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/*

 * QEMU Random Number Generator Backend

 *

 * Copyright IBM, Corp. 2012

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2 or later.

 * See the COPYING file in the top-level directory.

 */

#include "sysemu/rng.h"

#include "sysemu/char.h"

#include "qapi/qmp/qerror.h"

#include "hw/qdev.h" /* just for DEFINE_PROP_CHR */

#define TYPE_RNG_EGD "rng-egd"

#define RNG_EGD(obj) OBJECT_CHECK(RngEgd, (obj), TYPE_RNG_EGD)

typedef struct RngEgd

{

    RngBackend parent;

    CharDriverState *chr;

    char *chr_name;

    GSList *requests;

} RngEgd;

typedef struct RngRequest

{

    EntropyReceiveFunc *receive_entropy;

    uint8_t *data;

    void *opaque;

    size_t offset;

    size_t size;

} RngRequest;

static void rng_egd_request_entropy(RngBackend *b, size_t size,

                                    EntropyReceiveFunc *receive_entropy,

                                    void *opaque)

{

    RngEgd *s = RNG_EGD(b);

    RngRequest *req;

    req = g_malloc(sizeof(*req));

    req->offset = 0;

    req->size = size;

    req->receive_entropy = receive_entropy;

    req->opaque = opaque;

    req->data = g_malloc(req->size);

    while (size > 0) {

        uint8_t header[2];

        uint8_t len = MIN(size, 255);

        /* synchronous entropy request */

        header[0] = 0x02;

        header[1] = len;

        qemu_chr_fe_write(s->chr, header, sizeof(header));

        size -= len;

    }

    s->requests = g_slist_append(s->requests, req);

}

static void rng_egd_free_request(RngRequest *req)

{

    g_free(req->data);

    g_free(req);

}

static int rng_egd_chr_can_read(void *opaque)

{

    RngEgd *s = RNG_EGD(opaque);

    GSList *i;

    int size = 0;

    for (i = s->requests; i; i = i->next) {

        RngRequest *req = i->data;

        size += req->size - req->offset;

    }

    return size;

}

static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)

{

    RngEgd *s = RNG_EGD(opaque);

    size_t buf_offset = 0;

    while (size > 0 && s->requests) {

        RngRequest *req = s->requests->data;

        int len = MIN(size, req->size - req->offset);

        memcpy(req->data + req->offset, buf + buf_offset, len);

        buf_offset += len;

        req->offset += len;

        size -= len;

        if (req->offset == req->size) {

            s->requests = g_slist_remove_link(s->requests, s->requests);

            req->receive_entropy(req->opaque, req->data, req->size);

            rng_egd_free_request(req);

        }

    }

}

static void rng_egd_free_requests(RngEgd *s)

{

    GSList *i;

    for (i = s->requests; i; i = i->next) {

        rng_egd_free_request(i->data);

    }

    g_slist_free(s->requests);

    s->requests = NULL;

}

static void rng_egd_cancel_requests(RngBackend *b)

{

    RngEgd *s = RNG_EGD(b);

    /* We simply delete the list of pending requests.  If there is data in the 

     * queue waiting to be read, this is okay, because there will always be

     * more data than we requested originally

     */

    rng_egd_free_requests(s);

}

static void rng_egd_opened(RngBackend *b, Error **errp)

{

    RngEgd *s = RNG_EGD(b);

    if (s->chr_name == NULL) {

        error_set(errp, QERR_INVALID_PARAMETER_VALUE,

                  "chardev", "a valid character device");

        return;

    }

    s->chr = qemu_chr_find(s->chr_name);

    if (s->chr == NULL) {

        error_set(errp, QERR_DEVICE_NOT_FOUND, s->chr_name);

        return;

    }

    if (qemu_chr_fe_claim(s->chr) != 0) {

        error_set(errp, QERR_DEVICE_IN_USE, s->chr_name);

        return;

    }

    /* FIXME we should resubmit pending requests when the CDS reconnects. */

    qemu_chr_add_handlers(s->chr, rng_egd_chr_can_read, rng_egd_chr_read,

                          NULL, s);

}

static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)

{

    RngBackend *b = RNG_BACKEND(obj);

    RngEgd *s = RNG_EGD(b);

    if (b->opened) {

        error_set(errp, QERR_PERMISSION_DENIED);

    } else {

        s->chr_name = g_strdup(value);

    }

}

static char *rng_egd_get_chardev(Object *obj, Error **errp)

{

    RngEgd *s = RNG_EGD(obj);

    if (s->chr && s->chr->label) {

        return g_strdup(s->chr->label);

    }

    return NULL;

}

static void rng_egd_init(Object *obj)

{

    object_property_add_str(obj, "chardev",

                            rng_egd_get_chardev, rng_egd_set_chardev,

                            NULL);

}

static void rng_egd_finalize(Object *obj)

{

    RngEgd *s = RNG_EGD(obj);

    if (s->chr) {

        qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);

        qemu_chr_fe_release(s->chr);

    }

    g_free(s->chr_name);

    rng_egd_free_requests(s);

}

static void rng_egd_class_init(ObjectClass *klass, void *data)

{

    RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);

    rbc->request_entropy = rng_egd_request_entropy;

    rbc->cancel_requests = rng_egd_cancel_requests;

    rbc->opened = rng_egd_opened;

}

static const TypeInfo rng_egd_info = {

    .name = TYPE_RNG_EGD,

    .parent = TYPE_RNG_BACKEND,

    .instance_size = sizeof(RngEgd),

    .class_init = rng_egd_class_init,

    .instance_init = rng_egd_init,

    .instance_finalize = rng_egd_finalize,

};

static void register_types(void)

{

    type_register_static(&rng_egd_info);

}

type_init(register_types);