Re: [hatari-devel] MIDI IRQ handling bug

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

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Hi Nicolas,

Would you have any objections to me pushing attached MIDI tracing change?


	- Eero

On 12.12.2021 16.09, Eero Tamminen wrote:
> Hi,
>
> On 12.12.2021 15.31, Nicolas Pomarède wrote:
> > Le 12/12/2021 à 14:23, Eero Tamminen a écrit :
> > > Current Hatari IRQ handling is buggy for MIDI. Midi_UnInit() disables 
> > > MIDI IRQ, but Midi_Init() does not enable it, only calling 
> > > Midi_Reset() does, which does not happen on MIDI device change.
> > >
> > > (Similarly to handling of RS232, SCC & printer devices, MIDI device 
> > > change at run-time does not trigger reset.)
> > >
> > > I tried calling Midi_Reset() directly from Midi_Init(), but that 
> > > freezes Hatari at startup (to somewhere in interrupt handling code).
> > >
> > > Attached patch seems to work, but I assume all the things done by 
> > > Midi_Reset() should not be done just on device change.
> > >
> > > Could you look into what's the correct fix?
> >
> > what scenario should I use to see this case and reproduce it ?
>
> Change MIDI device at run-time, e.g. from one that is not present on the 
> system, to a one that is.  In my case, I was doing that right after 
> boot, before starting the Atari MIDI application.
>
> Oddly SMF-Player seemed fairly uneffected, but most MIDI apps (e.g. 
> Sequencer One, Notator, Dr T's KCS) are completely broken by this bug. 
> Synth receives no MIDI events, or they come with huge delays (when one 
> moves mouse?).
>
>
> I was testing this with the PortMidi fix patch, but same should happen 
> with raw MIDI, as that bug is obvious just by looking at the code:
>
> * Midi_UnInit() disables IRQ set by Midi_Reset() at emulation start, and 
> calling Midi_Init() in Change_CopyChangedParamsToConfiguration() does 
> not re-enable it.
>
> * Only calling Midi_Reset() directly (= my patch), or indirectly (= 
> rebooting emulation) does that.
>
>
>      - Eero