path: root/lib/sg_pt_linux.c

/*
 * Copyright (c) 2005-2017 Douglas Gilbert.
 * All rights reserved.
 * Use of this source code is governed by a BSD-style
 * license that can be found in the BSD_LICENSE file.
 */

/* sg_pt_linux version 1.32 20171207 */


#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdbool.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>      /* to define 'major' */
#ifndef major
#include <sys/types.h>
#endif


#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <linux/major.h>

#include "sg_pt.h"
#include "sg_lib.h"
#include "sg_linux_inc.h"
#include "sg_pt_linux.h"


#ifdef major
#define SG_DEV_MAJOR major
#else
#ifdef HAVE_LINUX_KDEV_T_H
#include <linux/kdev_t.h>
#endif
#define SG_DEV_MAJOR MAJOR  /* MAJOR() macro faulty if > 255 minors */
#endif

#ifndef BLOCK_EXT_MAJOR
#define BLOCK_EXT_MAJOR 259
#endif

#define DEF_TIMEOUT 60000       /* 60,000 millisecs (60 seconds) */

static const char * linux_host_bytes[] = {
    "DID_OK", "DID_NO_CONNECT", "DID_BUS_BUSY", "DID_TIME_OUT",
    "DID_BAD_TARGET", "DID_ABORT", "DID_PARITY", "DID_ERROR",
    "DID_RESET", "DID_BAD_INTR", "DID_PASSTHROUGH", "DID_SOFT_ERROR",
    "DID_IMM_RETRY", "DID_REQUEUE" /* 0xd */,
    "DID_TRANSPORT_DISRUPTED", "DID_TRANSPORT_FAILFAST",
    "DID_TARGET_FAILURE" /* 0x10 */,
    "DID_NEXUS_FAILURE (reservation conflict)",
    "DID_ALLOC_FAILURE",
    "DID_MEDIUM_ERROR",
};

#define LINUX_HOST_BYTES_SZ \
        (int)(sizeof(linux_host_bytes) / sizeof(linux_host_bytes[0]))

static const char * linux_driver_bytes[] = {
    "DRIVER_OK", "DRIVER_BUSY", "DRIVER_SOFT", "DRIVER_MEDIA",
    "DRIVER_ERROR", "DRIVER_INVALID", "DRIVER_TIMEOUT", "DRIVER_HARD",
    "DRIVER_SENSE"
};

#define LINUX_DRIVER_BYTES_SZ \
    (int)(sizeof(linux_driver_bytes) / sizeof(linux_driver_bytes[0]))

#if 0
static const char * linux_driver_suggests[] = {
    "SUGGEST_OK", "SUGGEST_RETRY", "SUGGEST_ABORT", "SUGGEST_REMAP",
    "SUGGEST_DIE", "UNKNOWN","UNKNOWN","UNKNOWN",
    "SUGGEST_SENSE"
};

#define LINUX_DRIVER_SUGGESTS_SZ \
    (int)(sizeof(linux_driver_suggests) / sizeof(linux_driver_suggests[0]))
#endif

/*
 * These defines are for constants that should be visible in the
 * /usr/include/scsi directory (brought in by sg_linux_inc.h).
 * Redefined and aliased here to decouple this code from
 * sg_io_linux.h  N.B. the SUGGEST_* constants are no longer used.
 */
#ifndef DRIVER_MASK
#define DRIVER_MASK 0x0f
#endif
#ifndef SUGGEST_MASK
#define SUGGEST_MASK 0xf0
#endif
#ifndef DRIVER_SENSE
#define DRIVER_SENSE 0x08
#endif
#define SG_LIB_DRIVER_MASK      DRIVER_MASK
#define SG_LIB_SUGGEST_MASK     SUGGEST_MASK
#define SG_LIB_DRIVER_SENSE    DRIVER_SENSE

bool sg_bsg_nvme_char_major_checked = false;
int sg_bsg_major = 0;
volatile int sg_nvme_char_major = 0;

long sg_lin_page_size = 4096;   /* default, overridden with correct value */


#if defined(__GNUC__) || defined(__clang__)
static int pr2ws(const char * fmt, ...)
        __attribute__ ((format (printf, 1, 2)));
#else
static int pr2ws(const char * fmt, ...);
#endif


static int
pr2ws(const char * fmt, ...)
{
    va_list args;
    int n;

    va_start(args, fmt);
    n = vfprintf(sg_warnings_strm ? sg_warnings_strm : stderr, fmt, args);
    va_end(args);
    return n;
}

/* This function only needs to be called once (unless a NVMe controller
 * can be hot-plugged into system in which case it should be called
 * (again) after that event). */
void
sg_find_bsg_nvme_char_major(int verbose)
{
    bool got_one = false;
    int n;
    const char * proc_devices = "/proc/devices";
    char * cp;
    FILE *fp;
    char a[128];
    char b[128];

    sg_lin_page_size = sysconf(_SC_PAGESIZE);
    if (NULL == (fp = fopen(proc_devices, "r"))) {
        if (verbose)
            pr2ws("fopen %s failed: %s\n", proc_devices, strerror(errno));
        return;
    }
    while ((cp = fgets(b, sizeof(b), fp))) {
        if ((1 == sscanf(b, "%126s", a)) &&
            (0 == memcmp(a, "Character", 9)))
            break;
    }
    while (cp && (cp = fgets(b, sizeof(b), fp))) {
        if (2 == sscanf(b, "%d %126s", &n, a)) {
            if (0 == strcmp("bsg", a)) {
                sg_bsg_major = n;
                if (got_one)
                    break;
                got_one = true;
            } else if (0 == strcmp("nvme", a)) {
                sg_nvme_char_major = n;
                if (got_one)
                    break;
                got_one = true;
            }
        } else
            break;
    }
    if (verbose > 3) {
        if (cp) {
            if (sg_bsg_major > 0)
                pr2ws("found sg_bsg_major=%d\n", sg_bsg_major);
            if (sg_nvme_char_major > 0)
                pr2ws("found sg_nvme_char_major=%d\n", sg_nvme_char_major);
        } else
            pr2ws("found no bsg not nvme char device in %s\n", proc_devices);
    }
    fclose(fp);
}

/* Assumes that sg_find_bsg_nvme_char_major() has already been called. Returns
 * true if dev_fd is a scsi generic pass-through device. If yields
 * *is_nvme_p = true with *nsid_p = 0 then dev_fd is a NVMe char device.
 * If yields *nsid_p > 0 then dev_fd is a NVMe block device. */
static bool
check_file_type(int dev_fd, struct stat * dev_statp, bool * is_bsg_p,
                bool * is_nvme_p, uint32_t * nsid_p, int * os_err_p,
                int verbose)
{
    bool is_nvme = false;
    bool is_sg = false;
    bool is_bsg = false;
    bool is_block = false;
    int os_err = 0;
    int major_num;
    uint32_t nsid = 0;          /* invalid NSID */

    if (dev_fd >= 0) {
        if (fstat(dev_fd, dev_statp) < 0) {
            os_err = errno;
            if (verbose)
                pr2ws("%s: fstat() failed: %s (errno=%d)\n", __func__,
                      safe_strerror(os_err), os_err);
            goto skip_out;
        }
        major_num = (int)SG_DEV_MAJOR(dev_statp->st_rdev);
        if (S_ISCHR(dev_statp->st_mode)) {
            if (SCSI_GENERIC_MAJOR == major_num)
                is_sg = true;
            else if (sg_bsg_major == major_num)
                is_bsg = true;
            else if (sg_nvme_char_major == major_num)
                is_nvme = true;
        } else if (S_ISBLK(dev_statp->st_mode)) {
            is_block = true;
            if (BLOCK_EXT_MAJOR == major_num) {
                is_nvme = true;
                nsid = ioctl(dev_fd, NVME_IOCTL_ID, NULL);
                if (SG_NVME_BROADCAST_NSID == nsid) {  /* means ioctl error */
                    os_err = errno;
                    if (verbose)
                        pr2ws("%s: ioctl(NVME_IOCTL_ID) failed: %s "
                              "(errno=%d)\n", __func__, safe_strerror(os_err),
                              os_err);
                } else
                    os_err = 0;
            }
        }
    } else {
        os_err = EBADF;
        if (verbose)
            pr2ws("%s: invalid file descriptor (%d)\n", __func__, dev_fd);
    }
skip_out:
    if (verbose > 3) {
        pr2ws("%s: file descriptor is ", __func__);
        if (is_sg)
            pr2ws("sg device\n");
        else if (is_bsg)
            pr2ws("bsg device\n");
        else if (is_nvme && (0 == nsid))
            pr2ws("NVMe char device\n");
        else if (is_nvme)
            pr2ws("NVMe block device, nsid=%lld\n",
                  ((uint32_t)-1 == nsid) ? -1LL : (long long)nsid);
        else if (is_block)
            pr2ws("block device\n");
        else
            pr2ws("undetermined device, could be regular file\n");
    }
    if (is_bsg_p)
        *is_bsg_p = is_bsg;
    if (is_nvme_p)
        *is_nvme_p = is_nvme;
    if (nsid_p)
        *nsid_p = nsid;
    if (os_err_p)
        *os_err_p = os_err;
    return is_sg;
}

/* Assumes dev_fd is an "open" file handle associated with device_name. If
 * the implementation (possibly for one OS) cannot determine from dev_fd if
 * a SCSI or NVMe pass-through is referenced, then it might guess based on
 * device_name. Returns 1 if SCSI generic pass-though device, returns 2 if
 * secondary SCSI pass-through device (in Linux a bsg device); returns 3 is
 * char NVMe device (i.e. no NSID); returns 4 if block NVMe device (includes
 * NSID), or 0 if something else (e.g. ATA block device) or dev_fd < 0.
 * If error, returns negated errno (operating system) value. */
int
check_pt_file_handle(int dev_fd, const char * device_name, int verbose)
{
    if (verbose > 4)
        pr2ws("%s: dev_fd=%d, device_name: %s\n", __func__, dev_fd,
              device_name);
    /* Linux doesn't need device_name to determine which pass-through */
    if (! sg_bsg_nvme_char_major_checked) {
        sg_bsg_nvme_char_major_checked = true;
        sg_find_bsg_nvme_char_major(verbose);
    }
    if (dev_fd >= 0) {
        bool is_sg, is_bsg, is_nvme;
        int err;
        uint32_t nsid;
        struct stat a_stat;

        is_sg = check_file_type(dev_fd, &a_stat, &is_bsg, &is_nvme, &nsid,
                                &err, verbose);
        if (err)
            return -err;
        else if (is_sg)
            return 1;
        else if (is_bsg)
            return 2;
        else if (is_nvme && (0 == nsid))
            return 3;
        else if (is_nvme)
            return 4;
        else
            return 0;
    } else
        return 0;
}

/*
 * We make a runtime decision whether to use the sg v3 interface or the sg
 * v4 interface (currently exclusively used by the bsg driver). If all the
 * following are true we use sg v4 which is only currently supported on bsg
 * device nodes:
 *   a) there is a bsg entry in the /proc/devices file
 *   b) the device node given to scsi_pt_open() is a char device
 *   c) the char major number of the device node given to scsi_pt_open()
 *      matches the char major number of the bsg entry in /proc/devices
 * Otherwise the sg v3 interface is used.
 *
 * Note that in either case we prepare the data in a sg v4 structure. If
 * the runtime tests indicate that the v3 interface is needed then
 * do_scsi_pt_v3() transfers the input data into a v3 structure and
 * then the output data is transferred back into a sg v4 structure.
 * That implementation detail could change in the future.
 *
 * [20120806] Only use MAJOR() macro in kdev_t.h if that header file is
 * available and major() macro [N.B. lower case] is not available.
 */


#ifdef major
#define SG_DEV_MAJOR major
#else
#ifdef HAVE_LINUX_KDEV_T_H
#include <linux/kdev_t.h>
#endif
#define SG_DEV_MAJOR MAJOR  /* MAJOR() macro faulty if > 255 minors */
#endif


/* Returns >= 0 if successful. If error in Unix returns negated errno. */
int
scsi_pt_open_device(const char * device_name, bool read_only, int verbose)
{
    int oflags = O_NONBLOCK;

    oflags |= (read_only ? O_RDONLY : O_RDWR);
    return scsi_pt_open_flags(device_name, oflags, verbose);
}

/* Similar to scsi_pt_open_device() but takes Unix style open flags OR-ed */
/* together. The 'flags' argument is advisory and may be ignored. */
/* Returns >= 0 if successful, otherwise returns negated errno. */
int
scsi_pt_open_flags(const char * device_name, int flags, int verbose)
{
    int fd;

    if (! sg_bsg_nvme_char_major_checked) {
        sg_bsg_nvme_char_major_checked = true;
        sg_find_bsg_nvme_char_major(verbose);
    }
    if (verbose > 1) {
        pr2ws("open %s with flags=0x%x\n", device_name, flags);
    }
    fd = open(device_name, flags);
    if (fd < 0) {
        fd = -errno;
        if (verbose > 1)
            pr2ws("%s: open(%s, 0x%x) failed: %s\n", __func__, device_name,
                  flags, safe_strerror(-fd));
    }
    return fd;
}

/* Returns 0 if successful. If error in Unix returns negated errno. */
int
scsi_pt_close_device(int device_fd)
{
    int res;

    res = close(device_fd);
    if (res < 0)
        res = -errno;
    return res;
}


/* Caller should additionally call get_scsi_pt_os_err() after this call */
struct sg_pt_base *
construct_scsi_pt_obj_with_fd(int dev_fd, int verbose)
{
    int err;
    struct sg_pt_linux_scsi * ptp;

    /* The following 2 lines are temporary. It is to avoid a NULL pointer
     * crash when an old utility is used with a newer library built after
     * the sg_warnings_strm cleanup */
    if (NULL == sg_warnings_strm)
        sg_warnings_strm = stderr;

    ptp = (struct sg_pt_linux_scsi *)
          calloc(1, sizeof(struct sg_pt_linux_scsi));
    if (ptp) {
        err = set_pt_file_handle((struct sg_pt_base *)ptp, dev_fd, verbose);
        if ((0 == err) && (! ptp->is_nvme)) {
            ptp->io_hdr.guard = 'Q';
#ifdef BSG_PROTOCOL_SCSI
            ptp->io_hdr.protocol = BSG_PROTOCOL_SCSI;
#endif
#ifdef BSG_SUB_PROTOCOL_SCSI_CMD
            ptp->io_hdr.subprotocol = BSG_SUB_PROTOCOL_SCSI_CMD;
#endif
        }
    } else if (verbose)
        pr2ws("%s: calloc() failed, out of memory?\n", __func__);

    return (struct sg_pt_base *)ptp;
}

struct sg_pt_base *
construct_scsi_pt_obj()
{
    return construct_scsi_pt_obj_with_fd(-1 /* dev_fd */, 0 /* verbose */);
}

void
destruct_scsi_pt_obj(struct sg_pt_base * vp)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp)
        free(ptp);
}

/* Remembers previous device file descriptor */
void
clear_scsi_pt_obj(struct sg_pt_base * vp)
{
    bool is_sg, is_bsg, is_nvme;
    int fd, nvme_nsid;
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp) {
        fd = ptp->dev_fd;
        is_sg = ptp->is_sg;
        is_bsg = ptp->is_bsg;
        is_nvme = ptp->is_nvme;
        nvme_nsid = ptp->nvme_nsid;
        memset(ptp, 0, sizeof(struct sg_pt_linux_scsi));
        ptp->io_hdr.guard = 'Q';
#ifdef BSG_PROTOCOL_SCSI
        ptp->io_hdr.protocol = BSG_PROTOCOL_SCSI;
#endif
#ifdef BSG_SUB_PROTOCOL_SCSI_CMD
        ptp->io_hdr.subprotocol = BSG_SUB_PROTOCOL_SCSI_CMD;
#endif
        ptp->dev_fd = fd;
        ptp->is_sg = is_sg;
        ptp->is_bsg = is_bsg;
        ptp->is_nvme = is_nvme;
        ptp->nvme_nsid = nvme_nsid;
    }
}

/* Forget any previous dev_fd and install the one given. May attempt to
 * find file type (e.g. if pass-though) from OS so there could be an error.
 * Returns 0 for success or the same value as get_scsi_pt_os_err()
 * will return. dev_fd should be >= 0 for a valid file handle or -1 . */
int
set_pt_file_handle(struct sg_pt_base * vp, int dev_fd, int verbose)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;
    struct stat a_stat;

    if (! sg_bsg_nvme_char_major_checked) {
        sg_bsg_nvme_char_major_checked = true;
        sg_find_bsg_nvme_char_major(verbose);
    }
    ptp->dev_fd = dev_fd;
    if (dev_fd >= 0)
        ptp->is_sg = check_file_type(dev_fd, &a_stat, &ptp->is_bsg,
                                     &ptp->is_nvme, &ptp->nvme_nsid,
                                     &ptp->os_err, verbose);
    else {
        ptp->is_sg = false;
        ptp->is_bsg = false;
        ptp->is_nvme = false;
        ptp->nvme_nsid = 0;
        ptp->os_err = 0;
    }
    return ptp->os_err;
}

/* Valid file handles (which is the return value) are >= 0 . Returns -1
 * if there is no valid file handle. */
int
get_pt_file_handle(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->dev_fd;
}

void
set_scsi_pt_cdb(struct sg_pt_base * vp, const unsigned char * cdb,
                int cdb_len)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp->io_hdr.request)
        ++ptp->in_err;
    ptp->io_hdr.request = (__u64)(sg_uintptr_t)cdb;
    ptp->io_hdr.request_len = cdb_len;
}

void
set_scsi_pt_sense(struct sg_pt_base * vp, unsigned char * sense,
                  int max_sense_len)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp->io_hdr.response)
        ++ptp->in_err;
    memset(sense, 0, max_sense_len);
    ptp->io_hdr.response = (__u64)(sg_uintptr_t)sense;
    ptp->io_hdr.max_response_len = max_sense_len;
}

/* Setup for data transfer from device */
void
set_scsi_pt_data_in(struct sg_pt_base * vp, unsigned char * dxferp,
                    int dxfer_ilen)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp->io_hdr.din_xferp)
        ++ptp->in_err;
    if (dxfer_ilen > 0) {
        ptp->io_hdr.din_xferp = (__u64)(sg_uintptr_t)dxferp;
        ptp->io_hdr.din_xfer_len = dxfer_ilen;
    }
}

/* Setup for data transfer toward device */
void
set_scsi_pt_data_out(struct sg_pt_base * vp, const unsigned char * dxferp,
                     int dxfer_olen)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (ptp->io_hdr.dout_xferp)
        ++ptp->in_err;
    if (dxfer_olen > 0) {
        ptp->io_hdr.dout_xferp = (__u64)(sg_uintptr_t)dxferp;
        ptp->io_hdr.dout_xfer_len = dxfer_olen;
    }
}

void
set_pt_metadata_xfer(struct sg_pt_base * vp, unsigned char * dxferp,
                     uint32_t dxfer_len, bool out_true)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (dxfer_len > 0) {
        ptp->mdxferp = dxferp;
        ptp->mdxfer_len = dxfer_len;
        ptp->mdxfer_out = out_true;
    }
}

void
set_scsi_pt_packet_id(struct sg_pt_base * vp, int pack_id)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    ptp->io_hdr.spare_in = pack_id;
}

void
set_scsi_pt_tag(struct sg_pt_base * vp, uint64_t tag)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    ptp->io_hdr.request_tag = tag;
}

/* Note that task management function codes are transport specific */
void
set_scsi_pt_task_management(struct sg_pt_base * vp, int tmf_code)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    ptp->io_hdr.subprotocol = 1;        /* SCSI task management function */
    ptp->tmf_request[0] = (unsigned char)tmf_code;      /* assume it fits */
    ptp->io_hdr.request = (__u64)(sg_uintptr_t)(&(ptp->tmf_request[0]));
    ptp->io_hdr.request_len = 1;
}

void
set_scsi_pt_task_attr(struct sg_pt_base * vp, int attribute, int priority)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    ptp->io_hdr.request_attr = attribute;
    ptp->io_hdr.request_priority = priority;
}

#ifndef BSG_FLAG_Q_AT_TAIL
#define BSG_FLAG_Q_AT_TAIL 0x10
#endif
#ifndef BSG_FLAG_Q_AT_HEAD
#define BSG_FLAG_Q_AT_HEAD 0x20
#endif

/* Need this later if translated to v3 interface */
#ifndef SG_FLAG_Q_AT_TAIL
#define SG_FLAG_Q_AT_TAIL 0x10
#endif
#ifndef SG_FLAG_Q_AT_HEAD
#define SG_FLAG_Q_AT_HEAD 0x20
#endif

void
set_scsi_pt_flags(struct sg_pt_base * vp, int flags)
{
    struct sg_pt_linux_scsi * ptp = &vp->impl;

    /* default action of bsg driver (sg v4) is QUEUE_AT_HEAD */
    /* default action of block layer SG_IO ioctl is QUEUE_AT_TAIL */
    if (SCSI_PT_FLAGS_QUEUE_AT_HEAD & flags) {  /* favour AT_HEAD */
        ptp->io_hdr.flags |= BSG_FLAG_Q_AT_HEAD;
        ptp->io_hdr.flags &= ~BSG_FLAG_Q_AT_TAIL;
    } else if (SCSI_PT_FLAGS_QUEUE_AT_TAIL & flags) {
        ptp->io_hdr.flags |= BSG_FLAG_Q_AT_TAIL;
        ptp->io_hdr.flags &= ~BSG_FLAG_Q_AT_HEAD;
    }
}

/* N.B. Returns din_resid and ignores dout_resid */
int
get_scsi_pt_resid(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (NULL == ptp)
        return 0;
    return ptp->is_nvme ? 0 : ptp->io_hdr.din_resid;
}

int
get_scsi_pt_status_response(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (NULL == ptp)
        return 0;
    return (int)(ptp->is_nvme ? ptp->nvme_status :
                                ptp->io_hdr.device_status);
    return ptp->io_hdr.device_status;
}

uint32_t
get_pt_result(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    if (NULL == ptp)
        return 0;
    return ptp->is_nvme ? ptp->nvme_status :
                          ptp->io_hdr.device_status;
}

int
get_scsi_pt_sense_len(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->io_hdr.response_len;
}

int
get_scsi_pt_duration_ms(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->io_hdr.duration;
}

int
get_scsi_pt_transport_err(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->io_hdr.transport_status;
}

/* Returns b which will contain a null char terminated string (if
 * max_b_len > 0). Combined driver and transport (called "host" in Linux
 * kernel) statuses */
char *
get_scsi_pt_transport_err_str(const struct sg_pt_base * vp, int max_b_len,
                              char * b)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;
    int ds = ptp->io_hdr.driver_status;
    int hs = ptp->io_hdr.transport_status;
    int n, m;
    char * cp = b;
    int driv;
    const char * driv_cp = "invalid";

    if (max_b_len < 1)
        return b;
    m = max_b_len;
    n = 0;
    if (hs) {
        if ((hs < 0) || (hs >= LINUX_HOST_BYTES_SZ))
            n = snprintf(cp, m, "Host_status=0x%02x is invalid\n", hs);
        else
            n = snprintf(cp, m, "Host_status=0x%02x [%s]\n", hs,
                         linux_host_bytes[hs]);
    }
    m -= n;
    if (m < 1) {
        b[max_b_len - 1] = '\0';
        return b;
    }
    cp += n;
    driv = ds & SG_LIB_DRIVER_MASK;
    if (driv < LINUX_DRIVER_BYTES_SZ)
        driv_cp = linux_driver_bytes[driv];
#if 0
    sugg = (ds & SG_LIB_SUGGEST_MASK) >> 4;
    if (sugg < LINUX_DRIVER_SUGGESTS_SZ)
        sugg_cp = linux_driver_suggests[sugg];
#endif
    n = snprintf(cp, m, "Driver_status=0x%02x [%s]\n", ds, driv_cp);
    m -= n;
    if (m < 1)
        b[max_b_len - 1] = '\0';
    return b;
}

int
get_scsi_pt_result_category(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;
    int dr_st = ptp->io_hdr.driver_status & SG_LIB_DRIVER_MASK;
    int scsi_st = ptp->io_hdr.device_status & 0x7e;

    if (ptp->os_err)
        return SCSI_PT_RESULT_OS_ERR;
    else if (ptp->io_hdr.transport_status)
        return SCSI_PT_RESULT_TRANSPORT_ERR;
    else if (dr_st && (SG_LIB_DRIVER_SENSE != dr_st))
        return SCSI_PT_RESULT_TRANSPORT_ERR;
    else if ((SG_LIB_DRIVER_SENSE == dr_st) ||
             (SAM_STAT_CHECK_CONDITION == scsi_st) ||
             (SAM_STAT_COMMAND_TERMINATED == scsi_st))
        return SCSI_PT_RESULT_SENSE;
    else if (scsi_st)
        return SCSI_PT_RESULT_STATUS;
    else
        return SCSI_PT_RESULT_GOOD;
}

int
get_scsi_pt_os_err(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->os_err;
}

char *
get_scsi_pt_os_err_str(const struct sg_pt_base * vp, int max_b_len, char * b)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;
    const char * cp;

    cp = safe_strerror(ptp->os_err);
    strncpy(b, cp, max_b_len);
    if ((int)strlen(cp) >= max_b_len)
        b[max_b_len - 1] = '\0';
    return b;
}

bool
pt_device_is_nvme(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->is_nvme;
}

/* If a NVMe block device (which includes the NSID) handle is associated
 * with 'vp', then its NSID is returned (values range from 0x1 to
 * 0xffffffe). Otherwise 0 is returned. */
uint32_t
get_pt_nvme_nsid(const struct sg_pt_base * vp)
{
    const struct sg_pt_linux_scsi * ptp = &vp->impl;

    return ptp->nvme_nsid;
}

/* Executes SCSI command using sg v3 interface */
static int
do_scsi_pt_v3(struct sg_pt_linux_scsi * ptp, int fd, int time_secs,
              int verbose)
{
    struct sg_io_hdr v3_hdr;

    memset(&v3_hdr, 0, sizeof(v3_hdr));
    /* convert v4 to v3 header */
    v3_hdr.interface_id = 'S';
    v3_hdr.dxfer_direction = SG_DXFER_NONE;
    v3_hdr.cmdp = (unsigned char *)(long)ptp->io_hdr.request;
    v3_hdr.cmd_len = (unsigned char)ptp->io_hdr.request_len;
    if (ptp->io_hdr.din_xfer_len > 0) {
        if (ptp->io_hdr.dout_xfer_len > 0) {
            if (verbose)
                pr2ws("sgv3 doesn't support bidi\n");
            return SCSI_PT_DO_BAD_PARAMS;
        }
        v3_hdr.dxferp = (void *)(long)ptp->io_hdr.din_xferp;
        v3_hdr.dxfer_len = (unsigned int)ptp->io_hdr.din_xfer_len;
        v3_hdr.dxfer_direction =  SG_DXFER_FROM_DEV;
    } else if (ptp->io_hdr.dout_xfer_len > 0) {
        v3_hdr.dxferp = (void *)(long)ptp->io_hdr.dout_xferp;
        v3_hdr.dxfer_len = (unsigned int)ptp->io_hdr.dout_xfer_len;
        v3_hdr.dxfer_direction =  SG_DXFER_TO_DEV;
    }
    if (ptp->io_hdr.response && (ptp->io_hdr.max_response_len > 0)) {
        v3_hdr.sbp = (unsigned char *)(long)ptp->io_hdr.response;
        v3_hdr.mx_sb_len = (unsigned char)ptp->io_hdr.max_response_len;
    }
    v3_hdr.pack_id = (int)ptp->io_hdr.spare_in;
    if (BSG_FLAG_Q_AT_HEAD & ptp->io_hdr.flags)
        v3_hdr.flags |= SG_FLAG_Q_AT_HEAD;      /* favour AT_HEAD */
    else if (BSG_FLAG_Q_AT_TAIL & ptp->io_hdr.flags)
        v3_hdr.flags |= SG_FLAG_Q_AT_TAIL;

    if (NULL == v3_hdr.cmdp) {
        if (verbose)
            pr2ws("No SCSI command (cdb) given\n");
        return SCSI_PT_DO_BAD_PARAMS;
    }
    /* io_hdr.timeout is in milliseconds, if greater than zero */
    v3_hdr.timeout = ((time_secs > 0) ? (time_secs * 1000) : DEF_TIMEOUT);
    /* Finally do the v3 SG_IO ioctl */
    if (ioctl(fd, SG_IO, &v3_hdr) < 0) {
        ptp->os_err = errno;
        if (verbose > 1)
            pr2ws("ioctl(SG_IO v3) failed: %s (errno=%d)\n",
                  safe_strerror(ptp->os_err), ptp->os_err);
        return -ptp->os_err;
    }
    ptp->io_hdr.device_status = (__u32)v3_hdr.status;
    ptp->io_hdr.driver_status = (__u32)v3_hdr.driver_status;
    ptp->io_hdr.transport_status = (__u32)v3_hdr.host_status;
    ptp->io_hdr.response_len = (__u32)v3_hdr.sb_len_wr;
    ptp->io_hdr.duration = (__u32)v3_hdr.duration;
    ptp->io_hdr.din_resid = (__s32)v3_hdr.resid;
    /* v3_hdr.info not passed back since no mapping defined (yet) */
    return 0;
}

/* Executes SCSI command (or at least forwards it to lower layers).
 * Returns 0 for success, negative numbers are negated 'errno' values from
 * OS system calls. Positive return values are errors from this package. */
int
do_scsi_pt(struct sg_pt_base * vp, int fd, int time_secs, int verbose)
{
    int err;
    struct sg_pt_linux_scsi * ptp = &vp->impl;
    bool have_checked_for_type = (ptp->dev_fd >= 0);

    if (! sg_bsg_nvme_char_major_checked) {
        sg_bsg_nvme_char_major_checked = true;
        sg_find_bsg_nvme_char_major(verbose);
    }
    if (ptp->in_err) {
        if (verbose)
            pr2ws("Replicated or unused set_scsi_pt... functions\n");
        return SCSI_PT_DO_BAD_PARAMS;
    }
    if (fd >= 0) {
        if ((ptp->dev_fd >= 0) && (fd != ptp->dev_fd)) {
            if (verbose)
                pr2ws("%s: file descriptor given to create() and here "
                      "differ\n", __func__);
            return SCSI_PT_DO_BAD_PARAMS;
        }
        ptp->dev_fd = fd;
    } else if (ptp->dev_fd < 0) {
        if (verbose)
            pr2ws("%s: invalid file descriptors\n", __func__);
        return SCSI_PT_DO_BAD_PARAMS;
    }
    if (! have_checked_for_type) {
        err = set_pt_file_handle(vp, ptp->dev_fd, verbose);
        if (err)
            return -ptp->os_err;
    }
    if (ptp->os_err)
        return -ptp->os_err;
    if (ptp->is_nvme)
        return sg_do_nvme_pt(vp, -1, time_secs, verbose);
    else if (sg_bsg_major <= 0)
        return do_scsi_pt_v3(ptp, fd, time_secs, verbose);
    else if (ptp->is_bsg)
        ; /* drop through to sg v4 implementation */
    else
        return do_scsi_pt_v3(ptp, fd, time_secs, verbose);

    if (! ptp->io_hdr.request) {
        if (verbose)
            pr2ws("No SCSI command (cdb) given (v4)\n");
        return SCSI_PT_DO_BAD_PARAMS;
    }
    /* io_hdr.timeout is in milliseconds */
    ptp->io_hdr.timeout = ((time_secs > 0) ? (time_secs * 1000) :
                                             DEF_TIMEOUT);
#if 0
    /* sense buffer already zeroed */
    if (ptp->io_hdr.response && (ptp->io_hdr.max_response_len > 0)) {
        void * p;

        p = (void *)(long)ptp->io_hdr.response;
        memset(p, 0, ptp->io_hdr.max_response_len);
    }
#endif
    if (ioctl(fd, SG_IO, &ptp->io_hdr) < 0) {
        ptp->os_err = errno;
        if (verbose > 1)
            pr2ws("ioctl(SG_IO v4) failed: %s (errno=%d)\n",
                  safe_strerror(ptp->os_err), ptp->os_err);
        return -ptp->os_err;
    }
    return 0;
}