// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * rio_cm - RapidIO Channelized Messaging Driver
 *
 * Copyright 2013-2016 Integrated Device Technology, Inc.
 * Copyright (c) 2015, Prodrive Technologies
 * Copyright (c) 2015, RapidIO Trade Association
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/rio.h>
#include <linux/rio_drv.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/interrupt.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/reboot.h>
#include <linux/bitops.h>
#include <linux/printk.h>
#include <linux/rio_cm_cdev.h>

#define DRV_NAME        "rio_cm"
#define DRV_VERSION     "1.0.0"
#define DRV_AUTHOR      "Alexandre Bounine <alexandre.bounine@idt.com>"
#define DRV_DESC        "RapidIO Channelized Messaging Driver"
#define DEV_NAME        "rio_cm"

/* Debug output filtering masks */
enum {
        DBG_NONE        = 0,
        DBG_INIT        = BIT(0), /* driver init */
        DBG_EXIT        = BIT(1), /* driver exit */
        DBG_MPORT       = BIT(2), /* mport add/remove */
        DBG_RDEV        = BIT(3), /* RapidIO device add/remove */
        DBG_CHOP        = BIT(4), /* channel operations */
        DBG_WAIT        = BIT(5), /* waiting for events */
        DBG_TX          = BIT(6), /* message TX */
        DBG_TX_EVENT    = BIT(7), /* message TX event */
        DBG_RX_DATA     = BIT(8), /* inbound data messages */
        DBG_RX_CMD      = BIT(9), /* inbound REQ/ACK/NACK messages */
        DBG_ALL         = ~0,
};

#ifdef DEBUG
#define riocm_debug(level, fmt, arg...) \
        do { \
                if (DBG_##level & dbg_level) \
                        pr_debug(DRV_NAME ": %s " fmt "\n", \
                                __func__, ##arg); \
        } while (0)
#else
#define riocm_debug(level, fmt, arg...) \
                no_printk(KERN_DEBUG pr_fmt(DRV_NAME fmt "\n"), ##arg)
#endif

#define riocm_warn(fmt, arg...) \
        pr_warn(DRV_NAME ": %s WARNING " fmt "\n", __func__, ##arg)

#define riocm_error(fmt, arg...) \
        pr_err(DRV_NAME ": %s ERROR " fmt "\n", __func__, ##arg)


static int cmbox = 1;
module_param(cmbox, int, S_IRUGO);
MODULE_PARM_DESC(cmbox, "RapidIO Mailbox number (default 1)");

static int chstart = 256;
module_param(chstart, int, S_IRUGO);
MODULE_PARM_DESC(chstart,
                 "Start channel number for dynamic allocation (default 256)");

#ifdef DEBUG
static u32 dbg_level = DBG_NONE;
module_param(dbg_level, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(dbg_level, "Debugging output level (default 0 = none)");
#endif

MODULE_AUTHOR(DRV_AUTHOR);
MODULE_DESCRIPTION(DRV_DESC);
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);

#define RIOCM_TX_RING_SIZE      128
#define RIOCM_RX_RING_SIZE      128
#define RIOCM_CONNECT_TO        3 /* connect response TO (in sec) */

#define RIOCM_MAX_CHNUM         0xffff /* Use full range of u16 field */
#define RIOCM_CHNUM_AUTO        0
#define RIOCM_MAX_EP_COUNT      0x10000 /* Max number of endpoints */

enum rio_cm_state {
        RIO_CM_IDLE,
        RIO_CM_CONNECT,
        RIO_CM_CONNECTED,
        RIO_CM_DISCONNECT,
        RIO_CM_CHAN_BOUND,
        RIO_CM_LISTEN,
        RIO_CM_DESTROYING,
};

enum rio_cm_pkt_type {
        RIO_CM_SYS      = 0xaa,
        RIO_CM_CHAN     = 0x55,
};

enum rio_cm_chop {
        CM_CONN_REQ,
        CM_CONN_ACK,
        CM_CONN_CLOSE,
        CM_DATA_MSG,
};

struct rio_ch_base_bhdr {
        u32 src_id;
        u32 dst_id;
#define RIO_HDR_LETTER_MASK 0xffff0000
#define RIO_HDR_MBOX_MASK   0x0000ffff
        u8  src_mbox;
        u8  dst_mbox;
        u8  type;
} __attribute__((__packed__));

struct rio_ch_chan_hdr {
        struct rio_ch_base_bhdr bhdr;
        u8 ch_op;
        u16 dst_ch;
        u16 src_ch;
        u16 msg_len;
        u16 rsrvd;
} __attribute__((__packed__));

struct tx_req {
        struct list_head node;
        struct rio_dev   *rdev;
        void             *buffer;
        size_t           len;
};

struct cm_dev {
        struct list_head        list;
        struct rio_mport        *mport;
        void                    *rx_buf[RIOCM_RX_RING_SIZE];
        int                     rx_slots;
        struct mutex            rx_lock;

        void                    *tx_buf[RIOCM_TX_RING_SIZE];
        int                     tx_slot;
        int                     tx_cnt;
        int                     tx_ack_slot;
        struct list_head        tx_reqs;
        spinlock_t              tx_lock;

        struct list_head        peers;
        u32                     npeers;
        struct workqueue_struct *rx_wq;
        struct work_struct      rx_work;
};

struct chan_rx_ring {
        void    *buf[RIOCM_RX_RING_SIZE];
        int     head;
        int     tail;
        int     count;

        /* Tracking RX buffers reported to upper level */
        void    *inuse[RIOCM_RX_RING_SIZE];
        int     inuse_cnt;
};

struct rio_channel {
        u16                     id;     /* local channel ID */
        struct kref             ref;    /* channel refcount */
        struct file             *filp;
        struct cm_dev           *cmdev; /* associated CM device object */
        struct rio_dev          *rdev;  /* remote RapidIO device */
        enum rio_cm_state       state;
        int                     error;
        spinlock_t              lock;
        void                    *context;
        u32                     loc_destid;     /* local destID */
        u32                     rem_destid;     /* remote destID */
        u16                     rem_channel;    /* remote channel ID */
        struct list_head        accept_queue;
        struct list_head        ch_node;
        struct completion       comp;
        struct completion       comp_close;
        struct chan_rx_ring     rx_ring;
};

struct cm_peer {
        struct list_head node;
        struct rio_dev *rdev;
};

struct rio_cm_work {
        struct work_struct work;
        struct cm_dev *cm;
        void *data;
};

struct conn_req {
        struct list_head node;
        u32 destid;     /* requester destID */
        u16 chan;       /* requester channel ID */
        struct cm_dev *cmdev;
};

/*
 * A channel_dev structure represents a CM_CDEV
 * @cdev        Character device
 * @dev         Associated device object
 */
struct channel_dev {
        struct cdev     cdev;
        struct device   *dev;
};

static struct rio_channel *riocm_ch_alloc(u16 ch_num);
static void riocm_ch_free(struct kref *ref);
static int riocm_post_send(struct cm_dev *cm, struct rio_dev *rdev,
                           void *buffer, size_t len);
static int riocm_ch_close(struct rio_channel *ch);

static DEFINE_SPINLOCK(idr_lock);
static DEFINE_IDR(ch_idr);

static LIST_HEAD(cm_dev_list);
static DECLARE_RWSEM(rdev_sem);

static struct class *dev_class;
static unsigned int dev_major;
static unsigned int dev_minor_base;
static dev_t dev_number;
static struct channel_dev riocm_cdev;

#define is_msg_capable(src_ops, dst_ops)                        \
                        ((src_ops & RIO_SRC_OPS_DATA_MSG) &&    \
                         (dst_ops & RIO_DST_OPS_DATA_MSG))
#define dev_cm_capable(dev) \
        is_msg_capable(dev->src_ops, dev->dst_ops)

static int riocm_cmp(struct rio_channel *ch, enum rio_cm_state cmp)
{
        int ret;

        spin_lock_bh(&ch->lock);
        ret = (ch->state == cmp);
        spin_unlock_bh(&ch->lock);
        return ret;
}

static int riocm_cmp_exch(struct rio_channel *ch,
                           enum rio_cm_state cmp, enum rio_cm_state exch)
{
        int ret;

        spin_lock_bh(&ch->lock);
        ret = (ch->state == cmp);
        if (ret)
                ch->state = exch;
        spin_unlock_bh(&ch->lock);
        return ret;
}

static enum rio_cm_state riocm_exch(struct rio_channel *ch,
                                    enum rio_cm_state exch)
{
        enum rio_cm_state old;

        spin_lock_bh(&ch->lock);
        old = ch->state;
        ch->state = exch;
        spin_unlock_bh(&ch->lock);
        return old;
}

static struct rio_channel *riocm_get_channel(u16 nr)
{
        struct rio_channel *ch;

        spin_lock_bh(&idr_lock);
        ch = idr_find(&ch_idr, nr);
        if (ch)
                kref_get(&ch->ref);
        spin_unlock_bh(&idr_lock);
        return ch;
}

static void riocm_put_channel(struct rio_channel *ch)
{
        kref_put(&ch->ref, riocm_ch_free);
}

static void *riocm_rx_get_msg(struct cm_dev *cm)
{
        void *msg;
        int i;

        msg = rio_get_inb_message(cm->mport, cmbox);
        if (msg) {
                for (i = 0; i < RIOCM_RX_RING_SIZE; i++) {
                        if (cm->rx_buf[i] == msg) {
                                cm->rx_buf[i] = NULL;
                                cm->rx_slots++;
                                break;
                        }
                }

                if (i == RIOCM_RX_RING_SIZE)
                        riocm_warn("no record for buffer 0x%p", msg);
        }

        return msg;
}

/*
 * riocm_rx_fill - fills a ring of receive buffers for given cm device
 * @cm: cm_dev object
 * @nent: max number of entries to fill
 *
 * Returns: none
 */
static void riocm_rx_fill(struct cm_dev *cm, int nent)
{
        int i;

        if (cm->rx_slots == 0)
                return;

        for (i = 0; i < RIOCM_RX_RING_SIZE && cm->rx_slots && nent; i++) {
                if (cm->rx_buf[i] == NULL) {
                        cm->rx_buf[i] = kmalloc(RIO_MAX_MSG_SIZE, GFP_KERNEL);
                        if (cm->rx_buf[i] == NULL)
                                break;
                        rio_add_inb_buffer(cm->mport, cmbox, cm->rx_buf[i]);
                        cm->rx_slots--;
                        nent--;
                }
        }
}

/*
 * riocm_rx_free - frees all receive buffers associated with given cm device
 * @cm: cm_dev object
 *
 * Returns: none
 */
static void riocm_rx_free(struct cm_dev *cm)
{
        int i;

        for (i = 0; i < RIOCM_RX_RING_SIZE; i++) {
                if (cm->rx_buf[i] != NULL) {
                        kfree(cm->rx_buf[i]);
                        cm->rx_buf[i] = NULL;
                }
        }
}

/*
 * riocm_req_handler - connection request handler
 * @cm: cm_dev object
 * @req_data: pointer to the request packet
 *
 * Returns: 0 if success, or
 *          -EINVAL if channel is not in correct state,
 *          -ENODEV if cannot find a channel with specified ID,
 *          -ENOMEM if unable to allocate memory to store the request
 */
static int riocm_req_handler(struct cm_dev *cm, void *req_data)
{
        struct rio_channel *ch;
        struct conn_req *req;
        struct rio_ch_chan_hdr *hh = req_data;
        u16 chnum;

        chnum = ntohs(hh->dst_ch);

        ch = riocm_get_channel(chnum);

        if (!ch)
                return -ENODEV;

        if (ch->state != RIO_CM_LISTEN) {
                riocm_debug(RX_CMD, "channel %d is not in listen state", chnum);
                riocm_put_channel(ch);
                return -EINVAL;
        }

        req = kzalloc(sizeof(*req), GFP_KERNEL);
        if (!req) {
                riocm_put_channel(ch);
                return -ENOMEM;
        }

        req->destid = ntohl(hh->bhdr.src_id);
        req->chan = ntohs(hh->src_ch);
        req->cmdev = cm;

        spin_lock_bh(&ch->lock);
        list_add_tail(&req->node, &ch->accept_queue);
        spin_unlock_bh(&ch->lock);
        complete(&ch->comp);
        riocm_put_channel(ch);

        return 0;
}

/*
 * riocm_resp_handler - response to connection request handler
 * @resp_data: pointer to the response packet
 *
 * Returns: 0 if success, or
 *          -EINVAL if channel is not in correct state,
 *          -ENODEV if cannot find a channel with specified ID,
 */
static int riocm_resp_handler(void *resp_data)
{
        struct rio_channel *ch;
        struct rio_ch_chan_hdr *hh = resp_data;
        u16 chnum;

        chnum = ntohs(hh->dst_ch);
        ch = riocm_get_channel(chnum);
        if (!ch)
                return -ENODEV;

        if (ch->state != RIO_CM_CONNECT) {
                riocm_put_channel(ch);
                return -EINVAL;
        }

        riocm_exch(ch, RIO_CM_CONNECTED);
        ch->rem_channel = ntohs(hh->src_ch);
        complete(&ch->comp);
        riocm_put_channel(ch);

        return 0;
}

/*
 * riocm_close_handler - channel close request handler
 * @req_data: pointer to the request packet
 *
 * Returns: 0 if success, or
 *          -ENODEV if cannot find a channel with specified ID,
 *            + error codes returned by riocm_ch_close.
 */
static int riocm_close_handler(void *data)
{
        struct rio_channel *ch;
        struct rio_ch_chan_hdr *hh = data;
        int ret;

        riocm_debug(RX_CMD, "for ch=%d", ntohs(hh->dst_ch));

        spin_lock_bh(&idr_lock);
        ch = idr_find(&ch_idr, ntohs(hh->dst_ch));
        if (!ch) {
                spin_unlock_bh(&idr_lock);
                return -ENODEV;
        }
        idr_remove(&ch_idr, ch->id);
        spin_unlock_bh(&idr_lock);

        riocm_exch(ch, RIO_CM_DISCONNECT);

        ret = riocm_ch_close(ch);
        if (ret)
                riocm_debug(RX_CMD, "riocm_ch_close() returned %d", ret);

        return 0;
}

/*
 * rio_cm_handler - function that services request (non-data) packets
 * @cm: cm_dev object
 * @data: pointer to the packet
 */
static void rio_cm_handler(struct cm_dev *cm, void *data)
{
        struct rio_ch_chan_hdr *hdr;

        if (!rio_mport_is_running(cm->mport))
                goto out;

        hdr = data;

        riocm_debug(RX_CMD, "OP=%x for ch=%d from %d",
                    hdr->ch_op, ntohs(hdr->dst_ch), ntohs(hdr->src_ch));

        switch (hdr->ch_op) {
        case CM_CONN_REQ:
                riocm_req_handler(cm, data);
                break;
        case CM_CONN_ACK:
                riocm_resp_handler(data);
                break;
        case CM_CONN_CLOSE:
                riocm_close_handler(data);
                break;
        default:
                riocm_error("Invalid packet header");
                break;
        }
out:
        kfree(data);
}

/*
 * rio_rx_data_handler - received data packet handler
 * @cm: cm_dev object
 * @buf: data packet
 *
 * Returns: 0 if success, or
 *          -ENODEV if cannot find a channel with specified ID,
 *          -EIO if channel is not in CONNECTED state,
 *          -ENOMEM if channel RX queue is full (packet discarded)
 */
static int rio_rx_data_handler(struct cm_dev *cm, void *buf)
{
        struct rio_ch_chan_hdr *hdr;
        struct rio_channel *ch;

        hdr = buf;

        riocm_debug(RX_DATA, "for ch=%d", ntohs(hdr->dst_ch));

        ch = riocm_get_channel(ntohs(hdr->dst_ch));
        if (!ch) {
                /* Discard data message for non-existing channel */
                kfree(buf);
                return -ENODEV;
        }

        /* Place pointer to the buffer into channel's RX queue */
        spin_lock(&ch->lock);

        if (ch->state != RIO_CM_CONNECTED) {
                /* Channel is not ready to receive data, discard a packet */
                riocm_debug(RX_DATA, "ch=%d is in wrong state=%d",
                            ch->id, ch->state);
                spin_unlock(&ch->lock);
                kfree(buf);
                riocm_put_channel(ch);
                return -EIO;
        }

        if (ch->rx_ring.count == RIOCM_RX_RING_SIZE) {
                /* If RX ring is full, discard a packet */
                riocm_debug(RX_DATA, "ch=%d is full", ch->id);
                spin_unlock(&ch->lock);
                kfree(buf);
                riocm_put_channel(ch);
                return -ENOMEM;
        }

        ch->rx_ring.buf[ch->rx_ring.head] = buf;
        ch->rx_ring.head++;
        ch->rx_ring.count++;
        ch->rx_ring.head %= RIOCM_RX_RING_SIZE;

        complete(&ch->comp);

        spin_unlock(&ch->lock);
        riocm_put_channel(ch);

        return 0;
}

/*
 * rio_ibmsg_handler - inbound message packet handler
 */
static void rio_ibmsg_handler(struct work_struct *work)
{
        struct cm_dev *cm = container_of(work, struct cm_dev, rx_work);
        void *data;
        struct rio_ch_chan_hdr *hdr;

        if (!rio_mport_is_running(cm->mport))
                return;

        while (1) {
                mutex_lock(&cm->rx_lock);
                data = riocm_rx_get_msg(cm);
                if (data)
                        riocm_rx_fill(cm, 1);
                mutex_unlock(&cm->rx_lock);

                if (data == NULL)
                        break;

                hdr = data;

                if (hdr->bhdr.type != RIO_CM_CHAN) {
                        /* For now simply discard packets other than channel */
                        riocm_error("Unsupported TYPE code (0x%x). Msg dropped",
                                    hdr->bhdr.type);
                        kfree(data);
                        continue;
                }

                /* Process a channel message */
                if (hdr->ch_op == CM_DATA_MSG)
                        rio_rx_data_handler(cm, data);
                else
                        rio_cm_handler(cm, data);
        }
}

static void riocm_inb_msg_event(struct rio_mport *mport, void *dev_id,
                                int mbox, int slot)
{
        struct cm_dev *cm = dev_id;

        if (rio_mport_is_running(cm->mport) && !work_pending(&cm->rx_work))
                queue_work(cm->rx_wq, &cm->rx_work);
}

/*
 * rio_txcq_handler - TX completion handler
 * @cm: cm_dev object
 * @slot: TX queue slot
 *
 * TX completion handler also ensures that pending request packets are placed
 * into transmit queue as soon as a free slot becomes available. This is done
 * to give higher priority to request packets during high intensity data flow.
 */
static void rio_txcq_handler(struct cm_dev *cm, int slot)
{
        int ack_slot;

        /* ATTN: Add TX completion notification if/when direct buffer
         * transfer is implemented. At this moment only correct tracking
         * of tx_count is important.
         */
        riocm_debug(TX_EVENT, "for mport_%d slot %d tx_cnt %d",
                    cm->mport->id, slot, cm->tx_cnt);

        spin_lock(&cm->tx_lock);
        ack_slot = cm->tx_ack_slot;

        if (ack_slot == slot)
                riocm_debug(TX_EVENT, "slot == ack_slot");

        while (cm->tx_cnt && ((ack_slot != slot) ||
               (cm->tx_cnt == RIOCM_TX_RING_SIZE))) {

                cm->tx_buf[ack_slot] = NULL;
                ++ack_slot;
                ack_slot &= (RIOCM_TX_RING_SIZE - 1);
                cm->tx_cnt--;
        }

        if (cm->tx_cnt < 0 || cm->tx_cnt > RIOCM_TX_RING_SIZE)
                riocm_error("tx_cnt %d out of sync", cm->tx_cnt);

        WARN_ON((cm->tx_cnt < 0) || (cm->tx_cnt > RIOCM_TX_RING_SIZE));

        cm->tx_ack_slot = ack_slot;

        /*
         * If there are pending requests, insert them into transmit queue
         */
        if (!list_empty(&cm->tx_reqs) && (cm->tx_cnt < RIOCM_TX_RING_SIZE)) {
                struct tx_req *req, *_req;
                int rc;

                list_for_each_entry_safe(req, _req, &cm->tx_reqs, node) {
                        list_del(&req->node);
                        cm->tx_buf[cm->tx_slot] = req->buffer;
                        rc = rio_add_outb_message(cm->mport, req->rdev, cmbox,
                                                  req->buffer, req->len);
                        kfree(req->buffer);
                        kfree(req);

                        ++cm->tx_cnt;
                        ++cm->tx_slot;
                        cm->tx_slot &= (RIOCM_TX_RING_SIZE - 1);
                        if (cm->tx_cnt == RIOCM_TX_RING_SIZE)
                                break;
                }
        }

        spin_unlock(&cm->tx_lock);
}

static void riocm_outb_msg_event(struct rio_mport *mport, void *dev_id,
                                 int mbox, int slot)
{
        struct cm_dev *cm = dev_id;

        if (cm && rio_mport_is_running(cm->mport))
                rio_txcq_handler(cm, slot);
}

static int riocm_queue_req(struct cm_dev *cm, struct rio_dev *rdev,
                           void *buffer, size_t len)
{
        unsigned long flags;
        struct tx_req *treq;

        treq = kzalloc(sizeof(*treq), GFP_KERNEL);
        if (treq == NULL)
                return -ENOMEM;

        treq->rdev = rdev;
        treq->buffer = buffer;
        treq->len = len;

        spin_lock_irqsave(&cm->tx_lock, flags);
        list_add_tail(&treq->node, &cm->tx_reqs);
        spin_unlock_irqrestore(&cm->tx_lock, flags);
        return 0;
}

/*
 * riocm_post_send - helper function that places packet into msg TX queue
 * @cm: cm_dev object
 * @rdev: target RapidIO device object (required by outbound msg interface)
 * @buffer: pointer to a packet buffer to send
 * @len: length of data to transfer
 * @req: request priority flag
 *
 * Returns: 0 if success, or error code otherwise.
 */
static int riocm_post_send(struct cm_dev *cm, struct rio_dev *rdev,
                           void *buffer, size_t len)
{
        int rc;
        unsigned long flags;

        spin_lock_irqsave(&cm->tx_lock, flags);

        if (cm->mport == NULL) {
                rc = -ENODEV;
                goto err_out;
        }

        if (cm->tx_cnt == RIOCM_TX_RING_SIZE) {
                riocm_debug(TX, "Tx Queue is full");
                rc = -EBUSY;
                goto err_out;
        }

        cm->tx_buf[cm->tx_slot] = buffer;
        rc = rio_add_outb_message(cm->mport, rdev, cmbox, buffer, len);

        riocm_debug(TX, "Add buf@%p destid=%x tx_slot=%d tx_cnt=%d",
                 buffer, rdev->destid, cm->tx_slot, cm->tx_cnt);

        ++cm->tx_cnt;
        ++cm->tx_slot;
        cm->tx_slot &= (RIOCM_TX_RING_SIZE - 1);

err_out:
        spin_unlock_irqrestore(&cm->tx_lock, flags);
        return rc;
}

/*
 * riocm_ch_send - sends a data packet to a remote device
 * @ch_id: local channel ID
 * @buf: pointer to a data buffer to send (including CM header)
 * @len: length of data to transfer (including CM header)
 *
 * ATTN: ASSUMES THAT THE HEADER SPACE IS RESERVED PART OF THE DATA PACKET
 *
 * Returns: 0 if success, or
 *          -EINVAL if one or more input parameters is/are not valid,
 *          -ENODEV if cannot find a channel with specified ID,
 *          -EAGAIN if a channel is not in CONNECTED state,
 *          + error codes returned by HW send routine.
 */
static int riocm_ch_send(u16 ch_id, void *buf, int len)
{
        struct rio_channel *ch;
        struct rio_ch_chan_hdr *hdr;
        int ret;

        if (buf == NULL || ch_id == 0 || len == 0 || len > RIO_MAX_MSG_SIZE)
                return -EINVAL;

        ch = riocm_get_channel(ch_id);
        if (!ch) {
                riocm_error("%s(%d) ch_%d not found", current->comm,
                            task_pid_nr(current), ch_id);
                return -ENODEV;
        }

        if (!riocm_cmp(ch, RIO_CM_CONNECTED)) {
                ret = -EAGAIN;
                goto err_out;
        }

        /*
         * Fill buffer header section with corresponding channel data
         */
        hdr = buf;

        hdr->bhdr.src_id = htonl(ch->loc_destid);
        hdr->bhdr.dst_id = htonl(ch->rem_destid);
        hdr->bhdr.src_mbox = cmbox;
        hdr->bhdr.dst_mbox = cmbox;
        hdr->bhdr.type = RIO_CM_CHAN;
        hdr->ch_op = CM_DATA_MSG;
        hdr->dst_ch = htons(ch->rem_channel);
        hdr->src_ch = htons(ch->id);
        hdr->msg_len = htons((u16)len);

        /* ATTN: the function call below relies on the fact that underlying
         * HW-specific add_outb_message() routine copies TX data into its own
         * internal transfer buffer (true for all RIONET compatible mport
         * drivers). Must be reviewed if mport driver uses the buffer directly.
         */

        ret = riocm_post_send(ch->cmdev, ch->rdev, buf, len);
        if (ret)
                riocm_debug(TX, "ch %d send_err=%d", ch->id, ret);
err_out:
        riocm_put_channel(ch);
        return ret;
}

static int riocm_ch_free_rxbuf(struct rio_channel *ch, void *buf)
{
        int i, ret = -EINVAL;

        spin_lock_bh(&ch->lock);

        for (i = 0; i < RIOCM_RX_RING_SIZE; i++) {
                if (ch->rx_ring.inuse[i] == buf) {
                        ch->rx_ring.inuse[i] = NULL;
                        ch->rx_ring.inuse_cnt--;
                        ret = 0;
                        break;
                }
        }

        spin_unlock_bh(&ch->lock);

        if (!ret)
                kfree(buf);

        return ret;
}

/*
 * riocm_ch_receive - fetch a data packet received for the specified channel
 * @ch: local channel ID
 * @buf: pointer to a packet buffer
 * @timeout: timeout to wait for incoming packet (in jiffies)
 *
 * Returns: 0 and valid buffer pointer if success, or NULL pointer and one of:
 *          -EAGAIN if a channel is not in CONNECTED state,
 *          -ENOMEM if in-use tracking queue is full,
 *          -ETIME if wait timeout expired,
 *          -EINTR if wait was interrupted.
 */
static int riocm_ch_receive(struct rio_channel *ch, void **buf, long timeout)
{
        void *rxmsg = NULL;
        int i, ret = 0;
        long wret;

        if (!riocm_cmp(ch, RIO_CM_CONNECTED)) {
                ret = -EAGAIN;
                goto out;
        }

        if (ch->rx_ring.inuse_cnt == RIOCM_RX_RING_SIZE) {
                /* If we do not have entries to track buffers given to upper
                 * layer, reject request.
                 */
                ret = -ENOMEM;
                goto out;
        }

        wret = wait_for_completion_interruptible_timeout(&ch->comp, timeout);

        riocm_debug(WAIT, "wait on %d returned %ld", ch->id, wret);

        if (!wret)
                ret = -ETIME;
        else if (wret == -ERESTARTSYS)
                ret = -EINTR;
        else
                ret = riocm_cmp(ch, RIO_CM_CONNECTED) ? 0 : -ECONNRESET;

        if (ret)
                goto out;

        spin_lock_bh(&ch->lock);

        rxmsg = ch->rx_ring.buf[ch->rx_ring.tail];
        ch->rx_ring.buf[ch->rx_ring.tail] = NULL;
        ch->rx_ring.count--;
        ch->rx_ring.tail++;
        ch->rx_ring.tail %= RIOCM_RX_RING_SIZE;
        ret = -ENOMEM;

        for (i = 0; i < RIOCM_RX_RING_SIZE; i++) {
                if (ch->rx_ring.inuse[i] == NULL) {
                        ch->rx_ring.inuse[i] = rxmsg;
                        ch->rx_ring.inuse_cnt++;
                        ret = 0;
                        break;
                }
        }

        if (ret) {
                /* We have no entry to store pending message: drop it */
                kfree(rxmsg);
                rxmsg = NULL;
        }

        spin_unlock_bh(&ch->lock);
out:
        *buf = rxmsg;
        return ret;
}

/*
 * riocm_ch_connect - sends a connect request to a remote device
 * @loc_ch: local channel ID
 * @cm: CM device to send connect request
 * @peer: target RapidIO device
 * @rem_ch: remote channel ID
 *
 * Returns: 0 if success, or
 *          -EINVAL if the channel is not in IDLE state,
 *          -EAGAIN if no connection request available immediately,
 *          -ETIME if ACK response timeout expired,
 *          -EINTR if wait for response was interrupted.
 */
static int riocm_ch_connect(u16 loc_ch, struct cm_dev *cm,
                            struct cm_peer *peer, u16 rem_ch)
{
        struct rio_channel *ch = NULL;
        struct rio_ch_chan_hdr *hdr;
        int ret;
        long wret;

        ch = riocm_get_channel(loc_ch);
        if (!ch)
                return -ENODEV;

        if (!riocm_cmp_exch(ch, RIO_CM_IDLE, RIO_CM_CONNECT)) {
                ret = -EINVAL;
                goto conn_done;
        }

        ch->cmdev = cm;
        ch->rdev = peer->rdev;
        ch->context = NULL;
        ch->loc_destid = cm->mport->host_deviceid;
        ch->rem_channel = rem_ch;

        /*
         * Send connect request to the remote RapidIO device
         */

        hdr = kzalloc(sizeof(*hdr), GFP_KERNEL);
        if (hdr == NULL) {
                ret = -ENOMEM;
                goto conn_done;
        }

        hdr->bhdr.src_id = htonl(ch->loc_destid);
        hdr->bhdr.dst_id = htonl(peer->rdev->destid);
        hdr->bhdr.src_mbox = cmbox;
        hdr->bhdr.dst_mbox = cmbox;
        hdr->bhdr.type = RIO_CM_CHAN;
        hdr->ch_op = CM_CONN_REQ;
        hdr->dst_ch = htons(rem_ch);
        hdr->src_ch = htons(loc_ch);

        /* ATTN: the function call below relies on the fact that underlying
         * HW-specific add_outb_message() routine copies TX data into its
         * internal transfer buffer. Must be reviewed if mport driver uses
         * this buffer directly.
         */
        ret = riocm_post_send(cm, peer->rdev, hdr, sizeof(*hdr));

        if (ret != -EBUSY) {
                kfree(hdr);
        } else {
                ret = riocm_queue_req(cm, peer->rdev, hdr, sizeof(*hdr));
                if (ret)
                        kfree(hdr);
        }

        if (ret) {
                riocm_cmp_exch(ch, RIO_CM_CONNECT, RIO_CM_IDLE);

                goto conn_done;
        }

        /* Wait for connect response from the remote device */
        wret = wait_for_completion_interruptible_timeout(&ch->comp,
                                                         RIOCM_CONNECT_TO * HZ);
        riocm_debug(WAIT, "wait on %d returns %ld", ch->id, wret);

        if (!wret)
                ret = -ETIME;
        else if (wret == -ERESTARTSYS)
                ret = -EINTR;
        else
                ret = riocm_cmp(ch, RIO_CM_CONNECTED) ? 0 : -1;

conn_done:
        riocm_put_channel(ch);
        return ret;
}

static int riocm_send_ack(struct rio_channel *ch)
{
        struct rio_ch_chan_hdr *hdr;
        int ret;

        hdr = kzalloc(sizeof(*hdr), GFP_KERNEL);
        if (hdr == NULL)
                return -ENOMEM;

        hdr->bhdr.src_id = htonl(ch->loc_destid);
        hdr->bhdr.dst_id = htonl(ch->rem_destid);
        hdr->dst_ch = htons(ch->rem_channel);
        hdr->src_ch = htons(ch->id);
        hdr->bhdr.src_mbox = cmbox;
        hdr->bhdr.dst_mbox = cmbox;
        hdr->bhdr.type = RIO_CM_CHAN;
        hdr->ch_op = CM_CONN_ACK;

        /* ATTN: the function call below relies on the fact that underlying
         * add_outb_message() routine copies TX data into its internal transfer
         * buffer. Review if switching to direct buffer version.
         */
        ret = riocm_post_send(ch->cmdev, ch->rdev, hdr, sizeof(*hdr));

        if (ret == -EBUSY && !riocm_queue_req(ch->cmdev,
                                              ch->rdev, hdr, sizeof(*hdr)))
                return 0;
        kfree(hdr);

        if (ret)
                riocm_error("send ACK to ch_%d on %s failed (ret=%d)",
                            ch->id, rio_name(ch->rdev), ret);
        return ret;
}

/*
 * riocm_ch_accept - accept incoming connection request
 * @ch_id: channel ID
 * @new_ch_id: local mport device
 * @timeout: wait timeout (if 0 non-blocking call, do not wait if connection
 *           request is not available).
 *
 * Returns: pointer to new channel struct if success, or error-valued pointer:
 *          -ENODEV - cannot find specified channel or mport,
 *          -EINVAL - the channel is not in IDLE state,
 *          -EAGAIN - no connection request available immediately (timeout=0),
 *          -ENOMEM - unable to allocate new channel,
 *          -ETIME - wait timeout expired,
 *          -EINTR - wait was interrupted.
 */
static struct rio_channel *riocm_ch_accept(u16 ch_id, u16 *new_ch_id,
                                           long timeout)
{
        struct rio_channel *ch;
        struct rio_channel *new_ch;
        struct conn_req *req;
        struct cm_peer *peer;
        int found = 0;
        int err = 0;
        long wret;

        ch = riocm_get_channel(ch_id);
        if (!ch)
                return ERR_PTR(-EINVAL);

        if (!riocm_cmp(ch, RIO_CM_LISTEN)) {
                err = -EINVAL;
                goto err_put;
        }

        /* Don't sleep if this is a non blocking call */
        if (!timeout) {
                if (!try_wait_for_completion(&ch->comp)) {
                        err = -EAGAIN;
                        goto err_put;
                }
        } else {
                riocm_debug(WAIT, "on %d", ch->id);

                wret = wait_for_completion_interruptible_timeout(&ch->comp,
                                                                 timeout);
                if (!wret) {
                        err = -ETIME;
                        goto err_put;
                } else if (wret == -ERESTARTSYS) {
                        err = -EINTR;
                        goto err_put;
                }
        }

        spin_lock_bh(&ch->lock);

        if (ch->state != RIO_CM_LISTEN) {
                err = -ECANCELED;
        } else if (list_empty(&ch->accept_queue)) {
                riocm_debug(WAIT, "on %d accept_queue is empty on completion",
                            ch->id);
                err = -EIO;
        }

        spin_unlock_bh(&ch->lock);

        if (err) {
                riocm_debug(WAIT, "on %d returns %d", ch->id, err);
                goto err_put;
        }

        /* Create new channel for this connection */
        new_ch = riocm_ch_alloc(RIOCM_CHNUM_AUTO);

        if (IS_ERR(new_ch)) {
                riocm_error("failed to get channel for new req (%ld)",
                        PTR_ERR(new_ch));
                err = -ENOMEM;
                goto err_put;
        }

        spin_lock_bh(&ch->lock);

        req = list_first_entry(&ch->accept_queue, struct conn_req, node);
        list_del(&req->node);
        new_ch->cmdev = ch->cmdev;
        new_ch->loc_destid = ch->loc_destid;
        new_ch->rem_destid = req->destid;
        new_ch->rem_channel = req->chan;

        spin_unlock_bh(&ch->lock);
        riocm_put_channel(ch);
        ch = NULL;
        kfree(req);

        down_read(&rdev_sem);
        /* Find requester's device object */
        list_for_each_entry(peer, &new_ch->cmdev->peers, node) {
                if (peer->rdev->destid == new_ch->rem_destid) {
                        riocm_debug(RX_CMD, "found matching device(%s)",
                                    rio_name(peer->rdev));
                        found = 1;
                        break;
                }
        }
        up_read(&rdev_sem);

        if (!found) {
                /* If peer device object not found, simply ignore the request */
                err = -ENODEV;
                goto err_put_new_ch;
        }

        new_ch->rdev = peer->rdev;
        new_ch->state = RIO_CM_CONNECTED;
        spin_lock_init(&new_ch->lock);

        /* Acknowledge the connection request. */
        riocm_send_ack(new_ch);

        *new_ch_id = new_ch->id;
        return new_ch;

err_put_new_ch:
        spin_lock_bh(&idr_lock);
        idr_remove(&ch_idr, new_ch->id);
        spin_unlock_bh(&idr_lock);
        riocm_put_channel(new_ch);

err_put:
        if (ch)
                riocm_put_channel(ch);
        *new_ch_id = 0;
        return ERR_PTR(err);
}

/*
 * riocm_ch_listen - puts a channel into LISTEN state
 * @ch_id: channel ID
 *
 * Returns: 0 if success, or
 *          -EINVAL if the specified channel does not exists or
 *                  is not in CHAN_BOUND state.
 */
static int riocm_ch_listen(u16 ch_id)
{
        struct rio_channel *ch = NULL;
        int ret = 0;

        riocm_debug(CHOP, "(ch_%d)", ch_id);

        ch = riocm_get_channel(ch_id);
        if (!ch)
                return -EINVAL;
        if (!riocm_cmp_exch(ch, RIO_CM_CHAN_BOUND, RIO_CM_LISTEN))
                ret = -EINVAL;
        riocm_put_channel(ch);
        return ret;
}

/*
 * riocm_ch_bind - associate a channel object and an mport device
 * @ch_id: channel ID
 * @mport_id: local mport device ID
 * @context: pointer to the additional caller's context
 *
 * Returns: 0 if success, or
 *          -ENODEV if cannot find specified mport,
 *          -EINVAL if the specified channel does not exist or
 *                  is not in IDLE state.
 */
static int riocm_ch_bind(u16 ch_id, u8 mport_id, void *context)
{
        struct rio_channel *ch = NULL;
        struct cm_dev *cm;
        int rc = -ENODEV;

        riocm_debug(CHOP, "ch_%d to mport_%d", ch_id, mport_id);

        /* Find matching cm_dev object */
        down_read(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if ((cm->mport->id == mport_id) &&
                     rio_mport_is_running(cm->mport)) {
                        rc = 0;
                        break;
                }
        }

        if (rc)
                goto exit;

        ch = riocm_get_channel(ch_id);
        if (!ch) {
                rc = -EINVAL;
                goto exit;
        }

        spin_lock_bh(&ch->lock);
        if (ch->state != RIO_CM_IDLE) {
                spin_unlock_bh(&ch->lock);
                rc = -EINVAL;
                goto err_put;
        }

        ch->cmdev = cm;
        ch->loc_destid = cm->mport->host_deviceid;
        ch->context = context;
        ch->state = RIO_CM_CHAN_BOUND;
        spin_unlock_bh(&ch->lock);
err_put:
        riocm_put_channel(ch);
exit:
        up_read(&rdev_sem);
        return rc;
}

/*
 * riocm_ch_alloc - channel object allocation helper routine
 * @ch_num: channel ID (1 ... RIOCM_MAX_CHNUM, 0 = automatic)
 *
 * Return value: pointer to newly created channel object,
 *               or error-valued pointer
 */
static struct rio_channel *riocm_ch_alloc(u16 ch_num)
{
        int id;
        int start, end;
        struct rio_channel *ch;

        ch = kzalloc(sizeof(*ch), GFP_KERNEL);
        if (!ch)
                return ERR_PTR(-ENOMEM);

        if (ch_num) {
                /* If requested, try to obtain the specified channel ID */
                start = ch_num;
                end = ch_num + 1;
        } else {
                /* Obtain channel ID from the dynamic allocation range */
                start = chstart;
                end = RIOCM_MAX_CHNUM + 1;
        }

        idr_preload(GFP_KERNEL);
        spin_lock_bh(&idr_lock);
        id = idr_alloc_cyclic(&ch_idr, ch, start, end, GFP_NOWAIT);
        spin_unlock_bh(&idr_lock);
        idr_preload_end();

        if (id < 0) {
                kfree(ch);
                return ERR_PTR(id == -ENOSPC ? -EBUSY : id);
        }

        ch->id = (u16)id;
        ch->state = RIO_CM_IDLE;
        spin_lock_init(&ch->lock);
        INIT_LIST_HEAD(&ch->accept_queue);
        INIT_LIST_HEAD(&ch->ch_node);
        init_completion(&ch->comp);
        init_completion(&ch->comp_close);
        kref_init(&ch->ref);
        ch->rx_ring.head = 0;
        ch->rx_ring.tail = 0;
        ch->rx_ring.count = 0;
        ch->rx_ring.inuse_cnt = 0;

        return ch;
}

/*
 * riocm_ch_create - creates a new channel object and allocates ID for it
 * @ch_num: channel ID (1 ... RIOCM_MAX_CHNUM, 0 = automatic)
 *
 * Allocates and initializes a new channel object. If the parameter ch_num > 0
 * and is within the valid range, riocm_ch_create tries to allocate the
 * specified ID for the new channel. If ch_num = 0, channel ID will be assigned
 * automatically from the range (chstart ... RIOCM_MAX_CHNUM).
 * Module parameter 'chstart' defines start of an ID range available for dynamic
 * allocation. Range below 'chstart' is reserved for pre-defined ID numbers.
 * Available channel numbers are limited by 16-bit size of channel numbers used
 * in the packet header.
 *
 * Return value: PTR to rio_channel structure if successful (with channel number
 *               updated via pointer) or error-valued pointer if error.
 */
static struct rio_channel *riocm_ch_create(u16 *ch_num)
{
        struct rio_channel *ch = NULL;

        ch = riocm_ch_alloc(*ch_num);

        if (IS_ERR(ch))
                riocm_debug(CHOP, "Failed to allocate channel %d (err=%ld)",
                            *ch_num, PTR_ERR(ch));
        else
                *ch_num = ch->id;

        return ch;
}

/*
 * riocm_ch_free - channel object release routine
 * @ref: pointer to a channel's kref structure
 */
static void riocm_ch_free(struct kref *ref)
{
        struct rio_channel *ch = container_of(ref, struct rio_channel, ref);
        int i;

        riocm_debug(CHOP, "(ch_%d)", ch->id);

        if (ch->rx_ring.inuse_cnt) {
                for (i = 0;
                     i < RIOCM_RX_RING_SIZE && ch->rx_ring.inuse_cnt; i++) {
                        if (ch->rx_ring.inuse[i] != NULL) {
                                kfree(ch->rx_ring.inuse[i]);
                                ch->rx_ring.inuse_cnt--;
                        }
                }
        }

        if (ch->rx_ring.count)
                for (i = 0; i < RIOCM_RX_RING_SIZE && ch->rx_ring.count; i++) {
                        if (ch->rx_ring.buf[i] != NULL) {
                                kfree(ch->rx_ring.buf[i]);
                                ch->rx_ring.count--;
                        }
                }

        complete(&ch->comp_close);
}

static int riocm_send_close(struct rio_channel *ch)
{
        struct rio_ch_chan_hdr *hdr;
        int ret;

        /*
         * Send CH_CLOSE notification to the remote RapidIO device
         */

        hdr = kzalloc(sizeof(*hdr), GFP_KERNEL);
        if (hdr == NULL)
                return -ENOMEM;

        hdr->bhdr.src_id = htonl(ch->loc_destid);
        hdr->bhdr.dst_id = htonl(ch->rem_destid);
        hdr->bhdr.src_mbox = cmbox;
        hdr->bhdr.dst_mbox = cmbox;
        hdr->bhdr.type = RIO_CM_CHAN;
        hdr->ch_op = CM_CONN_CLOSE;
        hdr->dst_ch = htons(ch->rem_channel);
        hdr->src_ch = htons(ch->id);

        /* ATTN: the function call below relies on the fact that underlying
         * add_outb_message() routine copies TX data into its internal transfer
         * buffer. Needs to be reviewed if switched to direct buffer mode.
         */
        ret = riocm_post_send(ch->cmdev, ch->rdev, hdr, sizeof(*hdr));

        if (ret == -EBUSY && !riocm_queue_req(ch->cmdev, ch->rdev,
                                              hdr, sizeof(*hdr)))
                return 0;
        kfree(hdr);

        if (ret)
                riocm_error("ch(%d) send CLOSE failed (ret=%d)", ch->id, ret);

        return ret;
}

/*
 * riocm_ch_close - closes a channel object with specified ID (by local request)
 * @ch: channel to be closed
 */
static int riocm_ch_close(struct rio_channel *ch)
{
        unsigned long tmo = msecs_to_jiffies(3000);
        enum rio_cm_state state;
        long wret;
        int ret = 0;

        riocm_debug(CHOP, "ch_%d by %s(%d)",
                    ch->id, current->comm, task_pid_nr(current));

        state = riocm_exch(ch, RIO_CM_DESTROYING);
        if (state == RIO_CM_CONNECTED)
                riocm_send_close(ch);

        complete_all(&ch->comp);

        riocm_put_channel(ch);
        wret = wait_for_completion_interruptible_timeout(&ch->comp_close, tmo);

        riocm_debug(WAIT, "wait on %d returns %ld", ch->id, wret);

        if (wret == 0) {
                /* Timeout on wait occurred */
                riocm_debug(CHOP, "%s(%d) timed out waiting for ch %d",
                       current->comm, task_pid_nr(current), ch->id);
                ret = -ETIMEDOUT;
        } else if (wret == -ERESTARTSYS) {
                /* Wait_for_completion was interrupted by a signal */
                riocm_debug(CHOP, "%s(%d) wait for ch %d was interrupted",
                        current->comm, task_pid_nr(current), ch->id);
                ret = -EINTR;
        }

        if (!ret) {
                riocm_debug(CHOP, "ch_%d resources released", ch->id);
                kfree(ch);
        } else {
                riocm_debug(CHOP, "failed to release ch_%d resources", ch->id);
        }

        return ret;
}

/*
 * riocm_cdev_open() - Open character device
 */
static int riocm_cdev_open(struct inode *inode, struct file *filp)
{
        riocm_debug(INIT, "by %s(%d) filp=%p ",
                    current->comm, task_pid_nr(current), filp);

        if (list_empty(&cm_dev_list))
                return -ENODEV;

        return 0;
}

/*
 * riocm_cdev_release() - Release character device
 */
static int riocm_cdev_release(struct inode *inode, struct file *filp)
{
        struct rio_channel *ch, *_c;
        unsigned int i;
        LIST_HEAD(list);

        riocm_debug(EXIT, "by %s(%d) filp=%p",
                    current->comm, task_pid_nr(current), filp);

        /* Check if there are channels associated with this file descriptor */
        spin_lock_bh(&idr_lock);
        idr_for_each_entry(&ch_idr, ch, i) {
                if (ch && ch->filp == filp) {
                        riocm_debug(EXIT, "ch_%d not released by %s(%d)",
                                    ch->id, current->comm,
                                    task_pid_nr(current));
                        idr_remove(&ch_idr, ch->id);
                        list_add(&ch->ch_node, &list);
                }
        }
        spin_unlock_bh(&idr_lock);

        if (!list_empty(&list)) {
                list_for_each_entry_safe(ch, _c, &list, ch_node) {
                        list_del(&ch->ch_node);
                        riocm_ch_close(ch);
                }
        }

        return 0;
}

/*
 * cm_ep_get_list_size() - Reports number of endpoints in the network
 */
static int cm_ep_get_list_size(void __user *arg)
{
        u32 __user *p = arg;
        u32 mport_id;
        u32 count = 0;
        struct cm_dev *cm;

        if (get_user(mport_id, p))
                return -EFAULT;
        if (mport_id >= RIO_MAX_MPORTS)
                return -EINVAL;

        /* Find a matching cm_dev object */
        down_read(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (cm->mport->id == mport_id) {
                        count = cm->npeers;
                        up_read(&rdev_sem);
                        if (copy_to_user(arg, &count, sizeof(u32)))
                                return -EFAULT;
                        return 0;
                }
        }
        up_read(&rdev_sem);

        return -ENODEV;
}

/*
 * cm_ep_get_list() - Returns list of attached endpoints
 */
static int cm_ep_get_list(void __user *arg)
{
        struct cm_dev *cm;
        struct cm_peer *peer;
        u32 info[2];
        void *buf;
        u32 nent;
        u32 *entry_ptr;
        u32 i = 0;
        int ret = 0;

        if (copy_from_user(&info, arg, sizeof(info)))
                return -EFAULT;

        if (info[1] >= RIO_MAX_MPORTS || info[0] > RIOCM_MAX_EP_COUNT)
                return -EINVAL;

        /* Find a matching cm_dev object */
        down_read(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list)
                if (cm->mport->id == (u8)info[1])
                        goto found;

        up_read(&rdev_sem);
        return -ENODEV;

found:
        nent = min(info[0], cm->npeers);
        buf = kcalloc(nent + 2, sizeof(u32), GFP_KERNEL);
        if (!buf) {
                up_read(&rdev_sem);
                return -ENOMEM;
        }

        entry_ptr = (u32 *)((uintptr_t)buf + 2*sizeof(u32));

        list_for_each_entry(peer, &cm->peers, node) {
                *entry_ptr = (u32)peer->rdev->destid;
                entry_ptr++;
                if (++i == nent)
                        break;
        }
        up_read(&rdev_sem);

        ((u32 *)buf)[0] = i; /* report an updated number of entries */
        ((u32 *)buf)[1] = info[1]; /* put back an mport ID */
        if (copy_to_user(arg, buf, sizeof(u32) * (info[0] + 2)))
                ret = -EFAULT;

        kfree(buf);
        return ret;
}

/*
 * cm_mport_get_list() - Returns list of available local mport devices
 */
static int cm_mport_get_list(void __user *arg)
{
        int ret = 0;
        u32 entries;
        void *buf;
        struct cm_dev *cm;
        u32 *entry_ptr;
        int count = 0;

        if (copy_from_user(&entries, arg, sizeof(entries)))
                return -EFAULT;
        if (entries == 0 || entries > RIO_MAX_MPORTS)
                return -EINVAL;
        buf = kcalloc(entries + 1, sizeof(u32), GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        /* Scan all registered cm_dev objects */
        entry_ptr = (u32 *)((uintptr_t)buf + sizeof(u32));
        down_read(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (count++ < entries) {
                        *entry_ptr = (cm->mport->id << 16) |
                                      cm->mport->host_deviceid;
                        entry_ptr++;
                }
        }
        up_read(&rdev_sem);

        *((u32 *)buf) = count; /* report a real number of entries */
        if (copy_to_user(arg, buf, sizeof(u32) * (count + 1)))
                ret = -EFAULT;

        kfree(buf);
        return ret;
}

/*
 * cm_chan_create() - Create a message exchange channel
 */
static int cm_chan_create(struct file *filp, void __user *arg)
{
        u16 __user *p = arg;
        u16 ch_num;
        struct rio_channel *ch;

        if (get_user(ch_num, p))
                return -EFAULT;

        riocm_debug(CHOP, "ch_%d requested by %s(%d)",
                    ch_num, current->comm, task_pid_nr(current));
        ch = riocm_ch_create(&ch_num);
        if (IS_ERR(ch))
                return PTR_ERR(ch);

        ch->filp = filp;
        riocm_debug(CHOP, "ch_%d created by %s(%d)",
                    ch_num, current->comm, task_pid_nr(current));
        return put_user(ch_num, p);
}

/*
 * cm_chan_close() - Close channel
 * @filp:       Pointer to file object
 * @arg:        Channel to close
 */
static int cm_chan_close(struct file *filp, void __user *arg)
{
        u16 __user *p = arg;
        u16 ch_num;
        struct rio_channel *ch;

        if (get_user(ch_num, p))
                return -EFAULT;

        riocm_debug(CHOP, "ch_%d by %s(%d)",
                    ch_num, current->comm, task_pid_nr(current));

        spin_lock_bh(&idr_lock);
        ch = idr_find(&ch_idr, ch_num);
        if (!ch) {
                spin_unlock_bh(&idr_lock);
                return 0;
        }
        if (ch->filp != filp) {
                spin_unlock_bh(&idr_lock);
                return -EINVAL;
        }
        idr_remove(&ch_idr, ch->id);
        spin_unlock_bh(&idr_lock);

        return riocm_ch_close(ch);
}

/*
 * cm_chan_bind() - Bind channel
 * @arg:        Channel number
 */
static int cm_chan_bind(void __user *arg)
{
        struct rio_cm_channel chan;

        if (copy_from_user(&chan, arg, sizeof(chan)))
                return -EFAULT;
        if (chan.mport_id >= RIO_MAX_MPORTS)
                return -EINVAL;

        return riocm_ch_bind(chan.id, chan.mport_id, NULL);
}

/*
 * cm_chan_listen() - Listen on channel
 * @arg:        Channel number
 */
static int cm_chan_listen(void __user *arg)
{
        u16 __user *p = arg;
        u16 ch_num;

        if (get_user(ch_num, p))
                return -EFAULT;

        return riocm_ch_listen(ch_num);
}

/*
 * cm_chan_accept() - Accept incoming connection
 * @filp:       Pointer to file object
 * @arg:        Channel number
 */
static int cm_chan_accept(struct file *filp, void __user *arg)
{
        struct rio_cm_accept param;
        long accept_to;
        struct rio_channel *ch;

        if (copy_from_user(&param, arg, sizeof(param)))
                return -EFAULT;

        riocm_debug(CHOP, "on ch_%d by %s(%d)",
                    param.ch_num, current->comm, task_pid_nr(current));

        accept_to = param.wait_to ?
                        msecs_to_jiffies(param.wait_to) : 0;

        ch = riocm_ch_accept(param.ch_num, &param.ch_num, accept_to);
        if (IS_ERR(ch))
                return PTR_ERR(ch);
        ch->filp = filp;

        riocm_debug(CHOP, "new ch_%d for %s(%d)",
                    ch->id, current->comm, task_pid_nr(current));

        if (copy_to_user(arg, &param, sizeof(param)))
                return -EFAULT;
        return 0;
}

/*
 * cm_chan_connect() - Connect on channel
 * @arg:        Channel information
 */
static int cm_chan_connect(void __user *arg)
{
        struct rio_cm_channel chan;
        struct cm_dev *cm;
        struct cm_peer *peer;
        int ret = -ENODEV;

        if (copy_from_user(&chan, arg, sizeof(chan)))
                return -EFAULT;
        if (chan.mport_id >= RIO_MAX_MPORTS)
                return -EINVAL;

        down_read(&rdev_sem);

        /* Find matching cm_dev object */
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (cm->mport->id == chan.mport_id) {
                        ret = 0;
                        break;
                }
        }

        if (ret)
                goto err_out;

        if (chan.remote_destid >= RIO_ANY_DESTID(cm->mport->sys_size)) {
                ret = -EINVAL;
                goto err_out;
        }

        /* Find corresponding RapidIO endpoint device object */
        ret = -ENODEV;

        list_for_each_entry(peer, &cm->peers, node) {
                if (peer->rdev->destid == chan.remote_destid) {
                        ret = 0;
                        break;
                }
        }

        if (ret)
                goto err_out;

        up_read(&rdev_sem);

        return riocm_ch_connect(chan.id, cm, peer, chan.remote_channel);
err_out:
        up_read(&rdev_sem);
        return ret;
}

/*
 * cm_chan_msg_send() - Send a message through channel
 * @arg:        Outbound message information
 */
static int cm_chan_msg_send(void __user *arg)
{
        struct rio_cm_msg msg;
        void *buf;
        int ret;

        if (copy_from_user(&msg, arg, sizeof(msg)))
                return -EFAULT;
        if (msg.size > RIO_MAX_MSG_SIZE)
                return -EINVAL;

        buf = memdup_user((void __user *)(uintptr_t)msg.msg, msg.size);
        if (IS_ERR(buf))
                return PTR_ERR(buf);

        ret = riocm_ch_send(msg.ch_num, buf, msg.size);

        kfree(buf);
        return ret;
}

/*
 * cm_chan_msg_rcv() - Receive a message through channel
 * @arg:        Inbound message information
 */
static int cm_chan_msg_rcv(void __user *arg)
{
        struct rio_cm_msg msg;
        struct rio_channel *ch;
        void *buf;
        long rxto;
        int ret = 0, msg_size;

        if (copy_from_user(&msg, arg, sizeof(msg)))
                return -EFAULT;

        if (msg.ch_num == 0 || msg.size == 0)
                return -EINVAL;

        ch = riocm_get_channel(msg.ch_num);
        if (!ch)
                return -ENODEV;

        rxto = msg.rxto ? msecs_to_jiffies(msg.rxto) : MAX_SCHEDULE_TIMEOUT;

        ret = riocm_ch_receive(ch, &buf, rxto);
        if (ret)
                goto out;

        msg_size = min(msg.size, (u16)(RIO_MAX_MSG_SIZE));

        if (copy_to_user((void __user *)(uintptr_t)msg.msg, buf, msg_size))
                ret = -EFAULT;

        riocm_ch_free_rxbuf(ch, buf);
out:
        riocm_put_channel(ch);
        return ret;
}

/*
 * riocm_cdev_ioctl() - IOCTL requests handler
 */
static long
riocm_cdev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        switch (cmd) {
        case RIO_CM_EP_GET_LIST_SIZE:
                return cm_ep_get_list_size((void __user *)arg);
        case RIO_CM_EP_GET_LIST:
                return cm_ep_get_list((void __user *)arg);
        case RIO_CM_CHAN_CREATE:
                return cm_chan_create(filp, (void __user *)arg);
        case RIO_CM_CHAN_CLOSE:
                return cm_chan_close(filp, (void __user *)arg);
        case RIO_CM_CHAN_BIND:
                return cm_chan_bind((void __user *)arg);
        case RIO_CM_CHAN_LISTEN:
                return cm_chan_listen((void __user *)arg);
        case RIO_CM_CHAN_ACCEPT:
                return cm_chan_accept(filp, (void __user *)arg);
        case RIO_CM_CHAN_CONNECT:
                return cm_chan_connect((void __user *)arg);
        case RIO_CM_CHAN_SEND:
                return cm_chan_msg_send((void __user *)arg);
        case RIO_CM_CHAN_RECEIVE:
                return cm_chan_msg_rcv((void __user *)arg);
        case RIO_CM_MPORT_GET_LIST:
                return cm_mport_get_list((void __user *)arg);
        default:
                break;
        }

        return -EINVAL;
}

static const struct file_operations riocm_cdev_fops = {
        .owner          = THIS_MODULE,
        .open           = riocm_cdev_open,
        .release        = riocm_cdev_release,
        .unlocked_ioctl = riocm_cdev_ioctl,
};

/*
 * riocm_add_dev - add new remote RapidIO device into channel management core
 * @dev: device object associated with RapidIO device
 * @sif: subsystem interface
 *
 * Adds the specified RapidIO device (if applicable) into peers list of
 * the corresponding channel management device (cm_dev).
 */
static int riocm_add_dev(struct device *dev, struct subsys_interface *sif)
{
        struct cm_peer *peer;
        struct rio_dev *rdev = to_rio_dev(dev);
        struct cm_dev *cm;

        /* Check if the remote device has capabilities required to support CM */
        if (!dev_cm_capable(rdev))
                return 0;

        riocm_debug(RDEV, "(%s)", rio_name(rdev));

        peer = kmalloc(sizeof(*peer), GFP_KERNEL);
        if (!peer)
                return -ENOMEM;

        /* Find a corresponding cm_dev object */
        down_write(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (cm->mport == rdev->net->hport)
                        goto found;
        }

        up_write(&rdev_sem);
        kfree(peer);
        return -ENODEV;

found:
        peer->rdev = rdev;
        list_add_tail(&peer->node, &cm->peers);
        cm->npeers++;

        up_write(&rdev_sem);
        return 0;
}

/*
 * riocm_remove_dev - remove remote RapidIO device from channel management core
 * @dev: device object associated with RapidIO device
 * @sif: subsystem interface
 *
 * Removes the specified RapidIO device (if applicable) from peers list of
 * the corresponding channel management device (cm_dev).
 */
static void riocm_remove_dev(struct device *dev, struct subsys_interface *sif)
{
        struct rio_dev *rdev = to_rio_dev(dev);
        struct cm_dev *cm;
        struct cm_peer *peer;
        struct rio_channel *ch, *_c;
        unsigned int i;
        bool found = false;
        LIST_HEAD(list);

        /* Check if the remote device has capabilities required to support CM */
        if (!dev_cm_capable(rdev))
                return;

        riocm_debug(RDEV, "(%s)", rio_name(rdev));

        /* Find matching cm_dev object */
        down_write(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (cm->mport == rdev->net->hport) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                up_write(&rdev_sem);
                return;
        }

        /* Remove remote device from the list of peers */
        found = false;
        list_for_each_entry(peer, &cm->peers, node) {
                if (peer->rdev == rdev) {
                        riocm_debug(RDEV, "removing peer %s", rio_name(rdev));
                        found = true;
                        list_del(&peer->node);
                        cm->npeers--;
                        kfree(peer);
                        break;
                }
        }

        up_write(&rdev_sem);

        if (!found)
                return;

        /*
         * Release channels associated with this peer
         */

        spin_lock_bh(&idr_lock);
        idr_for_each_entry(&ch_idr, ch, i) {
                if (ch && ch->rdev == rdev) {
                        if (atomic_read(&rdev->state) != RIO_DEVICE_SHUTDOWN)
                                riocm_exch(ch, RIO_CM_DISCONNECT);
                        idr_remove(&ch_idr, ch->id);
                        list_add(&ch->ch_node, &list);
                }
        }
        spin_unlock_bh(&idr_lock);

        if (!list_empty(&list)) {
                list_for_each_entry_safe(ch, _c, &list, ch_node) {
                        list_del(&ch->ch_node);
                        riocm_ch_close(ch);
                }
        }
}

/*
 * riocm_cdev_add() - Create rio_cm char device
 * @devno: device number assigned to device (MAJ + MIN)
 */
static int riocm_cdev_add(dev_t devno)
{
        int ret;

        cdev_init(&riocm_cdev.cdev, &riocm_cdev_fops);
        riocm_cdev.cdev.owner = THIS_MODULE;
        ret = cdev_add(&riocm_cdev.cdev, devno, 1);
        if (ret < 0) {
                riocm_error("Cannot register a device with error %d", ret);
                return ret;
        }

        riocm_cdev.dev = device_create(dev_class, NULL, devno, NULL, DEV_NAME);
        if (IS_ERR(riocm_cdev.dev)) {
                cdev_del(&riocm_cdev.cdev);
                return PTR_ERR(riocm_cdev.dev);
        }

        riocm_debug(MPORT, "Added %s cdev(%d:%d)",
                    DEV_NAME, MAJOR(devno), MINOR(devno));

        return 0;
}

/*
 * riocm_add_mport - add new local mport device into channel management core
 * @dev: device object associated with mport
 * @class_intf: class interface
 *
 * When a new mport device is added, CM immediately reserves inbound and
 * outbound RapidIO mailboxes that will be used.
 */
static int riocm_add_mport(struct device *dev,
                           struct class_interface *class_intf)
{
        int rc;
        int i;
        struct cm_dev *cm;
        struct rio_mport *mport = to_rio_mport(dev);

        riocm_debug(MPORT, "add mport %s", mport->name);

        cm = kzalloc(sizeof(*cm), GFP_KERNEL);
        if (!cm)
                return -ENOMEM;

        cm->mport = mport;

        rc = rio_request_outb_mbox(mport, cm, cmbox,
                                   RIOCM_TX_RING_SIZE, riocm_outb_msg_event);
        if (rc) {
                riocm_error("failed to allocate OBMBOX_%d on %s",
                            cmbox, mport->name);
                kfree(cm);
                return -ENODEV;
        }

        rc = rio_request_inb_mbox(mport, cm, cmbox,
                                  RIOCM_RX_RING_SIZE, riocm_inb_msg_event);
        if (rc) {
                riocm_error("failed to allocate IBMBOX_%d on %s",
                            cmbox, mport->name);
                rio_release_outb_mbox(mport, cmbox);
                kfree(cm);
                return -ENODEV;
        }

        /*
         * Allocate and register inbound messaging buffers to be ready
         * to receive channel and system management requests
         */
        for (i = 0; i < RIOCM_RX_RING_SIZE; i++)
                cm->rx_buf[i] = NULL;

        cm->rx_slots = RIOCM_RX_RING_SIZE;
        mutex_init(&cm->rx_lock);
        riocm_rx_fill(cm, RIOCM_RX_RING_SIZE);
        cm->rx_wq = create_workqueue(DRV_NAME "/rxq");
        if (!cm->rx_wq) {
                riocm_error("failed to allocate IBMBOX_%d on %s",
                            cmbox, mport->name);
                rio_release_outb_mbox(mport, cmbox);
                kfree(cm);
                return -ENOMEM;
        }

        INIT_WORK(&cm->rx_work, rio_ibmsg_handler);

        cm->tx_slot = 0;
        cm->tx_cnt = 0;
        cm->tx_ack_slot = 0;
        spin_lock_init(&cm->tx_lock);

        INIT_LIST_HEAD(&cm->peers);
        cm->npeers = 0;
        INIT_LIST_HEAD(&cm->tx_reqs);

        down_write(&rdev_sem);
        list_add_tail(&cm->list, &cm_dev_list);
        up_write(&rdev_sem);

        return 0;
}

/*
 * riocm_remove_mport - remove local mport device from channel management core
 * @dev: device object associated with mport
 * @class_intf: class interface
 *
 * Removes a local mport device from the list of registered devices that provide
 * channel management services. Returns an error if the specified mport is not
 * registered with the CM core.
 */
static void riocm_remove_mport(struct device *dev,
                               struct class_interface *class_intf)
{
        struct rio_mport *mport = to_rio_mport(dev);
        struct cm_dev *cm;
        struct cm_peer *peer, *temp;
        struct rio_channel *ch, *_c;
        unsigned int i;
        bool found = false;
        LIST_HEAD(list);

        riocm_debug(MPORT, "%s", mport->name);

        /* Find a matching cm_dev object */
        down_write(&rdev_sem);
        list_for_each_entry(cm, &cm_dev_list, list) {
                if (cm->mport == mport) {
                        list_del(&cm->list);
                        found = true;
                        break;
                }
        }
        up_write(&rdev_sem);
        if (!found)
                return;

        flush_workqueue(cm->rx_wq);
        destroy_workqueue(cm->rx_wq);

        /* Release channels bound to this mport */
        spin_lock_bh(&idr_lock);
        idr_for_each_entry(&ch_idr, ch, i) {
                if (ch->cmdev == cm) {
                        riocm_debug(RDEV, "%s drop ch_%d",
                                    mport->name, ch->id);
                        idr_remove(&ch_idr, ch->id);
                        list_add(&ch->ch_node, &list);
                }
        }
        spin_unlock_bh(&idr_lock);

        if (!list_empty(&list)) {
                list_for_each_entry_safe(ch, _c, &list, ch_node) {
                        list_del(&ch->ch_node);
                        riocm_ch_close(ch);
                }
        }

        rio_release_inb_mbox(mport, cmbox);
        rio_release_outb_mbox(mport, cmbox);

        /* Remove and free peer entries */
        if (!list_empty(&cm->peers))
                riocm_debug(RDEV, "ATTN: peer list not empty");
        list_for_each_entry_safe(peer, temp, &cm->peers, node) {
                riocm_debug(RDEV, "removing peer %s", rio_name(peer->rdev));
                list_del(&peer->node);
                kfree(peer);
        }

        riocm_rx_free(cm);
        kfree(cm);
        riocm_debug(MPORT, "%s done", mport->name);
}

static int rio_cm_shutdown(struct notifier_block *nb, unsigned long code,
        void *unused)
{
        struct rio_channel *ch;
        unsigned int i;
        LIST_HEAD(list);

        riocm_debug(EXIT, ".");

        /*
         * If there are any channels left in connected state send
         * close notification to the connection partner.
         * First build a list of channels that require a closing
         * notification because function riocm_send_close() should
         * be called outside of spinlock protected code.
         */
        spin_lock_bh(&idr_lock);
        idr_for_each_entry(&ch_idr, ch, i) {
                if (ch->state == RIO_CM_CONNECTED) {
                        riocm_debug(EXIT, "close ch %d", ch->id);
                        idr_remove(&ch_idr, ch->id);
                        list_add(&ch->ch_node, &list);
                }
        }
        spin_unlock_bh(&idr_lock);

        list_for_each_entry(ch, &list, ch_node)
                riocm_send_close(ch);

        return NOTIFY_DONE;
}

/*
 * riocm_interface handles addition/removal of remote RapidIO devices
 */
static struct subsys_interface riocm_interface = {
        .name           = "rio_cm",
        .subsys         = &rio_bus_type,
        .add_dev        = riocm_add_dev,
        .remove_dev     = riocm_remove_dev,
};

/*
 * rio_mport_interface handles addition/removal local mport devices
 */
static struct class_interface rio_mport_interface __refdata = {
        .class = &rio_mport_class,
        .add_dev = riocm_add_mport,
        .remove_dev = riocm_remove_mport,
};

static struct notifier_block rio_cm_notifier = {
        .notifier_call = rio_cm_shutdown,
};

static int __init riocm_init(void)
{
        int ret;

        /* Create device class needed by udev */
        dev_class = class_create(THIS_MODULE, DRV_NAME);
        if (IS_ERR(dev_class)) {
                riocm_error("Cannot create " DRV_NAME " class");
                return PTR_ERR(dev_class);
        }

        ret = alloc_chrdev_region(&dev_number, 0, 1, DRV_NAME);
        if (ret) {
                class_destroy(dev_class);
                return ret;
        }

        dev_major = MAJOR(dev_number);
        dev_minor_base = MINOR(dev_number);
        riocm_debug(INIT, "Registered class with %d major", dev_major);

        /*
         * Register as rapidio_port class interface to get notifications about
         * mport additions and removals.
         */
        ret = class_interface_register(&rio_mport_interface);
        if (ret) {
                riocm_error("class_interface_register error: %d", ret);
                goto err_reg;
        }

        /*
         * Register as RapidIO bus interface to get notifications about
         * addition/removal of remote RapidIO devices.
         */
        ret = subsys_interface_register(&riocm_interface);
        if (ret) {
                riocm_error("subsys_interface_register error: %d", ret);
                goto err_cl;
        }

        ret = register_reboot_notifier(&rio_cm_notifier);
        if (ret) {
                riocm_error("failed to register reboot notifier (err=%d)", ret);
                goto err_sif;
        }

        ret = riocm_cdev_add(dev_number);
        if (ret) {
                unregister_reboot_notifier(&rio_cm_notifier);
                ret = -ENODEV;
                goto err_sif;
        }

        return 0;
err_sif:
        subsys_interface_unregister(&riocm_interface);
err_cl:
        class_interface_unregister(&rio_mport_interface);
err_reg:
        unregister_chrdev_region(dev_number, 1);
        class_destroy(dev_class);
        return ret;
}

static void __exit riocm_exit(void)
{
        riocm_debug(EXIT, "enter");
        unregister_reboot_notifier(&rio_cm_notifier);
        subsys_interface_unregister(&riocm_interface);
        class_interface_unregister(&rio_mport_interface);
        idr_destroy(&ch_idr);

        device_unregister(riocm_cdev.dev);
        cdev_del(&(riocm_cdev.cdev));

        class_destroy(dev_class);
        unregister_chrdev_region(dev_number, 1);
}

late_initcall(riocm_init);
module_exit(riocm_exit);