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From: johnc@rtmvax.UUCP (John Connin)
Newsgroups: comp.os.minix
Subject: keyboard leds
Message-ID: <1997@rtmvax.UUCP>
Date: 19 Oct 88 15:12:32 GMT
Reply-To: johnc@rtmvax.UUCP (John Connin)
Organization: RTmVax Public Unix System, Orlando FL
Lines: 63





The function set_leds() within console.c does not work with my AT-clone.
More likely than not it will cause the 8042 keyboard controller to
reset its self.  The net effect is that either the typematic rate
will be reset (ie. I have it to 30 char / sec) or more importantly
will cause the system reset line to be set -- inturn causing the
system to reboot.

NB: increasing the delay parmeter 'LED_DELAY' is not enough.

The following code, which I believe corresponds to how the 8042 should
be programmed, solves the problem -- at least in my machine.  However,
beware that it does not contain any error recover mechanism.


#define KB_DATA         0x60    /* I/O port for keyboard data */
#define KB_STATUS       0x64    /* I/O port for keyboard status */
#define KB_FULL         0x02    /* keyboard full status mask */

#define LED_CODE        0xED	/* command to keyboard to set LEDs */
#define KB_ACK          0xFA    /* keyboard ack response  */


set_leds(leds)
int  leds;
{
    int  data_port, status_port;
    int  dummy;

    data_port   = KB_DATA;
    status_port = KB_STATUS;

    kb_ready(status_port);           /* wait for buffer empty  */

    port_out(data_port, LED_CODE);   /* prepare keyboard to accept LED values */

    kb_ack(data_port);               /* wait for ack response  */
    kb_ready(status_port);           /* wait for buffer empty  */

    port_out(data_port, leds & 0x0007);   /* give keyboard LED values */
    kb_ack(data_port);                    /* wait for ack response  */
}

kb_ready(port)
int port;
{
    int  status;

    do {  port_in(port,&status); }
    while (status & KB_FULL);
}

kb_ack(port)
int  port;
{
    int  response;

    do {  port_in(port,&response); }
    while (response != KB_ACK);
}