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

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Message-ID: <d25d9c581f5b4f22c9b94761972aa0fe@artur-rojek.eu>
Date: Sun, 16 Nov 2025 13:34:46 +0100
From: Artur Rojek <contact@...ur-rojek.eu>
To: Florian Fuchs <fuchsfl@...il.com>
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 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.

> 
> btw, I have also a cdi file, that boots for me, although I heard there
> were issues on the NTSC-U devices, if helpful:
> https://github.com/foxdrodd/dreamcast-linux/releases/download/6.17.7/linux6177-joystick.cdi

Thanks for the cdi. I have no means to burn CDs anymore, so instead
I quickly built a small buildroot based rootfs, and booted it as
initramfs over serial line :-)

Cheers,
Artur

> 
> Thank you for your efforts,
> Florian