Add /dev/i2c driver

i2c_interfaces.py

@@ -27,6 +27,36 @@ class I2CInterface:
         pass
 
 
+class DevI2CInterface(I2CInterface):
+    def __init__(self, bus) -> None:
+        super().__init__()
+        from smbus import SMBus, i2c_msg
+        self.bus = SMBus(bus)
+        self.msg = i2c_msg
+
+    def read(self, addr: int, length: int) -> bytes:
+        m = self.msg.read(addr, length)
+        self.bus.i2c_rdwr(m)
+        return bytes(m.buf[0:length])
+        
+
+    def write(self, addr: int, data: bytes) -> None:
+        m = self.msg.write(addr, data)
+        self.bus.i2c_rdwr(m)
+
+    def write_read(self, addr: int, data: bytes, length: int) -> bytes:
+        mw = self.msg.write(addr, data)
+        mr = self.msg.read(addr, length)
+        self.bus.i2c_rdwr(mw, mr)
+        return bytes(mr.buf[0:length])
+
+    def open(self) -> None:
+        pass
+
+    def close(self) -> None:
+        pass    
+
+
 class JLinkSwdI2CInterface(I2CInterface):
     GPIO_BASE = {
         'PA': 0x40010800,