91 lines
2.2 KiB
C
91 lines
2.2 KiB
C
#include "realmode.h"
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#include "timer.h"
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#include "latch.h"
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#include "bios.h"
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#define K_RDWR 0x60 /* keyboard data & cmds (read/write) */
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#define K_STATUS 0x64 /* keyboard status */
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#define K_CMD 0x64 /* keybd ctlr command (write-only) */
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#define K_OBUF_FUL 0x01 /* output buffer full */
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#define K_IBUF_FUL 0x02 /* input buffer full */
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#define KC_CMD_WIN 0xd0 /* read output port */
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#define KC_CMD_WOUT 0xd1 /* write output port */
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#define KB_SET_A20 0xdf /* enable A20,
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enable output buffer full interrupt
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enable data line
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disable clock line */
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#define KB_UNSET_A20 0xdd /* enable A20,
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enable output buffer full interrupt
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enable data line
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disable clock line */
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enum { Disable_A20 = 0x2400, Enable_A20 = 0x2401, Query_A20_Status = 0x2402,
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Query_A20_Support = 0x2403 };
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#define CF ( 1 << 0 )
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#ifndef IBM_L40
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static void empty_8042 ( void )
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{
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unsigned long time;
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char st;
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time = currticks() + TICKS_PER_SEC; /* max wait of 1 second */
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while ((((st = inb(K_CMD)) & K_OBUF_FUL) ||
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(st & K_IBUF_FUL)) &&
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currticks() < time)
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inb(K_RDWR);
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}
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#endif /* IBM_L40 */
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/*
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* Gate A20 for high memory
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*
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* Note that this function gets called as part of the return path from
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* librm's real_call, which is used to make the int15 call if librm is
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* being used. To avoid an infinite recursion, we make gateA20_set
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* return immediately if it is already part of the call stack.
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*/
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void gateA20_set ( void ) {
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static char reentry_guard = 0;
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uint16_t flags, status;
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if ( reentry_guard )
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return;
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reentry_guard = 1;
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REAL_EXEC ( rm_enableA20,
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"sti\n\t"
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"stc\n\t"
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"int $0x15\n\t"
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"pushfw\n\t"
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"popw %%bx\n\t"
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"cli\n\t",
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2,
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OUT_CONSTRAINTS ( "=a" ( status ), "=b" ( flags ) ),
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IN_CONSTRAINTS ( "a" ( Enable_A20 ) ),
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CLOBBER ( "ecx", "edx", "ebp", "esi", "edi" ) );
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if ( ( flags & CF ) ||
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( ( status >> 8 ) & 0xff ) ) {
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/* INT 15 method failed, try alternatives */
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#ifdef IBM_L40
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outb(0x2, 0x92);
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#else /* IBM_L40 */
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empty_8042();
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outb(KC_CMD_WOUT, K_CMD);
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empty_8042();
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outb(KB_SET_A20, K_RDWR);
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empty_8042();
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#endif /* IBM_L40 */
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}
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reentry_guard = 0;
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}
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void gateA20_unset ( void ) {
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/* Not currently implemented */
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}
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