Re: [Qemu-devel] Regression: more 0.12 regression (SeaBIOS related?)

[Roy Tam <roytam@gmail.com>]

2010/3/12 Kevin O'Connor <kevin@koconnor.net>:
> On Thu, Mar 11, 2010 at 03:42:28PM +0800, Roy Tam wrote:
>> Sorry I can't find documentation on this usage. But instead I have
>> lots of old programs written with this usage.
>> Using undocumented features from BIOS/DOS is very usual in that time.
>
> Can you confirm these other programs fail in the same way (no keyboard
> input, and "ps2 irq but no data." messages in log when using
> bios.bin-0.5.1-debug-20100228)?
>
>> > It's broken because it causes key presses to be lost and corrupted.
>> > The ps2 port hardware just doesn't work the way that software is
>> > trying to use it.
>> >
>>
>> You said that "it causes key presses to be lost and corrupted" but I
>> haven't heard any complain about this.
>> Real BIOSes (Award BIOS, AMI BIOS, Phoenix BIOS) handle this usage
>> very well and no key press are lost or corrupted.
>
> Under qemu-0.11 normal typing lead to lots of keyboard errors for me.
> It's possible real hardware would be less susceptible to this error,
> but there is nothing that a BIOS inside qemu can do to stop the
> corruption.
>
>> Any key press should generate 4 IRQs, for example when I press [Tab]
>> key, it should have IRQs like this:
>> ps2: data f (status=1d)
>> ps2: data f (status=1c)
>> ps2: data 8f (status=1d)
>> ps2: data 8f (status=1c)
>
> There is one irq on key press and one irq on key release.  Your
> debugging output is in a loop and you're reporting the same event
> twice.
>
>> The following patch help people to see irq status and data change:
>
> The current SeaBIOS flow is effectively:
>
>        // Read ps2 port status
>        u8 status = inb(PORT_PS2_STATUS);
>        if (!(status & I8042_STR_OBF))
>            // No event in queue - nothing can be dequeued.
>            return;
>        // Event in queue - dequeue it
>        u8 data = inb(PORT_PS2_DATA);
>        // Process the event.
>        process_ps2byte(status, data);
>
> Your debugging patch is not correct becuase it performs the event
> dequeue before the check to see if there is an event in the queue.
>

I don't care about it. As mentioned in OSDEV wiki (
http://wiki.osdev.org/PS2_Keyboard ):
Note that if you repeatedly read the port 0x60 without waiting for
another IRQ, you'll read the same byte again. That's the 'normal'
behaviour of keyboard controller, [...]