Re: [Qemu-devel] [PATCH v4 5/5] i8259: fix dynamically masking slave IRQs with IMR register

[Jan Kiszka]

On 2012-09-05 06:33, Matthew Ogilvie wrote:
> According to later discussion, the main issue is actually the input
> IRQ behavior on a high to low transition; hence the following fixes
> both the test program and the Microport UNIX problem:
> 
> diff --git a/hw/i8259.c b/hw/i8259.c
> index 6587666..c011787 100644
> --- a/hw/i8259.c
> +++ b/hw/i8259.c
> @@ -143,22 +143,23 @@ static void pic_set_irq(void *opaque, int irq, int 
> level)
>      if (s->elcr & mask) {
>          /* level triggered */
>          if (level) {
>              s->irr |= mask;
>              s->last_irr |= mask;
>          } else {
>              s->irr &= ~mask;
>              s->last_irr &= ~mask;
>          }
>      } else {
>          /* edge triggered */
>          if (level) {
>              if ((s->last_irr & mask) == 0) {
>                  s->irr |= mask;
>              }
>              s->last_irr |= mask;
>          } else {
> +            s->irr &= ~mask;
>              s->last_irr &= ~mask;
>          }
>      }
>      pic_update_irq(s);
>  }
>  
> 
> Perhaps it would be worth it to swap around the "if"s a little bit
> to avoid the (!level) duplication, and clarify that the only difference
> is in the low to high transition?

Yes, refactoring would be welcome. But I would suggest to do this in two
patches, leaving the above change (+ changelog that explains the reason)
in its current clarity.

Hurray, no vmstate subsections needed! :)

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux