/*      $OpenBSD: acpihve.c,v 1.4 2022/04/06 18:59:27 naddy Exp $       */

/*
 * Copyright (c) 2017 Jonathan Gray <jsg@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/device.h>

#include <dev/acpi/acpireg.h>
#include <dev/acpi/acpivar.h>

int      acpihve_match(struct device *, void *, void *);
void     acpihve_attach(struct device *, struct device *, void *);

struct acpi_oem0 {
        struct acpi_table_header        hdr;
        uint32_t                        entropy[16];
} __packed;

struct acpihve_softc {
        struct device                   sc_dev;
};

const struct cfattach acpihve_ca = {
        sizeof(struct acpihve_softc), acpihve_match, acpihve_attach
};

struct cfdriver acpihve_cd = {
        NULL, "acpihve", DV_DULL
};

int      acpihve_attached;

int
acpihve_match(struct device *parent, void *match, void *aux)
{
        struct acpi_attach_args *aaa = aux;
        struct acpi_table_header *hdr;

        /*
         * If we do not have a table, it is not us; attach only once
         */
        if (acpihve_attached || aaa->aaa_table == NULL)
                return (0);

        hdr = (struct acpi_table_header *)aaa->aaa_table;
        if (memcmp(hdr->signature, "OEM0", 4) != 0 ||
            memcmp(hdr->oemid, "VRTUAL", 6) != 0 ||
            memcmp(hdr->oemtableid, "MICROSFT", 8) != 0)
                return (0);

        return (1);
}

void
acpihve_attach(struct device *parent, struct device *self, void *aux)
{
        struct acpi_attach_args *aaa = aux;
        struct acpi_oem0 *oem0 = (struct acpi_oem0 *)aaa->aaa_table;
        int i;

        acpihve_attached++;

        if (oem0->hdr.length != sizeof(*oem0)) {
                printf(": unexpected table length %u\n", oem0->hdr.length);
                return;
        }

        /* 64 bytes of entropy from OEM0 table */
        for (i = 0; i < nitems(oem0->entropy); i++)
                enqueue_randomness(oem0->entropy[i]);

        printf("\n");
}