Re: [PATCH] sh: maple: fix empty port handling

[Artur Rojek]

On 2025-11-12 22:31, John Paul Adrian Glaubitz wrote:
> Hi Florian.
>
> On Wed, 2025-11-12 at 20:04 +0100, Florian Fuchs wrote:
> > Handle timeout response from empty ports of the maple bus to prevent a
> > stuck maple_sentq and a blocked maple bus.
> >
> > When only some ports are used, e.g. if only keyboard is connected and 
> > the
> > other ports are empty, the device tends to timeout and return 0xff for
> > the empty port. This needs to be handled, just like the
> > MAPLE_RESPONSE_NONE response, to detect empty ports and to have usable
> > peripherals, if not all of the ports are utilized. Previously, an 
> > empty
> > port resulted in a never cleared maple_sentq which totally blocked the
> > maple bus to be used.
> >
> > Signed-off-by: Florian Fuchs <fuchsfl@xxxxxxxxx>
> > ---
> > Note: This patch was tested on real Sega Dreamcast hardware and 
> > resulted
> > in a usable keyboard, even when only 1 or 2 ports where populated. The
> > hot-plugging of the keyboard does also work fine.
> >
> > The description of the timeout response can be obtained on the bottom 
> > of
> > of the page: https://mc.pp.se/dc/maplebus.html: "If no response is
> > received before the timeout, a word with all bits set (FFFFFFFF) is
> > written at the Result address."
> >
> >  drivers/sh/maple/maple.c | 1 +
> >  include/linux/maple.h    | 3 ++-
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/sh/maple/maple.c b/drivers/sh/maple/maple.c
> > index 6dc0549f7900..3d6c716cfc98 100644
> > --- a/drivers/sh/maple/maple.c
> > +++ b/drivers/sh/maple/maple.c
> > @@ -649,6 +649,7 @@ static void maple_dma_handler(struct work_struct 
> > *work)
> >  			list_del_init(&mq->list);
> >  			switch (code) {
> >  			case MAPLE_RESPONSE_NONE:
> > +			case MAPLE_RESPONSE_TIMEOUT:
> >  				maple_response_none(mdev);
> >  				break;
> >
> > diff --git a/include/linux/maple.h b/include/linux/maple.h
> > index 3be4e567473c..4ae3cc6678a8 100644
> > --- a/include/linux/maple.h
> > +++ b/include/linux/maple.h
> > @@ -27,7 +27,8 @@ enum maple_code {
> >  	MAPLE_COMMAND_BWRITE,
> >  	MAPLE_COMMAND_BSYNC,
> >  	MAPLE_COMMAND_SETCOND,
> > -	MAPLE_COMMAND_MICCONTROL
> > +	MAPLE_COMMAND_MICCONTROL,
> > +	MAPLE_RESPONSE_TIMEOUT = 255
> >  };
> >
> >  enum maple_file_errors {
> >
> > base-commit: 24172e0d79900908cf5ebf366600616d29c9b417
>
> Thanks for your patch! I'll try to get it reviewed in the weekend.
>
> In the meantime, I'll like to add Artur Rojek who did some work for 
> Linux on the
> Dreamcast as well if I remember correctly. Maybe he could test your 
> patch as I
> currently don't have my Dreamcast set up for testing.

Hi Adrian,
I indeed did some minor work to restore Dreamcast support in Linux. Will
give this patch a try once I find some free time.

Florian,
thanks for the patch! Can this be tested with just regular controllers?
I don't own a Dreamcast keyboard.

Cheers,
Artur


> Adrian