Unfortunately the fix didn't work in my case.

[AssisrMatheus]

I'm willing to help extend the solution to find the fix.

I've just built sdl3, installed it locally then build and run the c file, with the following output:

$ ./get-controller-config
Joystick 0: Steam Deck
        To use this controller in Silksong, set the following environment variable when running the game:

        SDL_GAMECONTROLLERCONFIG='03000000de2800000512000000036800,Steam Deck Controller,a:b0,b:b1,back:b4,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,misc1:b11,paddle1:b12,paddle2:b13,paddle3:b14,paddle4:b15,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,platform:Linux,'

        For example, Steam launch options would be:

        SDL_GAMECONTROLLERCONFIG='03000000de2800000512000000036800,Steam Deck Controller,a:b0,b:b1,back:b4,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,misc1:b11,paddle1:b12,paddle2:b13,paddle3:b14,paddle4:b15,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,platform:Linux,' %command%

Joystick 1: 8BitDo Ultimate 2 Wireless Controller for PC
        To use this controller in Silksong, set the following environment variable when running the game:

        SDL_GAMECONTROLLERCONFIG='03000000c82d00000b31000014016800,*,a:b0,b:b1,back:b4,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,crc:cdb5,platform:Linux,'

        For example, Steam launch options would be:

        SDL_GAMECONTROLLERCONFIG='03000000c82d00000b31000014016800,*,a:b0,b:b1,back:b4,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,crc:cdb5,platform:Linux,' %command%

But unfortunately, after setting that as steam launch, the controller doesn't work at all regardless. Tried enabling/disabling steam input with no change as well (and yes, NativeInput is set to 0 too :( )

I saw the example code in the repo and that it has the controller name in it, while this output has *. I also replaced * with 8BitDo Ultimate 2 Wireless Controller for PC which is my controller's name, but no success.

---

Asking AI also replied with this, which I tried, re-built, but also no success, but posting here just in case:
Looking at the C code and the output, I can identify the problem. The code has a critical logic error in how it modifies the GUID string in the mapping.

The Problem

The code attempts to zero out CRC bytes by modifying the mapping string directly, but this approach has several issues:

1. Wrong target: The code is trying to modify bytes 2-4 of the mapping string (which is the entire gamepad configuration string like "03000000c82d00000b31000014016800,*,a:b0,b:b1..."), not the GUID portion within it.
2. String immutability: In SDL3, SDL_GetGamepadMappingForGUID() now returns a const char* (not char*) as part of the SDL_GetStringRule changes. This means the returned string should not be modified directly.
3. Invalid approach: The loop for (size_t guid_byte = 2; guid_byte < 4; guid_byte++) is modifying positions 4-7 of the mapping string (which would be part of "0300..." at the start), but this isn't correctly targeting the GUID bytes.

The Fix

The code needs to:

1. Extract the GUID portion from the mapping string (the first part before the comma)
2. Zero out bytes 4-7 (indices 4-7 in the hex string, representing GUID bytes 2-3)
3. Reconstruct the mapping string with the modified GUID

Here's the corrected version:

char* mapping = SDL_GetGamepadMappingForGUID(guid);
if (mapping == NULL) {
    fprintf(stderr, "\tNo mapping available for this controller\n");
    SDL_CloseJoystick(joystick);
    continue;
}

// Find the first comma (end of GUID portion)
char* comma = strchr(mapping, ',');
if (comma == NULL) {
    fprintf(stderr, "\tInvalid mapping format\n");
    SDL_free(mapping);
    SDL_CloseJoystick(joystick);
    continue;
}

// Create a modified mapping string with zeroed CRC bytes
size_t guid_len = comma - mapping;
char* modified_mapping = malloc(strlen(mapping) + 1);
strcpy(modified_mapping, mapping);

// Zero out bytes at positions 4-7 (GUID bytes 2-3, which are the CRC)
modified_mapping[^4] = '0';
modified_mapping[^5] = '0';
modified_mapping[^6] = '0';
modified_mapping[^7] = '0';

printf("\tTo use this controller in Silksong, set the following environment variable when running the game:\n\n");
printf("\tSDL_GAMECONTROLLERCONFIG='%s'\n\n", modified_mapping);
printf("\tFor example, Steam launch options would be:\n\n");
printf("\tSDL_GAMECONTROLLERCONFIG='%s' %%command%%\n\n", modified_mapping);

free(modified_mapping);
SDL_CloseJoystick(joystick);
SDL_free(mapping);

The original code was modifying the wrong positions in the string, which is why the generated mapping strings weren't working for Silksong.

[AssisrMatheus]

Would it be possible to make a mod that fixes this? (not asking you to do it, just whether this is something that a mod could inject)

[NelsonAPenn]

Hi,

The AI answer is not accurate; SDL_GetGamepadMappingForGUID does not return a const char*. I can see in the output that the CRC portion of the GUID has been successfully zeroed. So that much is working.

A couple questions:

• Just making sure, you are using the last line only for the Steam launch options?
• What was the behavior before performing the steps presented in this repository? Was it the same strange behavior I cited with the trigger buttons not working, or was the controller just completely ignored? For me, even when the controller config was not successfully detected I could still do basic movement and button presses (just trigger buttons acted strangely)
• Is steam input on for the game? It may be by default for Steam Decks. You could try turning that off

This is a different model of controller than the one I tested it with; though I think this approach should work for any controller supported in SDL3 but not in SDL2, I have not tested this assumption with other models.

[NelsonAPenn]

It also appears that SDL3 doesn't have a controller config for your specific model of controller (which this fix does rely on).
When SDL can't find a matching controller config in the database, it will make an educated guess as to what the mapping should be-- that's why the controller name is *.

I still recommend trying some of the other troubleshooting steps (such as disabling Steam Input if it is on). SDL's educated guess at a mapping may work for you. I would think you should get at least some response from the controller.

However, it is still possible that the fix doesn't work because of the mapping not being in SDL's database, at which point I wouldn't be able to do much to help.

[AssisrMatheus]

Hi,

The AI answer is not accurate; SDL_GetGamepadMappingForGUID does not return a const char*. I can see in the output that the CRC portion of the GUID has been successfully zeroed. So that much is working.

A couple questions:

* Just making sure, you are using the last line only for the Steam launch options?

* What was the behavior before performing the steps presented in this repository? Was it the same strange behavior I cited with the trigger buttons not working, or was the controller just completely ignored? For me, even when the controller config was not successfully detected I could still do basic movement and button presses (just trigger buttons acted strangely)

* Is steam input on for the game? It may be by default for Steam Decks. You could try turning that off

This is a different model of controller than the one I tested it with; though I think this approach should work for any controller supported in SDL3 but not in SDL2, I have not tested this assumption with other models.

Yep, sorry for the poorly written issue, it was late night and my brain was fried trying to solve the issue lol.

* Just making sure, you are using the last line only for the Steam launch options?

Yes, with %command%

* What was the behavior before performing the steps presented in this repository? Was it the same strange behavior I cited with the trigger buttons not working, or was the controller just completely ignored? For me, even when the controller config was not successfully detected I could still do basic movement and button presses (just trigger buttons acted strangely)

That's it, the exact issue with the triggers. But then when I turn steam input off + NativeInput=0 and everything, and try setting the ENV for sdl, unfortunately the controller didn't detect at all

* Is steam input on for the game? It may be by default for Steam Decks. You could try turning that off

No, tried with it off, on or on "default" option (which i think turns on for "Generic" controllers anyway).

However, it is still possible that the fix doesn't work because of the mapping not being in SDL's database, at which point I wouldn't be able to do much to help.

That's unfortunate, I saw the SDL database but really couldn't find my controller there so maybe that's the case, I wonder why it didn't work with the other mappings for similar controllers (like the 2C Ultimate), as I assume it has similar internals/firmware. Oh well...

I know it's not your fault, but thought maybe your knowledge could add to this. Well, thanks for your work!

[NelsonAPenn]

Hmm, I still think it's weird you aren't getting anything after using the launch options, especially if you were seeing the same behavior I described beforehand. I probably wouldn't give up just yet, there's some more troubleshooting you can try. Do the steam deck controller's inputs still work after setting the env var? I would maybe try compiling [SDL jstest](https://github.com/Grumbel/sdl-jstest) and seeing how the controller behaves. Do the controller inputs show up? And do they continue to show up after setting the env var?

[AssisrMatheus]

Hmm, I still think it's weird you aren't getting anything after using the launch options, especially if you were seeing the same behavior I described beforehand.
I probably wouldn't give up just yet, there's some more troubleshooting you can try.
Do the steam deck controller's inputs still work after setting the env var?
I would maybe try compiling SDL jstest and seeing how the controller behaves. Do the controller inputs show up? And do they continue to show up after setting the env var?

video.webm

5 is the right trigger, and 3 is the left trigger here and it seems to register as expected

So this is what I got. Apparently SDL2 do see the correct controller (with a different name):

Joystick Name:     '8BitDo Ultimate 2 Wireless Controller'
Joystick GUID:     0300f6b6c82d00000b31000014010000
Joystick Number:    0
Number of Axes:     6
Number of Buttons: 11
Number of Hats:     1
Number of Balls:    0
GameControllerConfig:
  Name:    '8BitDo Ultimate 2 Wireless Controller'
  Mapping: '0300f6b6c82d00000b31000014010000,8BitDo Ultimate 2 Wireless Controller,a:b0,b:b1,x:b2,y:b3,back:b6,guide:b8,start:b7,leftstick:b9,rightstick:b10,leftshoulder:b4,rightshoulder:b5,dpup:h0.1,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,leftx:a0,lefty:a1,rightx:a3,righty:a4,lefttrigger:a2,righttrigger:a5,crc:b6f6,platform:Linux'

(You can see it became joystick 0 here compared to the video, after a while, steam deck's own controller disappeared)

Though, after I set SDL_GAMECONTROLLERCONFIG, it stops being recognized.

This is using the output from ./get-controller-config:

(deck@steamdeck build)$ export SDL_GAMECONTROLLERCONFIG='03000000c82d00000b31000014016800,*,a:b0,b:b1,back:b4,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b5,leftshoulder:b9,leftstick:b7,lefttrigger:a4,leftx:a0,lefty:a1,rightshoulder:b10,rightstick:b8,righttrigger:a5,rightx:a2,righty:a3,start:b6,x:b2,y:b3,crc:cdb5,platform:Linux,'
(deck@steamdeck build)$ ./sdl2-jstest -l
No joysticks were found
(deck@steamdeck build)$ ./sdl2-jstest -t 1
Unable to open joystick 1
(deck@steamdeck build)$ ./sdl2-jstest -t 0
Unable to open joystick 0

This is after building my own version of it using the values from ./sdl2-jstest:

(130)(deck@steamdeck build)$ export SDL_GAMECONTROLLERCONFIG='0300f6b6c82d00000b31000014010000,8BitDo Ultimate 2 Wireless Controller,a:b0,b:b1,x:b2,y:b3,back:b6,guide:b8,start:b7,leftstick:b9,rightstick:b10,leftshoulder:b4,rightshoulder:b5,dpup:h0.1,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,leftx:a0,lefty:a1,rightx:a3,righty:a4,lefttrigger:a2,righttrigger:a5,crc:b6f6,platform:Linux'
(deck@steamdeck build)$ ./sdl2-jstest -l
No joysticks were found

Though, using ./sdl2-jstest mappings as launch options, the controller works in game, but the same original problem occurs

[NelsonAPenn]

Gotcha, so one mystery that needs to be solved is:

Why is the specific model of controller recognized in sdl2-jstest but is missing from SDL3 controller DB?

I'll probably have to do some digging through git history and stuff to figure this out.

Regarding the behavior, it sounds like when the original problem occurs, the controller config is not picked up on by Silksong. When the game doesn't pick up on any controller inputs it likely picked up on the configuration but there is still something incompatible with it.

Could you try these launch options with Silksong? This is the sdl2-jstest config you posted with the CRC in the GUID zeroed out. The same thing my program would be doing except for the fact that it doesn't seem to have the configuration for your exact model of controller.

SDL_GAMECONTROLLERCONFIG='03000000c82d00000b31000014010000,8BitDo Ultimate 2 Wireless Controller,a:b0,b:b1,x:b2,y:b3,back:b6,guide:b8,start:b7,leftstick:b9,rightstick:b10,leftshoulder:b4,rightshoulder:b5,dpup:h0.1,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,leftx:a0,lefty:a1,rightx:a3,righty:a4,lefttrigger:a2,righttrigger:a5,crc:b6f6,platform:Linux' %command%

[NelsonAPenn]

Also I notice when I did this for my controller, there wasn't a CRC field in the configuration. Please try this too (same thing but that option removed). Maybe that is causing the incompatibility.

SDL_GAMECONTROLLERCONFIG='03000000c82d00000b31000014010000,8BitDo Ultimate 2 Wireless Controller,a:b0,b:b1,x:b2,y:b3,back:b6,guide:b8,start:b7,leftstick:b9,rightstick:b10,leftshoulder:b4,rightshoulder:b5,dpup:h0.1,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,leftx:a0,lefty:a1,rightx:a3,righty:a4,lefttrigger:a2,righttrigger:a5,platform:Linux' %command%