input_merger: remove awkward initial_state setter, add notes

src/devices/machine/input_merger.cpp

@@ -14,8 +14,15 @@ Default initial input pin(s) state:
 - ALL_LOW: 0
 
 TODO:
-- call output handler at reset? eg. a NAND gate whose inputs are low at
-  power-on should output 1.
+- Change the strange initial input state, eg. right now it's all 1 for an AND
+  gate. All 0 for all devices would be more intuitive, but that would need a
+  config handler for setting the number of input pins since otherwise it can't
+  know if the state is active or not.
+- Call m_output_handler at reset, eg. a NOR gate whose inputs are low at power-on
+  should output 1 (to avoid surprises, this should be done after machine_reset).
+- Related to currently not calling m_output_handler at reset, if the hardware
+  1st value written equals the initial state, m_output_handler is not called,
+  eg. writing 1 to an AND gate pin when the default initial state is 1.
 
 ***************************************************************************/
 

src/devices/machine/input_merger.h

@@ -21,7 +21,6 @@ class input_merger_device : public device_t
 public:
 	// configuration
 	auto output_handler() { return m_output_handler.bind(); }
-	auto &initial_state(u32 val) { m_initval = val; return *this; } // initial input pin(s) state, be wary about the unused pins
 
 	// input lines
 	template <unsigned Bit> DECLARE_WRITE_LINE_MEMBER(in_w) { static_assert(Bit < 32, "invalid bit"); machine().scheduler().synchronize(timer_expired_delegate(FUNC(input_merger_device::update_state), this), (Bit << 1) | (state ? 1U : 0U)); }
@@ -48,7 +47,7 @@ protected:
 
 	devcb_write_line m_output_handler;
 
-	u32 m_initval;
+	u32 const m_initval;
 	u32 const m_xorval;
 	int const m_active;
 	u32 m_state;

src/mame/drivers/saitek_leonardo.cpp

@@ -372,7 +372,7 @@ void leo_state::leonardo(machine_config &config)
 	m_maincpu->in_p6_cb().set(FUNC(leo_state::p6_r));
 	m_maincpu->out_p6_cb().set(FUNC(leo_state::p6_w));
 
-	INPUT_MERGER_ANY_LOW(config, m_stb).initial_state(~u32(3));
+	INPUT_MERGER_ANY_LOW(config, m_stb);
 	m_stb->output_handler().set_inputline(m_maincpu, M6801_IS_LINE);
 
 	config.set_maximum_quantum(attotime::from_hz(6000));

src/mame/drivers/saitek_renaissance.cpp

@@ -361,7 +361,7 @@ void ren_state::ren(machine_config &config)
 	m_maincpu->in_p6_cb().set(FUNC(ren_state::p6_r));
 	m_maincpu->out_p6_cb().set(FUNC(ren_state::p6_w));
 
-	INPUT_MERGER_ANY_LOW(config, m_stb).initial_state(~u32(3));
+	INPUT_MERGER_ANY_LOW(config, m_stb);
 	m_stb->output_handler().set_inputline(m_maincpu, M6801_IS_LINE);
 
 	config.set_maximum_quantum(attotime::from_hz(6000));