/*
 *  Copyright (C) International Business Machines  Corp., 2005
 *  Author(s): Anthony Liguori <aliguori@us.ibm.com>
 *
 *  Copyright (C) Red Hat 2007
 *
 *  Xen Console
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; under version 2 of the License.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "qemu/osdep.h"
#include <sys/select.h>
#include <termios.h>

#include "qapi/error.h"
#include "hw/hw.h"
#include "chardev/char-fe.h"
#include "hw/xen/xen-legacy-backend.h"

#include <xen/io/console.h>

struct buffer {
    uint8_t *data;
    size_t consumed;
    size_t size;
    size_t capacity;
    size_t max_capacity;
};

struct XenConsole {
    struct XenLegacyDevice  xendev;  /* must be first */
    struct buffer     buffer;
    char              console[XEN_BUFSIZE];
    int               ring_ref;
    void              *sring;
    CharBackend       chr;
    int               backlog;
};

static void buffer_append(struct XenConsole *con)
{
    struct buffer *buffer = &con->buffer;
    XENCONS_RING_IDX cons, prod, size;
    struct xencons_interface *intf = con->sring;

    cons = intf->out_cons;
    prod = intf->out_prod;
    xen_mb();

    size = prod - cons;
    if ((size == 0) || (size > sizeof(intf->out)))
        return;

    if ((buffer->capacity - buffer->size) < size) {
        buffer->capacity += (size + 1024);
        buffer->data = g_realloc(buffer->data, buffer->capacity);
    }

    while (cons != prod)
        buffer->data[buffer->size++] = intf->out[
            MASK_XENCONS_IDX(cons++, intf->out)];

    xen_mb();
    intf->out_cons = cons;
    xen_pv_send_notify(&con->xendev);

    if (buffer->max_capacity &&
        buffer->size > buffer->max_capacity) {
        /* Discard the middle of the data. */

        size_t over = buffer->size - buffer->max_capacity;
        uint8_t *maxpos = buffer->data + buffer->max_capacity;

        memmove(maxpos - over, maxpos, over);
        buffer->data = g_realloc(buffer->data, buffer->max_capacity);
        buffer->size = buffer->capacity = buffer->max_capacity;

        if (buffer->consumed > buffer->max_capacity - over)
            buffer->consumed = buffer->max_capacity - over;
    }
}

static void buffer_advance(struct buffer *buffer, size_t len)
{
    buffer->consumed += len;
    if (buffer->consumed == buffer->size) {
        buffer->consumed = 0;
        buffer->size = 0;
    }
}

static int ring_free_bytes(struct XenConsole *con)
{
    struct xencons_interface *intf = con->sring;
    XENCONS_RING_IDX cons, prod, space;

    cons = intf->in_cons;
    prod = intf->in_prod;
    xen_mb();

    space = prod - cons;
    if (space > sizeof(intf->in))
        return 0; /* ring is screwed: ignore it */

    return (sizeof(intf->in) - space);
}

static int xencons_can_receive(void *opaque)
{
    struct XenConsole *con = opaque;
    return ring_free_bytes(con);
}

static void xencons_receive(void *opaque, const uint8_t *buf, int len)
{
    struct XenConsole *con = opaque;
    struct xencons_interface *intf = con->sring;
    XENCONS_RING_IDX prod;
    int i, max;

    max = ring_free_bytes(con);
    /* The can_receive() func limits this, but check again anyway */
    if (max < len)
        len = max;

    prod = intf->in_prod;
    for (i = 0; i < len; i++) {
        intf->in[MASK_XENCONS_IDX(prod++, intf->in)] =
            buf[i];
    }
    xen_wmb();
    intf->in_prod = prod;
    xen_pv_send_notify(&con->xendev);
}

static void xencons_send(struct XenConsole *con)
{
    ssize_t len, size;

    size = con->buffer.size - con->buffer.consumed;
    if (qemu_chr_fe_backend_connected(&con->chr)) {
        len = qemu_chr_fe_write(&con->chr,
                                con->buffer.data + con->buffer.consumed,
                                size);
    } else {
        len = size;
    }
    if (len < 1) {
        if (!con->backlog) {
            con->backlog = 1;
            xen_pv_printf(&con->xendev, 1,
                          "backlog piling up, nobody listening?\n");
        }
    } else {
        buffer_advance(&con->buffer, len);
        if (con->backlog && len == size) {
            con->backlog = 0;
            xen_pv_printf(&con->xendev, 1, "backlog is gone\n");
        }
    }
}

/* -------------------------------------------------------------------- */

static int con_init(struct XenLegacyDevice *xendev)
{
    struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);
    char *type, *dom, label[32];
    int ret = 0;
    const char *output;

    /* setup */
    dom = xs_get_domain_path(xenstore, con->xendev.dom);
    if (!xendev->dev) {
        snprintf(con->console, sizeof(con->console), "%s/console", dom);
    } else {
        snprintf(con->console, sizeof(con->console), "%s/device/console/%d", dom, xendev->dev);
    }
    free(dom);

    type = xenstore_read_str(con->console, "type");
    if (!type || strcmp(type, "ioemu") != 0) {
        xen_pv_printf(xendev, 1, "not for me (type=%s)\n", type);
        ret = -1;
        goto out;
    }

    output = xenstore_read_str(con->console, "output");

    /* no Xen override, use qemu output device */
    if (output == NULL) {
        if (con->xendev.dev) {
            qemu_chr_fe_init(&con->chr, serial_hd(con->xendev.dev),
                             &error_abort);
        }
    } else {
        snprintf(label, sizeof(label), "xencons%d", con->xendev.dev);
        qemu_chr_fe_init(&con->chr,
                         /*
                          * FIXME: sure we want to support implicit
                          * muxed monitors here?
                          */
                         qemu_chr_new_mux_mon(label, output, NULL),
                         &error_abort);
    }

    xenstore_store_pv_console_info(con->xendev.dev,
                                   qemu_chr_fe_get_driver(&con->chr));

out:
    g_free(type);
    return ret;
}

static int con_initialise(struct XenLegacyDevice *xendev)
{
    struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);
    int limit;

    if (xenstore_read_int(con->console, "ring-ref", &con->ring_ref) == -1)
        return -1;
    if (xenstore_read_int(con->console, "port", &con->xendev.remote_port) == -1)
        return -1;
    if (xenstore_read_int(con->console, "limit", &limit) == 0)
        con->buffer.max_capacity = limit;

    if (!xendev->dev) {
        xen_pfn_t mfn = con->ring_ref;
        con->sring = xenforeignmemory_map(xen_fmem, con->xendev.dom,
                                          PROT_READ | PROT_WRITE,
                                          1, &mfn, NULL);
    } else {
        con->sring = xen_be_map_grant_ref(xendev, con->ring_ref,
                                          PROT_READ | PROT_WRITE);
    }
    if (!con->sring)
        return -1;

    xen_be_bind_evtchn(&con->xendev);
    qemu_chr_fe_set_handlers(&con->chr, xencons_can_receive,
                             xencons_receive, NULL, NULL, con, NULL, true);

    xen_pv_printf(xendev, 1,
                  "ring mfn %d, remote port %d, local port %d, limit %zd\n",
                  con->ring_ref,
                  con->xendev.remote_port,
                  con->xendev.local_port,
                  con->buffer.max_capacity);
    return 0;
}

static void con_disconnect(struct XenLegacyDevice *xendev)
{
    struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);

    qemu_chr_fe_deinit(&con->chr, false);
    xen_pv_unbind_evtchn(&con->xendev);

    if (con->sring) {
        if (!xendev->dev) {
            xenforeignmemory_unmap(xen_fmem, con->sring, 1);
        } else {
            xen_be_unmap_grant_ref(xendev, con->sring);
        }
        con->sring = NULL;
    }
}

static void con_event(struct XenLegacyDevice *xendev)
{
    struct XenConsole *con = container_of(xendev, struct XenConsole, xendev);

    buffer_append(con);
    if (con->buffer.size - con->buffer.consumed)
        xencons_send(con);
}

/* -------------------------------------------------------------------- */

struct XenDevOps xen_console_ops = {
    .size       = sizeof(struct XenConsole),
    .flags      = DEVOPS_FLAG_IGNORE_STATE|DEVOPS_FLAG_NEED_GNTDEV,
    .init       = con_init,
    .initialise = con_initialise,
    .event      = con_event,
    .disconnect = con_disconnect,
};