Re: [Qemu-devel] [PATCH 11/22] i8259: Update IRQ state after reset

[Blue Swirl]

On Sun, Oct 2, 2011 at 7:08 PM, Avi Kivity <address@hidden> wrote:
>> > phase 1: reset internal state (-> move all outputs to reset
>> > values), don't
>> > sample inputs yet
>>
>> This solves the problem of old state accidentally interfering with
>> reset state.
>>
>> > phase 2: allow sampling inputs
>>
>> This could lead to incorrect state for complex networks. It would
>> still be better than what we have now.
>>
>
> Can you give an example?  Can be theoretical, doesn't have to refer to real 
> hardware.

For example, outputs A and B should both be driven high by reset. They
are connected to a XNOR gate, whose output is fed to edge triggered
device. The device should not see any edges outside of the reset
cycle, during reset cycle they are ignored.