unknown CMD%i\n", req.cmd);
        return sd_r0;

    unimplemented_cmd:
        /* Commands that are recognised but not yet implemented in SPI mode.  */
        sd->card_status |= ILLEGAL_COMMAND;
        fprintf(stderr, "SD: CMD%i not implemented in SPI mode\n", req.cmd);
        return sd_r0;
    }

    sd->card_status |= ILLEGAL_COMMAND;
    fprintf(stderr, "SD: CMD%i in a wrong state\n", req.cmd);
    return sd_r0;
}

static sd_rsp_type_t sd_app_command(SDState *sd,
                                    SDRequest req)
{
    DPRINTF("ACMD%d 0x%08x\n", req.cmd, req.arg);
    switch (req.cmd) {
    case 6:	/* ACMD6:  SET_BUS_WIDTH */
        switch (sd->state) {
        case sd_transfer_state:
            sd->sd_status[0] &= 0x3f;
            sd->sd_status[0] |= (req.arg & 0x03) << 6;
            return sd_r1;

        default:
            break;
        }
        break;

    case 13:	/* ACMD13: SD_STATUS */
        switch (sd->state) {
        case sd_transfer_state:
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 22:	/* ACMD22: SEND_NUM_WR_BLOCKS */
        switch (sd->state) {
        case sd_transfer_state:
            *(uint32_t *) sd->data = sd->blk_written;

            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    case 23:	/* ACMD23: SET_WR_BLK_ERASE_COUNT */
        switch (sd->state) {
        case sd_transfer_state:
            return sd_r1;

        default:
            break;
        }
        break;

    case 41:	/* ACMD41: SD_APP_OP_COND */
        if (sd->spi) {
            /* SEND_OP_CMD */
            sd->state = sd_transfer_state;
            return sd_r1;
        }
        switch (sd->state) {
        case sd_idle_state:
            /* We accept any voltage.  10000 V is nothing.  */
            if (req.arg)
                sd->state = sd_ready_state;

            return sd_r3;

        default:
            break;
        }
        break;

    case 42:	/* ACMD42: SET_CLR_CARD_DETECT */
        switch (sd->state) {
        case sd_transfer_state:
            /* Bringing in the 50KOhm pull-up resistor... Done.  */
            return sd_r1;

        default:
            break;
        }
        break;

    case 51:	/* ACMD51: SEND_SCR */
        switch (sd->state) {
        case sd_transfer_state:
            sd->state = sd_sendingdata_state;
            sd->data_start = 0;
            sd->data_offset = 0;
            return sd_r1;

        default:
            break;
        }
        break;

    default:
        /* Fall back to standard commands.  */
        sd->card_status &= ~APP_CMD;
        return sd_normal_command(sd, req);
    }

    fprintf(stderr, "SD: ACMD%i in a wrong state\n", req.cmd);
    return sd_r0;
}

int sd_do_command(SDState *sd, SDRequest *req,
                  uint8_t *response) {
    uint32_t last_status = sd->card_status;
    sd_rsp_type_t rtype;
    int rsplen;

    if (!sd->bdrv || !bdrv_is_inserted(sd->bdrv) || !sd->enable) {
        return 0;
    }

    if (sd_req_crc_validate(req)) {
        sd->card_status &= ~COM_CRC_ERROR;
        return 0;
    }

    sd->card_status &= ~CARD_STATUS_B;
    sd_set_status(sd);

    if (last_status & CARD_IS_LOCKED)
        if (((last_status & APP_CMD) &&
                                 req->cmd == 41) ||
                        (!(last_status & APP_CMD) &&
                         (sd_cmd_class[req->cmd] == 0 ||
                          sd_cmd_class[req->cmd] == 7 ||
                          req->cmd == 16 || req->cmd == 55))) {
            sd->card_status |= ILLEGAL_COMMAND;
            fprintf(stderr, "SD: Card is locked\n");
            return 0;
        }

    if (last_status & APP_CMD) {
        rtype = sd_app_command(sd, *req);
        sd->card_status &= ~APP_CMD;
    } else
        rtype = sd_normal_command(sd, *req);

    sd->current_cmd = req->cmd;

    switch (rtype) {
    case sd_r1:
    case sd_r1b:
        sd_response_r1_make(sd, response, last_status);
        rsplen = 4;
        break;

    case sd_r2_i:
        memcpy(response, sd->cid, sizeof(sd->cid));
        rsplen = 16;
        break;

    case sd_r2_s:
        memcpy(response, sd->csd, sizeof(sd->csd));
        rsplen = 16;
        break;

    case sd_r3:
        sd_response_r3_make(sd, response);
        rsplen = 4;
        break;

    case sd_r6:
        sd_response_r6_make(sd, response);
        rsplen = 4;
        break;

    case sd_r7:
        sd_response_r7_make(sd, response);
        rsplen = 4;
        break;

    case sd_r0:
    default:
        rsplen = 0;
        break;
    }

    if (sd->card_status & ILLEGAL_COMMAND)
        rsplen = 0;

#ifdef DEBUG_SD
    if (rsplen) {
        int i;
        DPRINTF("Response:");
        for (i = 0; i < rsplen; i++)
            printf(" %02x", response[i]);
        printf(" state %d\n", sd->state);
    } else {
        DPRINTF("No response %d\n", sd->state);
    }
#endif

    return rsplen;
}

static void sd_blk_read(SDState *sd, uint64_t addr, uint32_t len)
{
    uint64_t end = addr + len;

    DPRINTF("sd_blk_read: addr = 0x%08llx, len = %d\n",
            (unsigned long long) addr, len);
    if (!sd->bdrv || bdrv_read(sd->bdrv, addr >> 9, sd->buf, 1) == -1) {
        fprintf(stderr, "sd_blk_read: read error on host side\n");
        return;
    }

    if (end > (addr & ~511) + 512) {
        memcpy(sd->data, sd->buf + (addr & 511), 512 - (addr & 511));

        if (bdrv_read(sd->bdrv, end >> 9, sd->buf, 1) == -1) {
            fprintf(stderr, "sd_blk_read: read error on host side\n");
            return;
        }
        memcpy(sd->data + 512 - (addr & 511), sd->buf, end & 511);
    } else
        memcpy(sd->data, sd->buf + (addr & 511), len);
}

static void sd_blk_write(SDState *sd, uint64_t addr, uint32_t len)
{
    uint64_t end = addr + len;

    if ((addr & 511) || len < 512)
        if (!sd->bdrv || bdrv_read(sd->bdrv, addr >> 9, sd->buf, 1) == -1) {
            fprintf(stderr, "sd_blk_write: read error on host side\n");
            return;
        }

    if (end > (addr & ~511) + 512) {
        memcpy(sd->buf + (addr & 511), sd->data, 512 - (addr & 511));
        if (bdrv_write(sd->bdrv, addr >> 9, sd->buf, 1) == -1) {
            fprintf(stderr, "sd_blk_write: write error on host side\n");
            return;
        }

        if (bdrv_read(sd->bdrv, end >> 9, sd->buf, 1) == -1) {
            fprintf(stderr, "sd_blk_write: read error on host side\n");
            return;
        }
        memcpy(sd->buf, sd->data + 512 - (addr & 511), end & 511);
        if (bdrv_write(sd->bdrv, end >> 9, sd->buf, 1) == -1)
            fprintf(stderr, "sd_blk_write: write error on host side\n");
    } else {
        memcpy(sd->buf + (addr & 511), sd->data, len);
        if (!sd->bdrv || bdrv_write(sd->bdrv, addr >> 9, sd->buf, 1) == -1)
            fprintf(stderr, "sd_blk_write: write error on host side\n");
    }
}

#define BLK_READ_BLOCK(a, len)	sd_blk_read(sd, a, len)
#define BLK_WRITE_BLOCK(a, len)	sd_blk_write(sd, a, len)
#define APP_READ_BLOCK(a, len)	memset(sd->data, 0xec, len)
#define APP_WRITE_BLOCK(a, len)

void sd_write_data(SDState *sd, uint8_t value)
{
    int i;

    if (!sd->bdrv || !bdrv_is_inserted(sd->bdrv) || !sd->enable)
        return;

    if (sd->state != sd_receivingdata_state) {
        fprintf(stderr, "sd_write_data: not in Receiving-Data state\n");
        return;
    }

    if (sd->card_status & (ADDRESS_ERROR | WP_VIOLATION))
        return;

    switch (sd->current_cmd) {
    case 24:	/* CMD24:  WRITE_SINGLE_BLOCK */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sd->blk_len) {
            /* TODO: Check CRC before committing */
            sd->state = sd_programming_state;
            BLK_WRITE_BLOCK(sd->data_start, sd->data_offset);
            sd->blk_written ++;
            sd->csd[14] |= 0x40;
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
        }
        break;

    case 25:	/* CMD25:  WRITE_MULTIPLE_BLOCK */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sd->blk_len) {
            /* TODO: Check CRC before committing */
            sd->state = sd_programming_state;
            BLK_WRITE_BLOCK(sd->data_start, sd->data_offset);
            sd->blk_written ++;
            sd->data_start += sd->blk_len;
            sd->data_offset = 0;
            if (sd->data_start + sd->blk_len > sd->size) {
                sd->card_status |= ADDRESS_ERROR;
                break;
            }
            if (sd_wp_addr(sd, sd->data_start)) {
                sd->card_status |= WP_VIOLATION;
                break;
            }
            sd->csd[14] |= 0x40;

            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_receivingdata_state;
        }
        break;

    case 26:	/* CMD26:  PROGRAM_CID */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sizeof(sd->cid)) {
            /* TODO: Check CRC before committing */
            sd->state = sd_programming_state;
            for (i = 0; i < sizeof(sd->cid); i ++)
                if ((sd->cid[i] | 0x00) != sd->data[i])
                    sd->card_status |= CID_CSD_OVERWRITE;

            if (!(sd->card_status & CID_CSD_OVERWRITE))
                for (i = 0; i < sizeof(sd->cid); i ++) {
                    sd->cid[i] |= 0x00;
                    sd->cid[i] &= sd->data[i];
                }
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
        }
        break;

    case 27:	/* CMD27:  PROGRAM_CSD */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sizeof(sd->csd)) {
            /* TODO: Check CRC before committing */
            sd->state = sd_programming_state;
            for (i = 0; i < sizeof(sd->csd); i ++)
                if ((sd->csd[i] | sd_csd_rw_mask[i]) !=
                    (sd->data[i] | sd_csd_rw_mask[i]))
                    sd->card_status |= CID_CSD_OVERWRITE;

            /* Copy flag (OTP) & Permanent write protect */
            if (sd->csd[14] & ~sd->data[14] & 0x60)
                sd->card_status |= CID_CSD_OVERWRITE;

            if (!(sd->card_status & CID_CSD_OVERWRITE))
                for (i = 0; i < sizeof(sd->csd); i ++) {
                    sd->csd[i] |= sd_csd_rw_mask[i];
                    sd->csd[i] &= sd->data[i];
                }
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
        }
        break;

    case 42:	/* CMD42:  LOCK_UNLOCK */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sd->blk_len) {
            /* TODO: Check CRC before committing */
            sd->state = sd_programming_state;
            sd_lock_command(sd);
            /* Bzzzzzzztt .... Operation complete.  */
            sd->state = sd_transfer_state;
        }
        break;

    case 56:	/* CMD56:  GEN_CMD */
        sd->data[sd->data_offset ++] = value;
        if (sd->data_offset >= sd->blk_len) {
            APP_WRITE_BLOCK(sd->data_start, sd->data_offset);
            sd->state = sd_transfer_state;
        }
        break;

    default:
        fprintf(stderr, "sd_write_data: unknown command\n");
        break;
    }
}

uint8_t sd_read_data(SDState *sd)
{
    /* TODO: Append CRCs */
    uint8_t ret;
    int io_len;

    if (!sd->bdrv || !bdrv_is_inserted(sd->bdrv) || !sd->enable)
        return 0x00;

    if (sd->state != sd_sendingdata_state) {
        fprintf(stderr, "sd_read_data: not in Sending-Data state\n");
        return 0x00;
    }

    if (sd->card_status & (ADDRESS_ERROR | WP_VIOLATION))
        return 0x00;

    io_len = (sd->ocr & (1 << 30)) ? 512 : sd->blk_len;

    switch (sd->current_cmd) {
    case 6:	/* CMD6:   SWITCH_FUNCTION */
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= 64)
            sd->state = sd_transfer_state;
        break;

    case 9:	/* CMD9:   SEND_CSD */
    case 10:	/* CMD10:  SEND_CID */
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= 16)
            sd->state = sd_transfer_state;
        break;

    case 11:	/* CMD11:  READ_DAT_UNTIL_STOP */
        if (sd->data_offset == 0)
            BLK_READ_BLOCK(sd->data_start, io_len);
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= io_len) {
            sd->data_start += io_len;
            sd->data_offset = 0;
            if (sd->data_start + io_len > sd->size) {
                sd->card_status |= ADDRESS_ERROR;
                break;
            }
        }
        break;

    case 13:	/* ACMD13: SD_STATUS */
        ret = sd->sd_status[sd->data_offset ++];

        if (sd->data_offset >= sizeof(sd->sd_status))
            sd->state = sd_transfer_state;
        break;

    case 17:	/* CMD17:  READ_SINGLE_BLOCK */
        if (sd->data_offset == 0)
            BLK_READ_BLOCK(sd->data_start, io_len);
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= io_len)
            sd->state = sd_transfer_state;
        break;

    case 18:	/* CMD18:  READ_MULTIPLE_BLOCK */
        if (sd->data_offset == 0)
            BLK_READ_BLOCK(sd->data_start, io_len);
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= io_len) {
            sd->data_start += io_len;
            sd->data_offset = 0;
            if (sd->data_start + io_len > sd->size) {
                sd->card_status |= ADDRESS_ERROR;
                break;
            }
        }
        break;

    case 22:	/* ACMD22: SEND_NUM_WR_BLOCKS */
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= 4)
            sd->state = sd_transfer_state;
        break;

    case 30:	/* CMD30:  SEND_WRITE_PROT */
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= 4)
            sd->state = sd_transfer_state;
        break;

    case 51:	/* ACMD51: SEND_SCR */
        ret = sd->scr[sd->data_offset ++];

        if (sd->data_offset >= sizeof(sd->scr))
            sd->state = sd_transfer_state;
        break;

    case 56:	/* CMD56:  GEN_CMD */
        if (sd->data_offset == 0)
            APP_READ_BLOCK(sd->data_start, sd->blk_len);
        ret = sd->data[sd->data_offset ++];

        if (sd->data_offset >= sd->blk_len)
            sd->state = sd_transfer_state;
        break;

    default:
        fprintf(stderr, "sd_read_data: unknown command\n");
        return 0x00;
    }

    return ret;
}

int sd_data_ready(SDState *sd)
{
    return sd->state == sd_sendingdata_state;
}

void sd_enable(SDState *sd, int enable)
{
    sd->enable = enable;
}