sun4v/io/ds_snmp.c

	ds_snmp.c revision ece6eed9d93d19d2c26893d5ac4fd2f73b1633dc
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 * sun4v domain services SNMP driver
 */

#include <sys/types.h>
#include <sys/file.h>
#include <sys/errno.h>
#include <sys/open.h>
#include <sys/cred.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <sys/ksynch.h>
#include <sys/modctl.h>
#include <sys/conf.h>
#include <sys/devops.h>
#include <sys/debug.h>
#include <sys/cmn_err.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/ds.h>
#include <sys/ds_snmp.h>

#define DS_SNMP_NAME        "ds_snmp"
#define DS_SNMP_MAX_OPENS   256
#define DS_BITS_IN_UINT64   64
#define DS_MINOR_POOL_SZ    (DS_SNMP_MAX_OPENS / DS_BITS_IN_UINT64)
#define DS_SNMP_MINOR_SHIFT 56
#define DS_SNMP_DBG     if (ds_snmp_debug) printf

typedef struct {
    uint64_t    seq_num;
    uint64_t    type;
} ds_snmp_msg_t;

typedef enum {
    DS_SNMP_REQUEST = 0,
    DS_SNMP_REPLY   = 1,
    DS_SNMP_ERROR = 2
} ds_snmp_msg_type_t;

typedef enum {
    DS_SNMP_READY = 0x0,
    DS_SNMP_REQUESTED = 0x1,
    DS_SNMP_DATA_AVL = 0x2,
    DS_SNMP_DATA_ERR = 0x3
} ds_snmp_flags_t;

/*
 * The single mutex 'lock' protects all the SNMP/DS variables in the state
 * structure.
 *
 * The condition variable 'state_cv' helps serialize write() calls for a
 * single descriptor. When write() is called, it sets a flag to indicate
 * that an SNMP request has been made to the agent. No more write()'s on
 * the same open descriptor will be allowed until this flag is cleared via
 * a matching read(), where the requested packet is consumed on arrival.
 * Read() then wakes up any waiters blocked in write() for sending the next
 * SNMP request to the agent.
 */
typedef struct ds_snmp_state {
    dev_info_t  *dip;
    int     instance;
    dev_t       dev;

    /* SNMP/DS */
    kmutex_t    lock;
    kcondvar_t  state_cv;
    ds_snmp_flags_t state;
    void        *data;
    size_t      data_len;
    uint64_t    req_id;
    uint64_t    last_req_id;
    uint64_t    gencount;
    boolean_t   sc_reset;
} ds_snmp_state_t;


static uint_t       ds_snmp_debug = 0;
static void     *ds_snmp_statep = NULL;
static int      ds_snmp_instance = -1;
static dev_info_t   *ds_snmp_devi = NULL;

/*
 * The ds_snmp_lock mutex protects the following data global to the
 * driver.
 *
 * The ds_snmp_service_cv condition variable is used to resolve the
 * potential race between the registration of snmp service via a
 * ds_cap_init() in attach(), the acknowledgement of this registration
 * at a later time in ds_snmp_reg_handler(), and a possible open() at
 * a time inbetween. The ds_snmp_has_service and ds_snmp_handle are
 * used to indicate whether the registration acknowledgement has happened
 * or not.
 *
 * The ds_snmp_minor_pool[] is a bitmask to allocate and keep track of
 * minor numbers dynamically.
 */
static kmutex_t     ds_snmp_lock;
static kcondvar_t   ds_snmp_service_cv;
static int      ds_snmp_has_service = B_FALSE;
static ds_svc_hdl_t ds_snmp_handle = DS_INVALID_HDL;
static uint64_t     ds_snmp_minor_pool[DS_MINOR_POOL_SZ];   /* bitmask */
static int      ds_snmp_num_opens = 0;

static int ds_snmp_getinfo(dev_info_t *, ddi_info_cmd_t, void *, void **);
static int ds_snmp_attach(dev_info_t *, ddi_attach_cmd_t);
static int ds_snmp_detach(dev_info_t *, ddi_detach_cmd_t);
static int ds_snmp_open(dev_t *, int, int, cred_t *);
static int ds_snmp_close(dev_t, int, int, cred_t *);
static int ds_snmp_read(dev_t, struct uio *, cred_t *);
static int ds_snmp_write(dev_t, struct uio *, cred_t *);
static int ds_snmp_ioctl(dev_t, int, intptr_t, int, cred_t *, int *);

/*
 * DS Callbacks
 */
static void ds_snmp_reg_handler(ds_cb_arg_t, ds_ver_t *, ds_svc_hdl_t);
static void ds_snmp_unreg_handler(ds_cb_arg_t arg);
static void ds_snmp_data_handler(ds_cb_arg_t arg, void *buf, size_t buflen);

/*
 * SNMP DS capability registration
 */
static ds_ver_t ds_snmp_ver_1_0 = { 1, 0 };
static ds_capability_t ds_snmp_cap = {
    "snmp",
    &ds_snmp_ver_1_0,
    1
};

/*
 * SNMP DS Client callback vector
 */
static ds_clnt_ops_t ds_snmp_ops = {
    ds_snmp_reg_handler,    /* ds_reg_cb */
    ds_snmp_unreg_handler,  /* ds_unreg_cb */
    ds_snmp_data_handler,   /* ds_data_cb */
    NULL            /* cb_arg */
};

/*
 * DS SNMP driver Ops Vector
 */
static struct cb_ops ds_snmp_cb_ops = {
    ds_snmp_open,       /* cb_open */
    ds_snmp_close,      /* cb_close */
    nodev,          /* cb_strategy */
    nodev,          /* cb_print */
    nodev,          /* cb_dump */
    ds_snmp_read,       /* cb_read */
    ds_snmp_write,      /* cb_write */
    ds_snmp_ioctl,      /* cb_ioctl */
    nodev,          /* cb_devmap */
    nodev,          /* cb_mmap */
    nodev,          /* cb_segmap */
    nochpoll,       /* cb_chpoll */
    ddi_prop_op,        /* cb_prop_op */
    (struct streamtab *)NULL, /* cb_str */
    D_MP | D_64BIT,     /* cb_flag */
    CB_REV,         /* cb_rev */
    nodev,          /* cb_aread */
    nodev           /* cb_awrite */
};

static struct dev_ops ds_snmp_dev_ops = {
    DEVO_REV,       /* devo_rev */
    0,          /* devo_refcnt */
    ds_snmp_getinfo,    /* devo_getinfo */
    nulldev,        /* devo_identify */
    nulldev,        /* devo_probe */
    ds_snmp_attach,     /* devo_attach */
    ds_snmp_detach,     /* devo_detach */
    nodev,          /* devo_reset */
    &ds_snmp_cb_ops,    /* devo_cb_ops */
    (struct bus_ops *)NULL, /* devo_bus_ops */
    nulldev         /* devo_power */
};

static struct modldrv modldrv = {
    &mod_driverops,
    "Domain Services SNMP Driver 1.0",
    &ds_snmp_dev_ops
};

static struct modlinkage modlinkage = {
    MODREV_1,
    (void *)&modldrv,
    NULL
};

int
_init(void)
{
    int retval;

    mutex_init(&ds_snmp_lock, NULL, MUTEX_DRIVER, NULL);
    cv_init(&ds_snmp_service_cv, NULL, CV_DRIVER, NULL);

    retval = ddi_soft_state_init(&ds_snmp_statep,
        sizeof (ds_snmp_state_t), DS_SNMP_MAX_OPENS);
    if (retval != 0) {
        cv_destroy(&ds_snmp_service_cv);
        mutex_destroy(&ds_snmp_lock);
        return (retval);
    }

    retval = mod_install(&modlinkage);
    if (retval != 0) {
        ddi_soft_state_fini(&ds_snmp_statep);
        cv_destroy(&ds_snmp_service_cv);
        mutex_destroy(&ds_snmp_lock);
    }

    return (retval);
}

int
_info(struct modinfo *modinfop)
{
    return (mod_info(&modlinkage, modinfop));
}

int
_fini(void)
{
    int retval;

    if ((retval = mod_remove(&modlinkage)) != 0)
        return (retval);

    ddi_soft_state_fini(&ds_snmp_statep);

    cv_destroy(&ds_snmp_service_cv);
    mutex_destroy(&ds_snmp_lock);

    return (retval);
}

/*ARGSUSED*/
static int
ds_snmp_getinfo(dev_info_t *dip, ddi_info_cmd_t cmd, void *arg, void **resultp)
{
    ds_snmp_state_t *sp;
    int retval = DDI_FAILURE;

    ASSERT(resultp != NULL);

    switch (cmd) {
    case DDI_INFO_DEVT2DEVINFO:
        sp = ddi_get_soft_state(ds_snmp_statep, getminor((dev_t)arg));
        if (sp != NULL) {
            *resultp = sp->dip;
            retval = DDI_SUCCESS;
        } else
            *resultp = NULL;
        break;

    case DDI_INFO_DEVT2INSTANCE:
        *resultp = (void *)(uintptr_t)getminor((dev_t)arg);
        retval = DDI_SUCCESS;
        break;
    }

    return (retval);
}

static int
ds_snmp_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
    int rv;

    switch (cmd) {
    case DDI_ATTACH:
        if (ds_snmp_instance != -1)
            return (DDI_FAILURE);
        break;

    case DDI_RESUME:
        return (DDI_SUCCESS);

    default:
        return (DDI_FAILURE);
    }

    ds_snmp_instance = ddi_get_instance(dip);
    if (ddi_create_minor_node(dip, DS_SNMP_NAME, S_IFCHR, ds_snmp_instance,
        DDI_PSEUDO, 0) != DDI_SUCCESS) {
        cmn_err(CE_WARN, "%s@%d: Unable to create minor node",
            DS_SNMP_NAME, ds_snmp_instance);
        return (DDI_FAILURE);
    }

    bzero(ds_snmp_minor_pool, DS_MINOR_POOL_SZ * sizeof (uint64_t));

    ds_snmp_ops.cb_arg = dip;
    if ((rv = ds_cap_init(&ds_snmp_cap, &ds_snmp_ops)) != 0) {
        cmn_err(CE_NOTE, "ds_cap_init failed: %d", rv);
        ddi_remove_minor_node(dip, NULL);
        ds_snmp_instance = -1;
        return (DDI_FAILURE);
    }

    ds_snmp_devi = dip;
    ddi_report_dev(dip);

    return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
ds_snmp_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
    switch (cmd) {
    case DDI_DETACH:
        if (ds_snmp_instance == -1)
            return (DDI_FAILURE);
        break;

    case DDI_SUSPEND:
        return (DDI_SUCCESS);

    default:
        return (DDI_FAILURE);
    }

    (void) ds_cap_fini(&ds_snmp_cap);

    ddi_remove_minor_node(ds_snmp_devi, NULL);
    bzero(ds_snmp_minor_pool, DS_MINOR_POOL_SZ * sizeof (uint64_t));

    ds_snmp_instance = -1;
    ds_snmp_devi = NULL;

    return (DDI_SUCCESS);
}

static minor_t
ds_snmp_get_minor(void)
{
    uint64_t    val;
    int     i, ndx;
    minor_t     minor;

    mutex_enter(&ds_snmp_lock);
    for (ndx = 0; ndx < DS_MINOR_POOL_SZ; ndx++) {
        val = ds_snmp_minor_pool[ndx];
        for (i = 0; i < DS_BITS_IN_UINT64; i++) {
            if ((val & 0x1) == 0) {
                ds_snmp_minor_pool[ndx] |= ((uint64_t)1 << i);
                ds_snmp_num_opens++;
                mutex_exit(&ds_snmp_lock);

                minor = ndx * DS_BITS_IN_UINT64 + i + 1;

                return (minor);
            }
            val >>= 1;
        }
    }
    mutex_exit(&ds_snmp_lock);

    return (0);
}

static void
ds_snmp_rel_minor(minor_t minor)
{
    int i, ndx;

    ndx = (minor - 1) / DS_BITS_IN_UINT64;
    i = (minor - 1) % DS_BITS_IN_UINT64;

    ASSERT(ndx < DS_MINOR_POOL_SZ);

    mutex_enter(&ds_snmp_lock);

    ds_snmp_num_opens--;
    ds_snmp_minor_pool[ndx] &= ~((uint64_t)1 << i);

    mutex_exit(&ds_snmp_lock);
}

static boolean_t
ds_snmp_is_open(minor_t minor)
{
    uint64_t    val;
    int     i, ndx;

    ndx = (minor - 1) / DS_BITS_IN_UINT64;
    i = (minor - 1) % DS_BITS_IN_UINT64;

    val = ((uint64_t)1 << i);
    if (ds_snmp_minor_pool[ndx] & val)
        return (B_TRUE);
    else
        return (B_FALSE);
}

static int
ds_snmp_create_state(dev_t *devp)
{
    major_t major;
    minor_t minor;
    ds_snmp_state_t *sp;

    if ((minor = ds_snmp_get_minor()) == 0)
        return (EMFILE);

    if (ddi_soft_state_zalloc(ds_snmp_statep, minor) != DDI_SUCCESS) {
        cmn_err(CE_WARN, "%s@%d: Unable to allocate state",
            DS_SNMP_NAME, minor);
        ds_snmp_rel_minor(minor);
        return (ENOMEM);
    }

    sp = ddi_get_soft_state(ds_snmp_statep, minor);
    if (devp != NULL)
        major = getemajor(*devp);
    else
        major = ddi_driver_major(ds_snmp_devi);

    sp->dev = makedevice(major, minor);
    if (devp != NULL)
        *devp = sp->dev;

    sp->instance = minor;
    sp->data = NULL;
    sp->data_len = 0;
    sp->req_id = 0;
    sp->last_req_id = 0;
    sp->state = DS_SNMP_READY;
    sp->sc_reset = B_FALSE;

    mutex_init(&sp->lock, NULL, MUTEX_DRIVER, NULL);
    cv_init(&sp->state_cv, NULL, CV_DRIVER, NULL);

    return (0);
}

static int
ds_snmp_destroy_state(dev_t dev)
{
    ds_snmp_state_t *sp;
    minor_t minor;

    minor = getminor(dev);

    if ((sp = ddi_get_soft_state(ds_snmp_statep, minor)) == NULL)
        return (ENXIO);

    ASSERT(sp->instance == minor);

    /*
     * If the app has not exited cleanly, the data may not have been
     * read/memory freed, hence take care of that here
     */
    if (sp->data) {
        kmem_free(sp->data, sp->data_len);
    }
    cv_destroy(&sp->state_cv);
    mutex_destroy(&sp->lock);

    ddi_soft_state_free(ds_snmp_statep, minor);
    ds_snmp_rel_minor(minor);

    return (0);
}

/*ARGSUSED*/
static int
ds_snmp_open(dev_t *devp, int flag, int otyp, cred_t *credp)
{

    if (otyp != OTYP_CHR)
        return (EINVAL);

    if (ds_snmp_instance == -1)
        return (ENXIO);

    /*
     * Avoid possible race condition - ds service may not be there yet
     */
    mutex_enter(&ds_snmp_lock);
    while (ds_snmp_has_service == B_FALSE) {
        if (cv_wait_sig(&ds_snmp_service_cv, &ds_snmp_lock) == 0) {
            mutex_exit(&ds_snmp_lock);
            return (EINTR);
        }
    }
    mutex_exit(&ds_snmp_lock);

    return (ds_snmp_create_state(devp));
}


/*ARGSUSED*/
static int
ds_snmp_close(dev_t dev, int flag, int otyp, cred_t *credp)
{
    if (otyp != OTYP_CHR)
        return (EINVAL);

    if (ds_snmp_instance == -1)
        return (ENXIO);

    if (ds_snmp_handle == DS_INVALID_HDL)
        return (EIO);

    return (ds_snmp_destroy_state(dev));
}

/*ARGSUSED*/
static int
ds_snmp_read(dev_t dev, struct uio *uiop, cred_t *credp)
{
    ds_snmp_state_t *sp;
    minor_t minor;
    size_t len;
    int retval;
    caddr_t tmpbufp = (caddr_t)NULL;

    /*
     * Given that now we can have sc resets happening at any
     * time, it is possible that it happened since the last time
     * we issued a read, write or ioctl.  If so, we need to wait
     * for the unreg-reg pair to complete before we can do
     * anything.
     */
    mutex_enter(&ds_snmp_lock);
    while (ds_snmp_has_service == B_FALSE) {
        DS_SNMP_DBG("ds_snmp_read: waiting for service\n");
        if (cv_wait_sig(&ds_snmp_service_cv, &ds_snmp_lock) == 0) {
            mutex_exit(&ds_snmp_lock);
            return (EINTR);
        }
    }
    mutex_exit(&ds_snmp_lock);

    if ((len = uiop->uio_resid) == 0)
        return (0);

    minor = getminor(dev);
    if ((sp = ddi_get_soft_state(ds_snmp_statep, minor)) == NULL)
        return (ENXIO);

    mutex_enter(&sp->lock);

    if (sp->sc_reset == B_TRUE) {
        mutex_exit(&sp->lock);
        return (ECANCELED);
    }

    /*
     * Block or bail if there is no SNMP data
     */
    if (sp->state != DS_SNMP_DATA_AVL && sp->state != DS_SNMP_DATA_ERR) {
        DS_SNMP_DBG("ds_snmp_read: no SNMP data\n");
        if (uiop->uio_fmode & (FNDELAY | FNONBLOCK)) {
            mutex_exit(&sp->lock);
            return (EAGAIN);
        }
        while (sp->state != DS_SNMP_DATA_AVL &&
            sp->state != DS_SNMP_DATA_ERR) {
            if (cv_wait_sig(&sp->state_cv, &sp->lock) == 0) {
                mutex_exit(&sp->lock);
                return (EINTR);
            }
        }
    }

    /*
     * If there has been an error, it could be because the agent
     * returned failure and there is no data to read, or an ldc-reset
     * has happened.  Figure out which and return appropriate
     * error to the caller.
     */
    if (sp->state == DS_SNMP_DATA_ERR) {
        if (sp->sc_reset == B_TRUE) {
            mutex_exit(&sp->lock);
            DS_SNMP_DBG("ds_snmp_read: sc got reset, "
                "returning ECANCELED\n");
            return (ECANCELED);
        } else {
            sp->state = DS_SNMP_READY;
            cv_broadcast(&sp->state_cv);
            mutex_exit(&sp->lock);
            DS_SNMP_DBG("ds_snmp_read: data error, "
                "returning EIO\n");
            return (EIO);
        }
    }

    if (len > sp->data_len)
        len = sp->data_len;

    tmpbufp = kmem_alloc(len, KM_SLEEP);

    bcopy(sp->data, (void *)tmpbufp, len);
    kmem_free(sp->data, sp->data_len);
    sp->data = (caddr_t)NULL;
    sp->data_len = 0;

    /*
     * SNMP data has been consumed, wake up anyone waiting to send
     */
    sp->state = DS_SNMP_READY;
    cv_broadcast(&sp->state_cv);

    mutex_exit(&sp->lock);

    retval = uiomove(tmpbufp, len, UIO_READ, uiop);
    kmem_free(tmpbufp, len);

    return (retval);
}

/*ARGSUSED*/
static int
ds_snmp_write(dev_t dev, struct uio *uiop, cred_t *credp)
{
    ds_snmp_state_t *sp;
    ds_snmp_msg_t hdr;
    minor_t minor;
    size_t len;
    caddr_t tmpbufp;

    /*
     * Check if there was an sc reset; if yes, wait until we have the
     * service back again.
     */
    mutex_enter(&ds_snmp_lock);
    while (ds_snmp_has_service == B_FALSE) {
        DS_SNMP_DBG("ds_snmp_write: waiting for service\n");
        if (cv_wait_sig(&ds_snmp_service_cv, &ds_snmp_lock) == 0) {
            mutex_exit(&ds_snmp_lock);
            return (EINTR);
        }
    }
    mutex_exit(&ds_snmp_lock);

    minor = getminor(dev);
    if ((sp = ddi_get_soft_state(ds_snmp_statep, minor)) == NULL)
        return (ENXIO);

    len = uiop->uio_resid + sizeof (ds_snmp_msg_t);
    tmpbufp = kmem_alloc(len, KM_SLEEP);

    if (uiomove(tmpbufp + sizeof (ds_snmp_msg_t),
        len - sizeof (ds_snmp_msg_t), UIO_WRITE, uiop) != 0) {
        kmem_free(tmpbufp, len);
        return (EIO);
    }

    mutex_enter(&sp->lock);

    if (sp->sc_reset == B_TRUE) {
        mutex_exit(&sp->lock);
        kmem_free(tmpbufp, len);
        DS_SNMP_DBG("ds_snmp_write: sc_reset is TRUE, "
            "returning ECANCELD\n");
        return (ECANCELED);
    }

    /*
     * wait if earlier transaction is not yet completed
     */
    while (sp->state != DS_SNMP_READY) {
        if (cv_wait_sig(&sp->state_cv, &sp->lock) == 0) {
            mutex_exit(&sp->lock);
            kmem_free(tmpbufp, len);
            return (EINTR);
        }
        /*
         * Normally, only a reader would ever wake us up. But if we
         * did get signalled with an ERROR, it could only mean there
         * was an sc reset and there's no point waiting; we need to
         * fail this write().
         */
        if (sp->state == DS_SNMP_DATA_ERR && sp->sc_reset == B_TRUE) {
            DS_SNMP_DBG("ds_snmp_write: woke up with an sc_reset, "
                "returning ECANCELED\n");
            mutex_exit(&sp->lock);
            kmem_free(tmpbufp, len);
            return (ECANCELED);
        }
    }

    if (sp->req_id == (((uint64_t)1 << DS_SNMP_MINOR_SHIFT) - 1))
        sp->req_id = 0; /* Reset */

    hdr.seq_num = ((uint64_t)minor << DS_SNMP_MINOR_SHIFT) | sp->req_id;
    sp->last_req_id = hdr.seq_num;
    (sp->req_id)++;

    /*
     * Set state to SNMP_REQUESTED, but don't wakeup anyone yet
     */
    sp->state = DS_SNMP_REQUESTED;

    mutex_exit(&sp->lock);

    hdr.type = DS_SNMP_REQUEST;
    bcopy((void *)&hdr, (void *)tmpbufp, sizeof (hdr));

    /*
     * If the service went away since the time we entered this
     * routine and now, tough luck. Just ignore the current
     * write() and return.
     */
    mutex_enter(&ds_snmp_lock);
    if (ds_snmp_has_service == B_FALSE) {
        DS_SNMP_DBG("ds_snmp_write: service went away, aborting "
            "write, returning ECANCELED\n");
        mutex_exit(&ds_snmp_lock);
        kmem_free(tmpbufp, len);
        return (ECANCELED);
    }
    DS_SNMP_DBG("ds_snmp_write: ds_cap_send(0x%lx, %lu) called.\n",
        ds_snmp_handle, len);
    (void) ds_cap_send(ds_snmp_handle, tmpbufp, len);
    mutex_exit(&ds_snmp_lock);

    kmem_free(tmpbufp, len);

    return (0);
}

/*ARGSUSED*/
static int
ds_snmp_ioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp,
    int *rvalp)
{
    ds_snmp_state_t *sp;
    struct dssnmp_info info;
    minor_t minor;

    /*
     * Check if there was an sc reset; if yes, wait until we have the
     * service back again.
     */
    mutex_enter(&ds_snmp_lock);
    while (ds_snmp_has_service == B_FALSE) {
        DS_SNMP_DBG("ds_snmp_ioctl: waiting for service\n");
        if (cv_wait_sig(&ds_snmp_service_cv, &ds_snmp_lock) == 0) {
            mutex_exit(&ds_snmp_lock);
            return (EINTR);
        }
    }
    mutex_exit(&ds_snmp_lock);

    DS_SNMP_DBG("ds_snmp_ioctl: hdl=0x%lx\n", ds_snmp_handle);

    minor = getminor(dev);
    if ((sp = ddi_get_soft_state(ds_snmp_statep, minor)) == NULL)
        return (ENXIO);

    if (!(mode & FREAD))
        return (EACCES);

    switch (cmd) {
    case DSSNMP_GETINFO:
        mutex_enter(&sp->lock);

        if (sp->sc_reset == B_TRUE) {
            mutex_exit(&sp->lock);
            DS_SNMP_DBG("ds_snmp_ioctl: returning ECANCELED\n");
            return (ECANCELED);
        }

        while (sp->state != DS_SNMP_DATA_AVL &&
            sp->state != DS_SNMP_DATA_ERR) {
            DS_SNMP_DBG("ds_snmp_ioctl: state=%d, sc_reset=%d, "
                "waiting for data\n", sp->state, sp->sc_reset);
            if (cv_wait_sig(&sp->state_cv, &sp->lock) == 0) {
                sp->state = DS_SNMP_READY;
                mutex_exit(&sp->lock);
                return (EINTR);
            }
        }
        DS_SNMP_DBG("ds_snmp_ioctl: state=%d, sc_reset=%d, "
            "out of wait!\n", sp->state, sp->sc_reset);

        /*
         * If there has been an error, it could be because the
         * agent returned failure and there is no data to read,
         * or an ldc-reset has happened.  Figure out which and
         * return appropriate error to the caller.
         */
        if (sp->state == DS_SNMP_DATA_ERR) {
            if (sp->sc_reset == B_TRUE) {
                mutex_exit(&sp->lock);
                DS_SNMP_DBG("ds_snmp_ioctl: sc_reset=TRUE "
                    "returning ECANCELED\n");
                return (ECANCELED);
            } else {
                sp->state = DS_SNMP_READY;
                cv_broadcast(&sp->state_cv);
                mutex_exit(&sp->lock);
                DS_SNMP_DBG("ds_snmp_ioctl: sc_reset=FALSE "
                    "returning EIO\n");
                return (EIO);
            }
        }

        info.size = sp->data_len;
        info.token = sp->gencount;

        mutex_exit(&sp->lock);

        if (ddi_copyout(&info, (void *)arg, sizeof (info), mode) != 0)
            return (EFAULT);
        break;

    case DSSNMP_CLRLNKRESET:
        mutex_enter(&sp->lock);

        DS_SNMP_DBG("ds_snmp_ioctl: DSSNMP_CLRLNKRESET\n");
        DS_SNMP_DBG("ds_snmp_ioctl: sc_reset=%d\n", sp->sc_reset);

        if (sp->sc_reset == B_TRUE) {
            if (sp->data) {
                DS_SNMP_DBG("ds_snmp_ioctl: data=%p, len=%lu\n",
                    sp->data, sp->data_len);
                kmem_free(sp->data, sp->data_len);
            }
            sp->data = NULL;
            sp->data_len = 0;
            sp->state = DS_SNMP_READY;
            sp->req_id = 0;
            sp->last_req_id = 0;
            sp->sc_reset = B_FALSE;
        }
        mutex_exit(&sp->lock);
        break;

    default:
        return (ENOTTY);
    }

    return (0);
}

/*
 * DS Callbacks
 */
/*ARGSUSED*/
static void
ds_snmp_reg_handler(ds_cb_arg_t arg, ds_ver_t *ver, ds_svc_hdl_t hdl)
{
    DS_SNMP_DBG("ds_snmp_reg_handler: registering handle 0x%lx for version "
        "0x%x:0x%x\n", (uint64_t)hdl, ver->major, ver->minor);

    mutex_enter(&ds_snmp_lock);

    ASSERT(ds_snmp_handle == DS_INVALID_HDL);

    ds_snmp_handle = hdl;
    ds_snmp_has_service = B_TRUE;

    cv_broadcast(&ds_snmp_service_cv);

    mutex_exit(&ds_snmp_lock);

}

/*ARGSUSED*/
static void
ds_snmp_unreg_handler(ds_cb_arg_t arg)
{
    minor_t minor;
    ds_snmp_state_t *sp;

    DS_SNMP_DBG("ds_snmp_unreg_handler: un-registering ds_snmp service\n");

    mutex_enter(&ds_snmp_lock);

    if (ds_snmp_num_opens) {
        DS_SNMP_DBG("ds_snmp_unreg_handler: %d opens, sc reset!\n",
            ds_snmp_num_opens);
        for (minor = 1; minor <= DS_SNMP_MAX_OPENS; minor++) {
            if (ds_snmp_is_open(minor)) {
                DS_SNMP_DBG("ds_snmp_unreg_handler: minor %d "
                    "open\n", minor);
                sp = ddi_get_soft_state(ds_snmp_statep, minor);
                if (sp == NULL)
                    continue;

                /*
                 * Set the sc_reset flag and break any waiters
                 * out of their existing reads/writes/ioctls.
                 */
                DS_SNMP_DBG("ds_snmp_unreg_hdlr: about to "
                    "signal waiters\n");
                mutex_enter(&sp->lock);
                sp->sc_reset = B_TRUE;
                sp->state = DS_SNMP_DATA_ERR;
                cv_broadcast(&sp->state_cv);
                mutex_exit(&sp->lock);
            }
        }
    }

    ds_snmp_handle = DS_INVALID_HDL;
    ds_snmp_has_service = B_FALSE;

    DS_SNMP_DBG("ds_snmp_unreg_handler: handle invalidated\n");

    mutex_exit(&ds_snmp_lock);
}

/*ARGSUSED*/
static void
ds_snmp_data_handler(ds_cb_arg_t arg, void *buf, size_t buflen)
{
    ds_snmp_state_t *sp;
    ds_snmp_msg_t   hdr;
    size_t      snmp_size;
    minor_t     minor;

    /*
     * Make sure the header is at least valid
     */
    if (buflen < sizeof (hdr)) {
        cmn_err(CE_WARN,
        "ds_snmp_data_handler: buflen <%lu> too small", buflen);
        return;
    }

    ASSERT(buf != NULL);
    bcopy(buf, (void *)&hdr, sizeof (hdr));

    DS_SNMP_DBG("ds_snmp_data_handler: msg buf len 0x%lx : type 0x%lx, "
        "seqn 0x%lx\n", buflen, hdr.type, hdr.seq_num);

    minor = (int)(hdr.seq_num >> DS_SNMP_MINOR_SHIFT);
    if ((sp = ddi_get_soft_state(ds_snmp_statep, minor)) == NULL)
        return;

    mutex_enter(&sp->lock);

    /*
     * If there is no pending SNMP request, then we've received
     * bogus data or an SNMP trap or the reader was interrupted.
     * Since we don't yet support SNMP traps, ignore it.
     */
    if (sp->state != DS_SNMP_REQUESTED) {
        DS_SNMP_DBG("Received SNMP data without request");
        mutex_exit(&sp->lock);
        return;
    }

    /*
     * Response to a request therefore old SNMP must've been consumed
     */
    ASSERT(sp->data_len == 0);
    ASSERT(sp->data == NULL);

    /*
     * Response seq_num should match our request seq_num
     */
    if (hdr.seq_num != sp->last_req_id) {
        cmn_err(CE_WARN, "Received DS snmp data out of sequence with "
            "request");
        mutex_exit(&sp->lock);
        return;
    }

    if (hdr.type == DS_SNMP_ERROR) {
        sp->state = DS_SNMP_DATA_ERR;
        DS_SNMP_DBG("ds_snmp_data_handler: hdr.type = DS_SNMP_ERROR\n");
    } else {
        snmp_size = buflen - sizeof (ds_snmp_msg_t);
        sp->data = kmem_alloc(snmp_size, KM_SLEEP);
        sp->data_len = snmp_size;
        sp->state = DS_SNMP_DATA_AVL;

        bcopy((caddr_t)buf + sizeof (ds_snmp_msg_t),
            sp->data, sp->data_len);
    }

    sp->gencount++;

    /*
     * Wake up any readers waiting for data
     */
    cv_broadcast(&sp->state_cv);
    mutex_exit(&sp->lock);
}