/*
 * Copyright 2004-2006, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
 * Distributed under the terms of the MIT License.
 */


#include <KernelExport.h>
#include <vm/vm_types.h>

#include <arch/x86/bios.h>


//#define TRACE_BIOS
#ifdef TRACE_BIOS
#       define TRACE(x) dprintf x
#else
#       define TRACE(x) ;
#endif


struct smbios {
        uint32          anchor_string;
        uint8           entry_point_checksum;
        uint8           entry_point_length;
        struct {
                uint8   major;
                uint8   minor;
        } version;
        uint16          maximum_size;
        uint8           formatted_area[5];

        // this part is the legacy DMI compatible structure
        uint8           dmi_anchor_string[5];
        uint8           intermediate_checksum;
        uint16          structure_table_size;
        uint32          structure_table;
        uint16          num_structures;
        uint8           bcd_revision;
} _PACKED;

struct bios32 {
        uint32          anchor_string;
        uint32          service_directory;
        uint8           revision;
        uint8           size;   // in "paragraph" (16 byte) units
        uint8           checksum;
        uint8           _reserved[5];
};

enum {
        BIOS32  = '_23_',
        SMBIOS  = '_MS_',
        DMI             = '_IMD',
};


addr_t gBiosBase;
static addr_t sBios32ServiceDirectory;


static bool
check_checksum(addr_t base, size_t length)
{
        uint8 *bytes = (uint8 *)base;
        uint8 sum = 0;

        for (uint32 i = 0; i < length; i++)
                sum += bytes[i];

        return sum == 0;
}


//      #pragma mark -
//      public functions


/**     This function fills the provided bios32_service structure with
 *      the values that identify BIOS service.
 *      Returns B_OK on successful completion, otherwise B_ERROR if
 *      the BIOS32 service directory is not available, or B_BAD_VALUE
 *      in case the identifier is not known or present.
 */

extern "C" status_t
get_bios32_service(uint32 identifier, struct bios32_service *service)
{
        TRACE(("get_bios32_service(identifier = %#lx)\n", identifier));

        if (sBios32ServiceDirectory == 0)
                return B_ERROR;

        uint32 eax = 0, ebx = 0, ecx = 0, edx = 0;

        asm("movl       %4, %%eax;              "       // set service parameters
                "xorl   %%ebx, %%ebx;   "
                "movl   %5, %%ecx;              "
                "pushl  %%cs;                   "       // emulate far call by register
                "call   *%%ecx;                 "
                "movl   %%eax, %0;              "       // save return values
                "movl   %%ebx, %1;              "
                "movl   %%ecx, %2;              "
                "movl   %%edx, %3;              "
                : "=m" (eax), "=m" (ebx), "=m" (ecx), "=m" (edx)
                : "m" (identifier), "m" (sBios32ServiceDirectory)
                : "eax", "ebx", "ecx", "edx", "memory");

        if ((eax & 0xff) != 0)
                return B_BAD_VALUE;

        service->base = ebx;
        service->size = ecx;
        service->offset = edx;

        return B_OK;
}


extern "C" status_t
bios_init(void)
{
        // map BIOS area 0xe0000 - 0xfffff
        area_id biosArea = map_physical_memory("pc bios", 0xe0000, 0x20000,
                B_ANY_KERNEL_ADDRESS | B_WRITE_BACK_MEMORY,
                B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA, (void **)&gBiosBase);
        if (biosArea < 0)
                return biosArea;

        TRACE(("PC BIOS mapped to %p\n", (void *)gBiosBase));

        // ToDo: add driver settings support to disable the services below

        // search for available BIOS services

        addr_t base = gBiosBase;
        addr_t end = base + 0x20000;

        while (base < end) {
                switch (*(uint32 *)base) {
                        case BIOS32:
                                if (check_checksum(base, sizeof(struct bios32))) {
                                        struct bios32 *bios32 = (struct bios32 *)base;

                                        TRACE(("bios32 revision %d\n", bios32->revision));
                                        TRACE(("bios32 service directory at: %lx\n", bios32->service_directory));

                                        if (bios32->service_directory >= 0xe0000
                                                && bios32->service_directory <= 0xfffff)
                                                sBios32ServiceDirectory = gBiosBase - 0xe0000 + bios32->service_directory;
                                }
                                break;
                        case SMBIOS:
                                // SMBIOS contains the legacy DMI structure, so we have to
                                // make sure it won't be found
                                base += 16;
                                TRACE(("probably found SMBIOS structure.\n"));
                                break;
                        case DMI:
                                TRACE(("probably found DMI legacy structure.\n"));
                                break;
                }

                // get on to next "paragraph"
                base += 16;
        }

        return B_OK;
}