On Mon, Jan 25, 2010 at 03:05:31PM -0800, H. Peter Anvin wrote:
quoted text
> On 01/25/2010 02:30 PM, Dmitry Torokhov wrote:
> >>
> >> We should never read from port 0x60 unless bit 1 in port 0x64 is set.
> >> Do we do that?
> > 
> > No, we don't read of OBF is 0. Incidentially 0xff has it set ;) so we do
> > try reading data port.
> > 
> 
> What do you do after reading the data port?  In the case of the A20
> code, we do dummy reads and loop until the data port drains (0xff of
> course means it never drains...)
> 

/*
 * i8042_flush() flushes all data that may be in the keyboard and mouse
 * buffers
 * of the i8042 down the toilet.
 */

static int i8042_flush(void)
{
        unsigned long flags;
        unsigned char data, str;
        int i = 0;

        spin_lock_irqsave(&i8042_lock, flags);

        while (((str = i8042_read_status()) & I8042_STR_OBF) && (i < I8042_BUFFER_SIZE)) {
                udelay(50);
                data = i8042_read_data();
                i++;
                dbg("%02x <- i8042 (flush, %s)", data,
                        str & I8042_STR_AUXDATA ? "aux" : "kbd");
        }

        spin_unlock_irqrestore(&i8042_lock, flags);

        return i;
}

...

static int i8042_controller_check(void)
{
        if (i8042_flush() == I8042_BUFFER_SIZE) {
                printk(KERN_ERR "i8042.c: No controller found.\n");
                return -ENODEV;
        }

        return 0;
}

-- 
Dmitry
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