USB: Infinite length for FFB effects for wheel compatibility

Whoops. Turns out there wasn't some magic safety cutoff in modern wheels.
Rather, only some wheels were honoring SDL's infinite iteration count,
and others would abruptly stop after the effect's initial duration
(previously ten seconds) expired.

pcsx2/USB/usb-pad/usb-pad-sdl-ff.cpp

@@ -59,7 +59,19 @@ namespace usb_pad
 
 	void SDLFFDevice::CreateEffects(const std::string_view device)
 	{
-		constexpr u32 length = 10000; // 10 seconds since NFS games seem to not issue new commands while rotating.
+		// Most games appear to assume that requested forces will be applied indefinitely.
+		// Gran Turismo 4 uses a single indefinite constant force to center the wheel in menus, 
+		// and both GT4 and the NFS games have been observed using a single constant force 
+		// command over long, consistent turns.
+		// Not all wheels appear to honor SDL's "iteration count", meaning the effect will abruptly
+		// stop after the duration elapses even if it's still being actively updated. An infinite
+		// duration resolves this.
+		// 
+		// Known "Problem" wheels which require an infinite duration to avoid FFB cutouts:
+		//   - Moza series (R9 and R21 have been specifically observed)
+		//   - Simagic Alpha Mini
+		//   - Accuforce v2
+		constexpr u32 length = SDL_HAPTIC_INFINITY;
 
 		const unsigned int supported = SDL_HapticQuery(m_haptic);
 		if (supported & SDL_HAPTIC_CONSTANT)
@@ -187,13 +199,18 @@ namespace usb_pad
 				Console.Warning("SDL_HapticUpdateEffect() for constant failed: %s", SDL_GetError());
 		}
 
-		// Always 'run' the constant force effect, even when already running. This
-		// mitigates FFB timeout issues experienced by some modern direct-drive
-		// wheels, such as Moza R5, R9, etc...
-		if (SDL_HapticRunEffect(m_haptic, m_constant_effect_id, SDL_HAPTIC_INFINITY) == 0)
-			m_constant_effect_running = true;
-		else
-			Console.Error("SDL_HapticRunEffect() for constant failed: %s", SDL_GetError());
+		// Avoid re-running already-running effects. Some (not all) wheels will briefly drop the
+		// force if it is re-run, resulting in a "jackhammering" or "cobblestone" feeling.
+		// 
+		// Known problem wheels:
+		// Accuforce V2
+		if (!m_constant_effect_running)
+		{
+			if (SDL_HapticRunEffect(m_haptic, m_constant_effect_id, SDL_HAPTIC_INFINITY) == 0)
+				m_constant_effect_running = true;
+			else
+				Console.Error("SDL_HapticRunEffect() for constant failed: %s", SDL_GetError());
+		}
 	}
 
 	template <typename T>