source: mainline/uspace/srv/bd/ata_bd/ata_bd.c@ aa893e0

/*
 * Copyright (c) 2009 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 */

/** @addtogroup bd
 * @{
 */

/**
 * @file
 * @brief ATA disk driver
 *
 * This driver supports CHS, 28-bit and 48-bit LBA addressing. It only uses
 * PIO transfers. There is no support DMA, the PACKET feature set or any other
 * fancy features such as S.M.A.R.T, removable devices, etc.
 *
 * This driver is based on the ATA-1, ATA-2, ATA-3 and ATA/ATAPI-4 through 7
 * standards, as published by the ANSI, NCITS and INCITS standards bodies,
 * which are freely available. This driver contains no vendor-specific
 * code at this moment.
 *
 * The driver services a single controller which can have up to two disks
 * attached.
 */

#include <stdio.h>
#include <libarch/ddi.h>
#include <ddi.h>
#include <ipc/ipc.h>
#include <ipc/bd.h>
#include <async.h>
#include <as.h>
#include <fibril_synch.h>
#include <stdint.h>
#include <str.h>
#include <devmap.h>
#include <sys/types.h>
#include <inttypes.h>
#include <errno.h>
#include <bool.h>
#include <byteorder.h>
#include <task.h>
#include <macros.h>

#include "ata_hw.h"
#include "ata_bd.h"

#define NAME       "ata_bd"
#define NAMESPACE  "bd"

/** Number of defined legacy controller base addresses. */
#define LEGACY_CTLS 4

/**
 * Size of data returned from Identify Device or Identify Packet Device
 * command.
 */
static const size_t identify_data_size = 512;

/** Size of the communication area. */
static size_t comm_size;

/** I/O base address of the command registers. */
static uintptr_t cmd_physical;
/** I/O base address of the control registers. */
static uintptr_t ctl_physical;

/** I/O base addresses for legacy (ISA-compatible) controllers. */
static ata_base_t legacy_base[LEGACY_CTLS] = {
        { 0x1f0, 0x3f0 },
        { 0x170, 0x370 },
        { 0x1e8, 0x3e8 },
        { 0x168, 0x368 }
};

static ata_cmd_t *cmd;
static ata_ctl_t *ctl;

/** Per-disk state. */
static disk_t disk[MAX_DISKS];

static void print_syntax(void);
static int ata_bd_init(void);
static void ata_bd_connection(ipc_callid_t iid, ipc_call_t *icall);
static int ata_bd_read_blocks(int disk_id, uint64_t ba, size_t cnt,
    void *buf);
static int ata_bd_write_blocks(int disk_id, uint64_t ba, size_t cnt,
    const void *buf);
static int ata_rcmd_read(int disk_id, uint64_t ba, size_t cnt,
    void *buf);
static int ata_rcmd_write(int disk_id, uint64_t ba, size_t cnt,
    const void *buf);
static int disk_init(disk_t *d, int disk_id);
static int drive_identify(int drive_id, void *buf);
static int identify_pkt_dev(int dev_idx, void *buf);
static int ata_cmd_packet(int dev_idx, const void *cpkt, size_t cpkt_size,
    void *obuf, size_t obuf_size);
static int ata_pcmd_inquiry(int dev_idx, void *obuf, size_t obuf_size);
static int ata_pcmd_read_12(int dev_idx, uint64_t ba, size_t cnt,
    void *obuf, size_t obuf_size);
static void disk_print_summary(disk_t *d);
static int coord_calc(disk_t *d, uint64_t ba, block_coord_t *bc);
static void coord_sc_program(const block_coord_t *bc, uint16_t scnt);
static int wait_status(unsigned set, unsigned n_reset, uint8_t *pstatus,
    unsigned timeout);

int main(int argc, char **argv)
{
        char name[16];
        int i, rc;
        int n_disks;
        unsigned ctl_num;
        char *eptr;

        printf(NAME ": ATA disk driver\n");

        if (argc > 1) {
                ctl_num = strtoul(argv[1], &eptr, 0);
                if (*eptr != '\0' || ctl_num == 0 || ctl_num > 4) {
                        printf("Invalid argument.\n");
                        print_syntax();
                        return -1;
                }
        } else {
                ctl_num = 1;
        }

        cmd_physical = legacy_base[ctl_num - 1].cmd;
        ctl_physical = legacy_base[ctl_num - 1].ctl;

        printf("I/O address %p/%p\n", (void *) cmd_physical,
            (void *) ctl_physical);

        if (ata_bd_init() != EOK)
                return -1;

        for (i = 0; i < MAX_DISKS; i++) {
                printf("Identify drive %d... ", i);
                fflush(stdout);

                rc = disk_init(&disk[i], i);

                if (rc == EOK) {
                        disk_print_summary(&disk[i]);
                } else {
                        printf("Not found.\n");
                }
        }

        n_disks = 0;

        for (i = 0; i < MAX_DISKS; i++) {
                /* Skip unattached drives. */
                if (disk[i].present == false)
                        continue;
                
                snprintf(name, 16, "%s/ata%udisk%d", NAMESPACE, ctl_num, i);
                rc = devmap_device_register(name, &disk[i].devmap_handle);
                if (rc != EOK) {
                        printf(NAME ": Unable to register device %s.\n", name);
                        return rc;
                }
                ++n_disks;
        }

        if (n_disks == 0) {
                printf("No disks detected.\n");
                return -1;
        }

        printf(NAME ": Accepting connections\n");
        task_retval(0);
        async_manager();

        /* Not reached */
        return 0;
}


static void print_syntax(void)
{
        printf("Syntax: " NAME " <controller_number>\n");
        printf("Controller number = 1..4\n");
}

/** Print one-line device summary. */
static void disk_print_summary(disk_t *d)
{
        uint64_t mbytes;

        printf("%s: ", d->model);

        if (d->dev_type == ata_reg_dev) {
                switch (d->amode) {
                case am_chs:
                        printf("CHS %u cylinders, %u heads, %u sectors",
                            disk->geom.cylinders, disk->geom.heads,
                            disk->geom.sectors);
                        break;
                case am_lba28:
                        printf("LBA-28");
                        break;
                case am_lba48:
                        printf("LBA-48");
                        break;
                }
        } else {
                printf("PACKET");
        }

        printf(" %" PRIu64 " blocks", d->blocks);

        mbytes = d->blocks / (2 * 1024);
        if (mbytes > 0)
                printf(" %" PRIu64 " MB.", mbytes);

        printf("\n");
}

/** Register driver and enable device I/O. */
static int ata_bd_init(void)
{
        void *vaddr;
        int rc;

        rc = devmap_driver_register(NAME, ata_bd_connection);
        if (rc < 0) {
                printf(NAME ": Unable to register driver.\n");
                return rc;
        }

        rc = pio_enable((void *) cmd_physical, sizeof(ata_cmd_t), &vaddr);
        if (rc != EOK) {
                printf(NAME ": Could not initialize device I/O space.\n");
                return rc;
        }

        cmd = vaddr;

        rc = pio_enable((void *) ctl_physical, sizeof(ata_ctl_t), &vaddr);
        if (rc != EOK) {
                printf(NAME ": Could not initialize device I/O space.\n");
                return rc;
        }

        ctl = vaddr;


        return EOK;
}

/** Block device connection handler */
static void ata_bd_connection(ipc_callid_t iid, ipc_call_t *icall)
{
        void *fs_va = NULL;
        ipc_callid_t callid;
        ipc_call_t call;
        sysarg_t method;
        devmap_handle_t dh;
        int flags;
        int retval;
        uint64_t ba;
        size_t cnt;
        int disk_id, i;

        /* Get the device handle. */
        dh = IPC_GET_ARG1(*icall);

        /* Determine which disk device is the client connecting to. */
        disk_id = -1;
        for (i = 0; i < MAX_DISKS; i++)
                if (disk[i].devmap_handle == dh)
                        disk_id = i;

        if (disk_id < 0 || disk[disk_id].present == false) {
                ipc_answer_0(iid, EINVAL);
                return;
        }

        /* Answer the IPC_M_CONNECT_ME_TO call. */
        ipc_answer_0(iid, EOK);

        if (!async_share_out_receive(&callid, &comm_size, &flags)) {
                ipc_answer_0(callid, EHANGUP);
                return;
        }

        fs_va = as_get_mappable_page(comm_size);
        if (fs_va == NULL) {
                ipc_answer_0(callid, EHANGUP);
                return;
        }

        (void) async_share_out_finalize(callid, fs_va);

        while (1) {
                callid = async_get_call(&call);
                method = IPC_GET_IMETHOD(call);
                switch (method) {
                case IPC_M_PHONE_HUNGUP:
                        /* The other side has hung up. */
                        ipc_answer_0(callid, EOK);
                        return;
                case BD_READ_BLOCKS:
                        ba = MERGE_LOUP32(IPC_GET_ARG1(call),
                            IPC_GET_ARG2(call));
                        cnt = IPC_GET_ARG3(call);
                        if (cnt * disk[disk_id].block_size > comm_size) {
                                retval = ELIMIT;
                                break;
                        }
                        retval = ata_bd_read_blocks(disk_id, ba, cnt, fs_va);
                        break;
                case BD_WRITE_BLOCKS:
                        ba = MERGE_LOUP32(IPC_GET_ARG1(call),
                            IPC_GET_ARG2(call));
                        cnt = IPC_GET_ARG3(call);
                        if (cnt * disk[disk_id].block_size > comm_size) {
                                retval = ELIMIT;
                                break;
                        }
                        retval = ata_bd_write_blocks(disk_id, ba, cnt, fs_va);
                        break;
                case BD_GET_BLOCK_SIZE:
                        ipc_answer_1(callid, EOK, disk[disk_id].block_size);
                        continue;
                case BD_GET_NUM_BLOCKS:
                        ipc_answer_2(callid, EOK, LOWER32(disk[disk_id].blocks),
                            UPPER32(disk[disk_id].blocks));
                        continue;
                default:
                        retval = EINVAL;
                        break;
                }
                ipc_answer_0(callid, retval);
        }
}

/** Initialize a disk.
 *
 * Probes for a disk, determines its parameters and initializes
 * the disk structure.
 */
static int disk_init(disk_t *d, int disk_id)
{
        identify_data_t idata;
        uint8_t model[40];
        ata_inquiry_data_t inq_data;
        uint16_t w;
        uint8_t c;
        size_t pos, len;
        int rc;
        unsigned i;

        d->present = false;
        fibril_mutex_initialize(&d->lock);

        /* Try identify command. */
        rc = drive_identify(disk_id, &idata);
        if (rc == EOK) {
                /* Success. It's a register (non-packet) device. */
                printf("ATA register-only device found.\n");
                d->dev_type = ata_reg_dev;
        } else if (rc == EIO) {
                /*
                 * There is something, but not a register device.
                 * It could be a packet device.
                 */
                rc = identify_pkt_dev(disk_id, &idata);
                if (rc == EOK) {
                        /* We have a packet device. */
                        d->dev_type = ata_pkt_dev;
                } else {
                        /* Nope. Something's there, but not recognized. */
                        return EIO;
                }
        } else {
                /* Operation timed out. That means there is no device there. */
                return EIO;
        }

        printf("device caps: 0x%04x\n", idata.caps);
        if (d->dev_type == ata_pkt_dev) {
                /* Packet device */
                d->amode = 0;

                d->geom.cylinders = 0;
                d->geom.heads = 0;
                d->geom.sectors = 0;

                d->blocks = 0;
        } else if ((idata.caps & rd_cap_lba) == 0) {
                /* Device only supports CHS addressing. */
                d->amode = am_chs;

                d->geom.cylinders = idata.cylinders;
                d->geom.heads = idata.heads;
                d->geom.sectors = idata.sectors;

                d->blocks = d->geom.cylinders * d->geom.heads * d->geom.sectors;
        } else if ((idata.cmd_set1 & cs1_addr48) == 0) {
                /* Device only supports LBA-28 addressing. */
                d->amode = am_lba28;

                d->geom.cylinders = 0;
                d->geom.heads = 0;
                d->geom.sectors = 0;

                d->blocks =
                     (uint32_t) idata.total_lba28_0 | 
                    ((uint32_t) idata.total_lba28_1 << 16);
        } else {
                /* Device supports LBA-48 addressing. */
                d->amode = am_lba48;

                d->geom.cylinders = 0;
                d->geom.heads = 0;
                d->geom.sectors = 0;

                d->blocks =
                     (uint64_t) idata.total_lba48_0 |
                    ((uint64_t) idata.total_lba48_1 << 16) |
                    ((uint64_t) idata.total_lba48_2 << 32) | 
                    ((uint64_t) idata.total_lba48_3 << 48);
        }

        /*
         * Convert model name to string representation.
         */
        for (i = 0; i < 20; i++) {
                w = idata.model_name[i];
                model[2 * i] = w >> 8;
                model[2 * i + 1] = w & 0x00ff;
        }

        len = 40;
        while (len > 0 && model[len - 1] == 0x20)
                --len;

        pos = 0;
        for (i = 0; i < len; ++i) {
                c = model[i];
                if (c >= 0x80) c = '?';

                chr_encode(c, d->model, &pos, 40);
        }
        d->model[pos] = '\0';

        if (d->dev_type == ata_pkt_dev) {
                /* Send inquiry. */
                rc = ata_pcmd_inquiry(0, &inq_data, sizeof(inq_data));
                if (rc != EOK) {
                        printf("Device inquiry failed.\n");
                        d->present = false;
                        return EIO;
                }

                /* Check device type. */
                if (INQUIRY_PDEV_TYPE(inq_data.pdev_type) != PDEV_TYPE_CDROM)
                        printf("Warning: Peripheral device type is not CD-ROM.\n");

                /* Assume 2k block size for now. */
                d->block_size = 2048;
        } else {
                /* Assume register Read always uses 512-byte blocks. */
                d->block_size = 512;
        }

        d->present = true;
        return EOK;
}

/** Read multiple blocks from the device. */
static int ata_bd_read_blocks(int disk_id, uint64_t ba, size_t cnt,
    void *buf) {

        int rc;

        while (cnt > 0) {
                if (disk[disk_id].dev_type == ata_reg_dev)
                        rc = ata_rcmd_read(disk_id, ba, 1, buf);
                else
                        rc = ata_pcmd_read_12(disk_id, ba, 1, buf,
                            disk[disk_id].block_size);

                if (rc != EOK)
                        return rc;

                ++ba;
                --cnt;
                buf += disk[disk_id].block_size;
        }

        return EOK;
}

/** Write multiple blocks to the device. */
static int ata_bd_write_blocks(int disk_id, uint64_t ba, size_t cnt,
    const void *buf) {

        int rc;

        if (disk[disk_id].dev_type != ata_reg_dev)
                return ENOTSUP;

        while (cnt > 0) {
                rc = ata_rcmd_write(disk_id, ba, 1, buf);
                if (rc != EOK)
                        return rc;

                ++ba;
                --cnt;
                buf += disk[disk_id].block_size;
        }

        return EOK;
}

/** Issue IDENTIFY command.
 *
 * Reads @c identify data into the provided buffer. This is used to detect
 * whether an ATA device is present and if so, to determine its parameters.
 *
 * @param disk_id       Device ID, 0 or 1.
 * @param buf           Pointer to a 512-byte buffer.
 *
 * @return              ETIMEOUT on timeout (this can mean the device is
 *                      not present). EIO if device responds with error.
 */
static int drive_identify(int disk_id, void *buf)
{
        uint16_t data;
        uint8_t status;
        uint8_t drv_head;
        size_t i;

        drv_head = ((disk_id != 0) ? DHR_DRV : 0);

        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_PROBE) != EOK)
                return ETIMEOUT;

        pio_write_8(&cmd->drive_head, drv_head);

        /*
         * This is where we would most likely expect a non-existing device to
         * show up by not setting SR_DRDY.
         */
        if (wait_status(SR_DRDY, ~SR_BSY, NULL, TIMEOUT_PROBE) != EOK)
                return ETIMEOUT;

        pio_write_8(&cmd->command, CMD_IDENTIFY_DRIVE);

        if (wait_status(0, ~SR_BSY, &status, TIMEOUT_PROBE) != EOK)
                return ETIMEOUT;

        /* Read data from the disk buffer. */

        if ((status & SR_DRQ) != 0) {
                for (i = 0; i < identify_data_size / 2; i++) {
                        data = pio_read_16(&cmd->data_port);
                        ((uint16_t *) buf)[i] = data;
                }
        }

        if ((status & SR_ERR) != 0) {
                return EIO;
        }

        return EOK;
}

/** Issue Identify Packet Device command.
 *
 * Reads @c identify data into the provided buffer. This is used to detect
 * whether an ATAPI device is present and if so, to determine its parameters.
 *
 * @param dev_idx       Device index, 0 or 1.
 * @param buf           Pointer to a 512-byte buffer.
 */
static int identify_pkt_dev(int dev_idx, void *buf)
{
        uint16_t data;
        uint8_t status;
        uint8_t drv_head;
        size_t i;

        drv_head = ((dev_idx != 0) ? DHR_DRV : 0);

        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_PROBE) != EOK)
                return EIO;

        pio_write_8(&cmd->drive_head, drv_head);

        /* For ATAPI commands we do not need to wait for DRDY. */
        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_PROBE) != EOK)
                return EIO;

        pio_write_8(&cmd->command, CMD_IDENTIFY_PKT_DEV);

        if (wait_status(0, ~SR_BSY, &status, TIMEOUT_BSY) != EOK)
                return EIO;

        /* Read data from the device buffer. */

        if ((status & SR_DRQ) != 0) {
                for (i = 0; i < identify_data_size / 2; i++) {
                        data = pio_read_16(&cmd->data_port);
                        ((uint16_t *) buf)[i] = data;
                }
        }

        if ((status & SR_ERR) != 0)
                return EIO;

        return EOK;
}

/** Issue packet command (i. e. write a command packet to the device).
 *
 * Only data-in commands are supported (e.g. inquiry, read).
 *
 * @param dev_idx       Device index (0 or 1)
 * @param obuf          Buffer for storing data read from device
 * @param obuf_size     Size of obuf in bytes
 *
 * @return EOK on success, EIO on error.
 */
static int ata_cmd_packet(int dev_idx, const void *cpkt, size_t cpkt_size,
    void *obuf, size_t obuf_size)
{
        size_t i;
        uint8_t status;
        uint8_t drv_head;
        disk_t *d;
        size_t data_size;
        uint16_t val;

        d = &disk[dev_idx];
        fibril_mutex_lock(&d->lock);

        /* New value for Drive/Head register */
        drv_head =
            ((dev_idx != 0) ? DHR_DRV : 0);

        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_PROBE) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        pio_write_8(&cmd->drive_head, drv_head);

        if (wait_status(0, ~(SR_BSY|SR_DRQ), NULL, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Byte count <- max. number of bytes we can read in one transfer. */
        pio_write_8(&cmd->cylinder_low, 0xfe);
        pio_write_8(&cmd->cylinder_high, 0xff);

        pio_write_8(&cmd->command, CMD_PACKET);

        if (wait_status(SR_DRQ, ~SR_BSY, &status, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Write command packet. */
        for (i = 0; i < (cpkt_size + 1) / 2; i++)
                pio_write_16(&cmd->data_port, ((uint16_t *) cpkt)[i]);

        if (wait_status(0, ~SR_BSY, &status, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        if ((status & SR_DRQ) == 0) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Read byte count. */
        data_size = (uint16_t) pio_read_8(&cmd->cylinder_low) +
            ((uint16_t) pio_read_8(&cmd->cylinder_high) << 8);

        /* Check whether data fits into output buffer. */
        if (data_size > obuf_size) {
                /* Output buffer is too small to store data. */
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Read data from the device buffer. */
        for (i = 0; i < (data_size + 1) / 2; i++) {
                val = pio_read_16(&cmd->data_port);
                ((uint16_t *) obuf)[i] = val;
        }

        if (status & SR_ERR) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        fibril_mutex_unlock(&d->lock);

        return EOK;
}

/** Issue ATAPI Inquiry.
 *
 * @param dev_idx       Device index (0 or 1)
 * @param obuf          Buffer for storing inquiry data read from device
 * @param obuf_size     Size of obuf in bytes
 *
 * @return EOK on success, EIO on error.
 */
static int ata_pcmd_inquiry(int dev_idx, void *obuf, size_t obuf_size)
{
        ata_pcmd_inquiry_t cp;
        int rc;

        memset(&cp, 0, sizeof(cp));

        cp.opcode = PCMD_INQUIRY;
        cp.alloc_len = min(obuf_size, 0xff); /* Allocation length */

        rc = ata_cmd_packet(0, &cp, sizeof(cp), obuf, obuf_size);
        if (rc != EOK)
                return rc;

        return EOK;
}

/** Issue ATAPI read(12) command.
 *
 * Output buffer must be large enough to hold the data, otherwise the
 * function will fail.
 *
 * @param dev_idx       Device index (0 or 1)
 * @param ba            Starting block address
 * @param cnt           Number of blocks to read
 * @param obuf          Buffer for storing inquiry data read from device
 * @param obuf_size     Size of obuf in bytes
 *
 * @return EOK on success, EIO on error.
 */
static int ata_pcmd_read_12(int dev_idx, uint64_t ba, size_t cnt,
    void *obuf, size_t obuf_size)
{
        ata_pcmd_read_12_t cp;
        int rc;

        if (ba > UINT32_MAX)
                return EINVAL;

        memset(&cp, 0, sizeof(cp));

        cp.opcode = PCMD_READ_12;
        cp.ba = host2uint32_t_be(ba);
        cp.nblocks = host2uint32_t_be(cnt);

        rc = ata_cmd_packet(0, &cp, sizeof(cp), obuf, obuf_size);
        if (rc != EOK)
                return rc;

        return EOK;
}

/** Read a physical from the device.
 *
 * @param disk_id       Device index (0 or 1)
 * @param ba            Address the first block.
 * @param cnt           Number of blocks to transfer.
 * @param buf           Buffer for holding the data.
 *
 * @return EOK on success, EIO on error.
 */
static int ata_rcmd_read(int disk_id, uint64_t ba, size_t blk_cnt,
    void *buf)
{
        size_t i;
        uint16_t data;
        uint8_t status;
        uint8_t drv_head;
        disk_t *d;
        block_coord_t bc;

        d = &disk[disk_id];
        
        /* Silence warning. */
        memset(&bc, 0, sizeof(bc));

        /* Compute block coordinates. */
        if (coord_calc(d, ba, &bc) != EOK)
                return EINVAL;

        /* New value for Drive/Head register */
        drv_head =
            ((disk_id != 0) ? DHR_DRV : 0) |
            ((d->amode != am_chs) ? DHR_LBA : 0) |
            (bc.h & 0x0f);

        fibril_mutex_lock(&d->lock);

        /* Program a Read Sectors operation. */

        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        pio_write_8(&cmd->drive_head, drv_head);

        if (wait_status(SR_DRDY, ~SR_BSY, NULL, TIMEOUT_DRDY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Program block coordinates into the device. */
        coord_sc_program(&bc, 1);

        pio_write_8(&cmd->command, d->amode == am_lba48 ?
            CMD_READ_SECTORS_EXT : CMD_READ_SECTORS);

        if (wait_status(0, ~SR_BSY, &status, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        if ((status & SR_DRQ) != 0) {
                /* Read data from the device buffer. */

                for (i = 0; i < disk[disk_id].block_size / 2; i++) {
                        data = pio_read_16(&cmd->data_port);
                        ((uint16_t *) buf)[i] = data;
                }
        }

        if ((status & SR_ERR) != 0)
                return EIO;

        fibril_mutex_unlock(&d->lock);
        return EOK;
}

/** Write a physical block to the device.
 *
 * @param disk_id       Device index (0 or 1)
 * @param ba            Address of the first block.
 * @param cnt           Number of blocks to transfer.
 * @param buf           Buffer holding the data to write.
 *
 * @return EOK on success, EIO on error.
 */
static int ata_rcmd_write(int disk_id, uint64_t ba, size_t cnt,
    const void *buf)
{
        size_t i;
        uint8_t status;
        uint8_t drv_head;
        disk_t *d;
        block_coord_t bc;

        d = &disk[disk_id];
        
        /* Silence warning. */
        memset(&bc, 0, sizeof(bc));

        /* Compute block coordinates. */
        if (coord_calc(d, ba, &bc) != EOK)
                return EINVAL;

        /* New value for Drive/Head register */
        drv_head =
            ((disk_id != 0) ? DHR_DRV : 0) |
            ((d->amode != am_chs) ? DHR_LBA : 0) |
            (bc.h & 0x0f);

        fibril_mutex_lock(&d->lock);

        /* Program a Write Sectors operation. */

        if (wait_status(0, ~SR_BSY, NULL, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        pio_write_8(&cmd->drive_head, drv_head);

        if (wait_status(SR_DRDY, ~SR_BSY, NULL, TIMEOUT_DRDY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        /* Program block coordinates into the device. */
        coord_sc_program(&bc, 1);

        pio_write_8(&cmd->command, d->amode == am_lba48 ?
            CMD_WRITE_SECTORS_EXT : CMD_WRITE_SECTORS);

        if (wait_status(0, ~SR_BSY, &status, TIMEOUT_BSY) != EOK) {
                fibril_mutex_unlock(&d->lock);
                return EIO;
        }

        if ((status & SR_DRQ) != 0) {
                /* Write data to the device buffer. */

                for (i = 0; i < disk[disk_id].block_size / 2; i++) {
                        pio_write_16(&cmd->data_port, ((uint16_t *) buf)[i]);
                }
        }

        fibril_mutex_unlock(&d->lock);

        if (status & SR_ERR)
                return EIO;

        return EOK;
}

/** Calculate block coordinates.
 *
 * Calculates block coordinates in the best coordinate system supported
 * by the device. These can be later programmed into the device using
 * @c coord_sc_program().
 *
 * @return EOK on success or EINVAL if block index is past end of device.
 */
static int coord_calc(disk_t *d, uint64_t ba, block_coord_t *bc)
{
        uint64_t c;
        uint64_t idx;

        /* Check device bounds. */
        if (ba >= d->blocks)
                return EINVAL;

        bc->amode = d->amode;

        switch (d->amode) {
        case am_chs:
                /* Compute CHS coordinates. */
                c = ba / (d->geom.heads * d->geom.sectors);
                idx = ba % (d->geom.heads * d->geom.sectors);

                bc->cyl_lo = c & 0xff;
                bc->cyl_hi = (c >> 8) & 0xff;
                bc->h      = (idx / d->geom.sectors) & 0x0f;
                bc->sector = (1 + (idx % d->geom.sectors)) & 0xff;
                break;

        case am_lba28:
                /* Compute LBA-28 coordinates. */
                bc->c0 = ba & 0xff;             /* bits 0-7 */
                bc->c1 = (ba >> 8) & 0xff;      /* bits 8-15 */
                bc->c2 = (ba >> 16) & 0xff;     /* bits 16-23 */
                bc->h  = (ba >> 24) & 0x0f;     /* bits 24-27 */
                break;

        case am_lba48:
                /* Compute LBA-48 coordinates. */
                bc->c0 = ba & 0xff;             /* bits 0-7 */
                bc->c1 = (ba >> 8) & 0xff;      /* bits 8-15 */
                bc->c2 = (ba >> 16) & 0xff;     /* bits 16-23 */
                bc->c3 = (ba >> 24) & 0xff;     /* bits 24-31 */
                bc->c4 = (ba >> 32) & 0xff;     /* bits 32-39 */
                bc->c5 = (ba >> 40) & 0xff;     /* bits 40-47 */
                bc->h  = 0;
                break;
        }

        return EOK;
}

/** Program block coordinates and sector count into ATA registers.
 *
 * Note that bc->h must be programmed separately into the device/head register.
 */
static void coord_sc_program(const block_coord_t *bc, uint16_t scnt)
{
        if (bc->amode == am_lba48) {
                /* Write high-order bits. */
                pio_write_8(&cmd->sector_count, scnt >> 8);
                pio_write_8(&cmd->sector_number, bc->c3);
                pio_write_8(&cmd->cylinder_low, bc->c4);
                pio_write_8(&cmd->cylinder_high, bc->c5);
        }

        /* Write low-order bits. */
        pio_write_8(&cmd->sector_count, scnt & 0x00ff);
        pio_write_8(&cmd->sector_number, bc->c0);
        pio_write_8(&cmd->cylinder_low, bc->c1);
        pio_write_8(&cmd->cylinder_high, bc->c2);
}

/** Wait until some status bits are set and some are reset.
 *
 * Example: wait_status(SR_DRDY, ~SR_BSY) waits for SR_DRDY to become
 * set and SR_BSY to become reset.
 *
 * @param set           Combination if bits which must be all set.
 * @param n_reset       Negated combination of bits which must be all reset.
 * @param pstatus       Pointer where to store last read status or NULL.
 * @param timeout       Timeout in 10ms units.
 *
 * @return              EOK on success, EIO on timeout.
 */
static int wait_status(unsigned set, unsigned n_reset, uint8_t *pstatus,
    unsigned timeout)
{
        uint8_t status;
        int cnt;

        status = pio_read_8(&cmd->status);

        /*
         * This is crude, yet simple. First try with 1us delays
         * (most likely the device will respond very fast). If not,
         * start trying every 10 ms.
         */

        cnt = 100;
        while ((status & ~n_reset) != 0 || (status & set) != set) {
                async_usleep(1);
                --cnt;
                if (cnt <= 0) break;

                status = pio_read_8(&cmd->status);
        }

        cnt = timeout;
        while ((status & ~n_reset) != 0 || (status & set) != set) {
                async_usleep(10000);
                --cnt;
                if (cnt <= 0) break;

                status = pio_read_8(&cmd->status);
        }

        if (pstatus)
                *pstatus = status;

        if (cnt == 0)
                return EIO;

        return EOK;
}

/**
 * @}
 */