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Fixed bug 5161 - Autodetect controller mappings based on the Linux Gamepad Specification

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Jan Bujak

I wrote a new driver for my gamepad on Linux. I'd like SDL to support it out-of-box, as currently it just treats it as a generic joystick instead of a gamepad. From what I can see the only way to do that is to either 1) pick one of the already supported controllers' PID, VID and button layouts and have my driver send that (effectively lying that it's something else), or 2) submit a preconfigured, hardcoded mapping to SDL.

Both of those, in my opinion, are silly when we already have the Linux Gamepad Specification which standarizes this:

https://www.kernel.org/doc/html/v4.15/input/gamepad.html

Unfortunately SDL doesn't make use of it currently. So I've took it upon myself to add it; patch is in the attachments.

Basically what the patch does is that if SDL finds no built-it controller mappings for a given joystick it then asks the joystick backend to autodetect it, and that uses the relevant evdev bits to figure out which button/axis is which. (See the specs for more details.)

With this patch applied my own driver for my controller works out-of-box with SDL with no extra configuration and is correctly recognized as a gamepad; this is also going to be the case for any other driver which follows the Linux Gamepad Specification.
This commit is contained in:
Sam Lantinga 2020-05-29 13:37:21 -07:00
parent e2dbed9cfe
commit 345b4d7e14
18 changed files with 419 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

92
src/joystick/SDL_gamecontroller.c
View file

@ -1089,6 +1089,91 @@ static ControllerMapping_t *SDL_PrivateGetControllerMappingForNameAndGUID(const
return mapping;
}
static void SDL_PrivateAppendToMappingString(char *mapping_string,
size_t mapping_string_len,
const char *input_name,
SDL_InputMapping *mapping)
{
char buffer[16];
if (mapping->kind == EMappingKind_None) {
return;
}
SDL_strlcat(mapping_string, input_name, mapping_string_len);
SDL_strlcat(mapping_string, ":", mapping_string_len);
switch (mapping->kind) {
case EMappingKind_Button:
SDL_snprintf(buffer, sizeof(buffer), "b%i", mapping->target);
break;
case EMappingKind_Axis:
SDL_snprintf(buffer, sizeof(buffer), "a%i", mapping->target);
break;
case EMappingKind_Hat:
SDL_snprintf(buffer, sizeof(buffer), "h%i.%i", mapping->target >> 4, mapping->target & 0x0F);
break;
default:
SDL_assert(SDL_FALSE);
}
SDL_strlcat(mapping_string, buffer, mapping_string_len);
SDL_strlcat(mapping_string, ",", mapping_string_len);
}
static ControllerMapping_t *SDL_PrivateGenerateAutomaticControllerMapping(const char *name,
SDL_JoystickGUID guid,
SDL_GamepadMapping *raw_map)
{
SDL_bool existing;
char name_string[128];
char mapping[1024];
/* Remove any commas in the name */
SDL_strlcpy(name_string, name, sizeof(name_string));
{
char *spot;
for (spot = name_string; *spot; ++spot) {
if (*spot == ',') {
*spot = ' ';
}
}
}
SDL_snprintf(mapping, sizeof(mapping), "none,%s,", name_string);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "a", &raw_map->a);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "b", &raw_map->b);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "x", &raw_map->x);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "y", &raw_map->y);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "back", &raw_map->back);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "guide", &raw_map->guide);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "start", &raw_map->start);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "leftstick", &raw_map->leftstick);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "rightstick", &raw_map->rightstick);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "leftshoulder", &raw_map->leftshoulder);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "rightshoulder", &raw_map->rightshoulder);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "dpup", &raw_map->dpup);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "dpdown", &raw_map->dpdown);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "dpleft", &raw_map->dpleft);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "dpright", &raw_map->dpright);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "leftx", &raw_map->leftx);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "lefty", &raw_map->lefty);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "rightx", &raw_map->rightx);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "righty", &raw_map->righty);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "lefttrigger", &raw_map->lefttrigger);
SDL_PrivateAppendToMappingString(mapping, sizeof(mapping), "righttrigger", &raw_map->righttrigger);
/* Remove trailing comma */
{
int pos = (int)SDL_strlen(mapping) - 1;
if (pos >= 0) {
if (mapping[pos] == ',') {
mapping[pos] = '\0';
}
}
}
return SDL_PrivateAddMappingForGUID(guid, mapping,
&existing, SDL_CONTROLLER_MAPPING_PRIORITY_DEFAULT);
}
static ControllerMapping_t *SDL_PrivateGetControllerMapping(int device_index)
{
const char *name;
@ -1106,6 +1191,13 @@ static ControllerMapping_t *SDL_PrivateGetControllerMapping(int device_index)
name = SDL_JoystickNameForIndex(device_index);
guid = SDL_JoystickGetDeviceGUID(device_index);
mapping = SDL_PrivateGetControllerMappingForNameAndGUID(name, guid);
if (!mapping) {
SDL_GamepadMapping raw_map;
if (SDL_PrivateJoystickGetAutoGamepadMapping(device_index, &raw_map)) {
mapping = SDL_PrivateGenerateAutomaticControllerMapping(name, guid, &raw_map);
}
}
SDL_UnlockJoysticks();
return mapping;
}