i2c_gpio: Add methods to set or reset some bits in a register

This can be used to set or reset some bits in a register while
preserving the remaining state.

Signed-off-by: Chris Fiege <[email protected]>

usbsdmux/i2c_gpio.py

@@ -97,6 +97,20 @@ def output_values(self, values: int, bitmask: int = 0xFF):
             val = val | (values & bitmask)  # set bits set in values and bitmask
             self._write_register(self.register_outputPort, val)
 
+    def register_reset_bit(self, addr: int, bitmask: int):
+        """Resets the bits with '1' in <bitmask> in the register <addr>"""
+
+        val = self.read_register(addr)[0]
+        val = (val & ~bitmask) & 0xFF
+        self._write_register(addr, val)
+
+    def register_set_bit(self, addr: int, bitmask: int):
+        """Sets the bits with '1' in <bitmask> in the register <addr>"""
+
+        val = self.read_register(addr)[0]
+        val = (val | bitmask) & 0xFF
+        self._write_register(addr, val)
+
 
 class Pca9536(I2cGpio):
     """