linux-kernel - Re: [PATCH] sh: maple: fix empty port handling

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Message-ID: <aRoPeNu7UZog0srr@lithos>
Date: Sun, 16 Nov 2025 18:52:56 +0100
From: Florian Fuchs <fuchsfl@...il.com>
To: Artur Rojek <contact@...ur-rojek.eu>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>
Subject: Re: [PATCH] sh: maple: fix empty port handling

On 16 Nov 13:34, Artur Rojek wrote:
> On 2025-11-12 23:46, Florian Fuchs wrote:
> > Hi Artur,
> > thank you so much for fixing the DC boot on linux again!
> > Adrian, thank you for looking at it!
> > 
> > On 12 Nov 22:46, Artur Rojek wrote:
> > > thanks for the patch! Can this be tested with just regular
> > > controllers?
> > 
> > Yes, indeed you can test it with the controller, when you compile with
> > joystick support, like:
> > 
> > 	CONFIG_MAPLE=y
> > 	CONFIG_INPUT=y
> > 	CONFIG_INPUT_JOYDEV=y
> > 	CONFIG_INPUT_EVDEV=y
> > 	CONFIG_INPUT_JOYSTICK=y
> > 	CONFIG_JOYSTICK_MAPLE=y
> > 
> > You should not put a VMU in though, as thats currently broken (I have a
> > patch ready).
> > 
> > Then you can directly read from the evdev and listen for the button
> > presses:
> > 	bash-5.3# cat /dev/input/event2 | xxd
> > 
> > You need to press a button for 20-30 times, as it seems to buffer the
> > events and outputs it in batches.
> > 
> > Then, you should see the following outputs for the buttons:
> > 
> > Button A:
> > 	00000000: 7800 0000 94c3 0d00 0100 3001 0000 0000  x.........0.....
> > Button B:
> > 	000001e0: 7800 0000 94c3 0d00 0100 3101 0100 0000  x.........1....
> > Button X:
> > 	000003b0: 7800 0000 94c3 0d00 0100 3301 0100 0000  x.........3.....
> > Button Y:
> > 	00000900: 7800 0000 94c3 0d00 0100 3401 0100 0000  x.........4.....
> > 
> > The Joystick should be detected like this:
> > 	/ # dmesg|grep maple
> > 	maple: bus core now registered
> > 	maple (null): detected Dreamcast Controller: function 0x1: at (2, 0)
> > 	maple (null): no driver found
> > 	input: Dreamcast Controller as /devices/maple/2:00.1/input/input2
> > 
> > Another indicator is the dmesg log for empty ports:
> > 	maple (null): no devices to port 3
> > 
> > These messages were previously not there, as the empty ports were never
> > detected.
> 
> Hey Florian,
> 
> Before applying this patch, no input on a maple port is being registered
> until all 4 maple ports are populated (in my case by four controllers).
> Once all 4 are plugged in, I can register input on either of them by
> cat-ing their respective char devs.
> 
> After applying the patch, I confirm that input can be read immediately
> for the present devices, even if the other ports are unpopulated.
> 
> However, this patch also breaks hotplug on maple ports - I can no longer
> plug in additional controllers at runtime and have them show up.
> 
> I think we need to hold off on this patch until the hotplug issue is
> addressed.
> 

Thank you for taking the time to test it! And sorry for the obvious issue,
I think my testing was wrong as I just removed and plugged in an already
registered device, and missed it with a new one.

Regards,
Florian