mirror of https://github.com/tongzx/nt5src
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
106 lines
1.9 KiB
106 lines
1.9 KiB
/* xmsa20.c - A20 related XMS routines
|
|
*
|
|
* XMSA20
|
|
*
|
|
* Modification History:
|
|
*
|
|
* Sudeepb 15-May-1991 Created
|
|
*/
|
|
|
|
#include "xms.h"
|
|
|
|
#include <xmssvc.h>
|
|
#include <softpc.h>
|
|
|
|
void sas_enable_20_bit_wrapping(void);
|
|
void sas_disable_20_bit_wrapping(void);
|
|
BOOL sas_twenty_bit_wrapping_enabled(void);
|
|
|
|
BYTE * pHimemA20State = NULL;
|
|
|
|
|
|
/* xmsA20 - Handle A20 requests
|
|
*
|
|
*
|
|
* Entry - Client (AX) 0 - Disable A20
|
|
* 1 - Enable A20
|
|
* 2 - Query
|
|
*
|
|
* Exit
|
|
* SUCCESS
|
|
* Client (AX) = 1
|
|
* if on entry AX=2 Then
|
|
* Cleint (AX) =1 means was enabled
|
|
* Cleint (AX) =0 means was disabled
|
|
*
|
|
* FAILURE
|
|
* Client (AX) = 0
|
|
*/
|
|
|
|
VOID xmsA20 (VOID)
|
|
{
|
|
int reason;
|
|
|
|
reason = getAX();
|
|
|
|
setAX(1);
|
|
|
|
if (reason == 0)
|
|
xmsEnableA20Wrapping();
|
|
else if (reason == 1)
|
|
xmsDisableA20Wrapping();
|
|
else if (reason == 2) {
|
|
if (sas_twenty_bit_wrapping_enabled())
|
|
setAX(0);
|
|
setBL(0);
|
|
}
|
|
else
|
|
setAX(0);
|
|
}
|
|
// function to enable 1MB wrapping (turn off A20 line)
|
|
VOID xmsEnableA20Wrapping(VOID)
|
|
{
|
|
sas_enable_20_bit_wrapping();
|
|
if (pHimemA20State != NULL)
|
|
*pHimemA20State = 0;
|
|
|
|
#if 0 // this is not necessay because the intel space(pointed by
|
|
// HimemA20State) doesn't contain instruction
|
|
// doesn't contain instruction
|
|
#ifdef MIPS
|
|
Sim32FlushVDMPointer
|
|
(
|
|
(((ULONG)pHimemA20State >> 4) << 16) | ((ULONG)pHimemA20State & 0xF),
|
|
1,
|
|
pHimemA20State,
|
|
FALSE
|
|
);
|
|
|
|
#endif
|
|
#endif
|
|
|
|
}
|
|
|
|
// function to disable 1MB wrapping(turn on A20 line)
|
|
VOID xmsDisableA20Wrapping(VOID)
|
|
{
|
|
|
|
sas_disable_20_bit_wrapping();
|
|
if (pHimemA20State != NULL)
|
|
*pHimemA20State = 1;
|
|
#if 0 // this is not necessay because the intel space(pointed by
|
|
// HimemA20State) doesn't contain instruction
|
|
// doesn't contain instruction
|
|
#ifdef MIPS
|
|
Sim32FlushVDMPointer
|
|
(
|
|
(((ULONG)pHimemA20State >> 4) << 16) | ((ULONG)pHimemA20State & 0xF),
|
|
1,
|
|
pHimemA20State,
|
|
FALSE
|
|
);
|
|
|
|
#endif
|
|
#endif
|
|
|
|
}
|