Commit 5ae0dd4b5223a2002950b831caeb652a44340517
2021-07-24T17:44:35
joystick: Split out Linux opening code for reuse by querying code. This prevents an assertion whem LINUX_JoystickGetGamepadMapping tried to open the stick temporarily and messed with global state by doing so. Now the global state is only set in LINUX_JoystickOpen, but the common code is shared by both interfaces. Fixes #4198.
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diff --git a/src/joystick/linux/SDL_sysjoystick.c b/src/joystick/linux/SDL_sysjoystick.c
index f0c2d5c..3e267e3 100644
--- a/src/joystick/linux/SDL_sysjoystick.c
+++ b/src/joystick/linux/SDL_sysjoystick.c
@@ -965,26 +965,14 @@ ConfigJoystick(SDL_Joystick *joystick, int fd)
}
-/* Function to open a joystick for use.
- The joystick to open is specified by the device index.
- This should fill the nbuttons and naxes fields of the joystick structure.
- It returns 0, or -1 if there is an error.
- */
+/* This is used to do the heavy lifting for LINUX_JoystickOpen and
+ also LINUX_JoystickGetGamepadMapping, so we can query the hardware
+ without adding an opened SDL_Joystick object to the system.
+ This expects `joystick->hwdata` to be allocated and will not free it
+ on error. Returns -1 on error, 0 on success. */
static int
-LINUX_JoystickOpen(SDL_Joystick *joystick, int device_index)
+PrepareJoystickHwdata(SDL_Joystick *joystick, SDL_joylist_item *item)
{
- SDL_joylist_item *item = JoystickByDevIndex(device_index);
-
- if (item == NULL) {
- return SDL_SetError("No such device");
- }
-
- joystick->instance_id = item->device_instance;
- joystick->hwdata = (struct joystick_hwdata *)
- SDL_calloc(1, sizeof(*joystick->hwdata));
- if (joystick->hwdata == NULL) {
- return SDL_OutOfMemory();
- }
joystick->hwdata->item = item;
joystick->hwdata->guid = item->guid;
joystick->hwdata->effect.id = -1;
@@ -997,18 +985,14 @@ LINUX_JoystickOpen(SDL_Joystick *joystick, int device_index)
&joystick->naxes,
&joystick->nhats);
} else {
- int fd = open(item->path, O_RDWR, 0);
+ const int fd = open(item->path, O_RDWR, 0);
if (fd < 0) {
- SDL_free(joystick->hwdata);
- joystick->hwdata = NULL;
return SDL_SetError("Unable to open %s", item->path);
}
joystick->hwdata->fd = fd;
joystick->hwdata->fname = SDL_strdup(item->path);
if (joystick->hwdata->fname == NULL) {
- SDL_free(joystick->hwdata);
- joystick->hwdata = NULL;
close(fd);
return SDL_OutOfMemory();
}
@@ -1019,6 +1003,35 @@ LINUX_JoystickOpen(SDL_Joystick *joystick, int device_index)
/* Get the number of buttons and axes on the joystick */
ConfigJoystick(joystick, fd);
}
+}
+
+
+/* Function to open a joystick for use.
+ The joystick to open is specified by the device index.
+ This should fill the nbuttons and naxes fields of the joystick structure.
+ It returns 0, or -1 if there is an error.
+ */
+static int
+LINUX_JoystickOpen(SDL_Joystick *joystick, int device_index)
+{
+ SDL_joylist_item *item = JoystickByDevIndex(device_index);
+
+ if (item == NULL) {
+ return SDL_SetError("No such device");
+ }
+
+ joystick->instance_id = item->device_instance;
+ joystick->hwdata = (struct joystick_hwdata *)
+ SDL_calloc(1, sizeof(*joystick->hwdata));
+ if (joystick->hwdata == NULL) {
+ return SDL_OutOfMemory();
+ }
+
+ if (PrepareJoystickHwdata(joystick, item) == -1) {
+ SDL_free(joystick->hwdata);
+ joystick->hwdata = NULL;
+ return -1; /* SDL_SetError will already have been called */
+ }
SDL_assert(item->hwdata == NULL);
item->hwdata = joystick->hwdata;
@@ -1026,7 +1039,7 @@ LINUX_JoystickOpen(SDL_Joystick *joystick, int device_index)
/* mark joystick as fresh and ready */
joystick->hwdata->fresh = SDL_TRUE;
- return (0);
+ return 0;
}
static int
@@ -1417,18 +1430,32 @@ LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMapping *out)
return SDL_TRUE;
}
+ /* We temporarily open the device to check how it's configured. Make
+ a fake SDL_Joystick object to do so. */
joystick = (SDL_Joystick *) SDL_calloc(sizeof(*joystick), 1);
if (joystick == NULL) {
SDL_OutOfMemory();
return SDL_FALSE;
}
- /* We temporarily open the device to check how it's configured. */
- if (LINUX_JoystickOpen(joystick, device_index) < 0) {
+ joystick->hwdata = (struct joystick_hwdata *)
+ SDL_calloc(1, sizeof(*joystick->hwdata));
+ if (joystick->hwdata == NULL) {
SDL_free(joystick);
+ SDL_OutOfMemory();
return SDL_FALSE;
}
+ if (PrepareJoystickHwdata(joystick, item) == -1) {
+ SDL_free(joystick->hwdata);
+ SDL_free(joystick);
+ return SDL_FALSE; /* SDL_SetError will already have been called */
+ }
+
+ /* don't assign `item->hwdata` so it's not in any global state. */
+
+ /* it is now safe to call LINUX_JoystickClose on this fake joystick. */
+
if (!joystick->hwdata->has_key[BTN_GAMEPAD]) {
/* Not a gamepad according to the specs. */
LINUX_JoystickClose(joystick);