Add 16-bit register mock device

tester/device16.go

@@ -0,0 +1,74 @@
+package tester
+
+// I2CDevice represents a mock I2C device on a mock I2C bus with 16-bit registers.
+type I2CDevice16 struct {
+	c Failer
+	// addr is the i2c device address.
+	addr uint8
+	// Registers holds the device registers. It can be inspected
+	// or changed as desired for testing.
+	Registers map[uint8]uint16
+	// If Err is non-nil, it will be returned as the error from the
+	// I2C methods.
+	Err error
+}
+
+// NewI2CDevice returns a new mock I2C device.
+//
+// To use this mock, populate the Registers map with known / expected
+// registers.  Attempts by the code under test to write to a register
+// that has not been populated into the map will be treated as an
+// error.
+func NewI2CDevice16(c Failer, addr uint8) *I2CDevice16 {
+	return &I2CDevice16{
+		c:         c,
+		addr:      addr,
+		Registers: map[uint8]uint16{},
+	}
+}
+
+// Addr returns the Device address.
+func (d *I2CDevice16) Addr() uint8 {
+	return d.addr
+}
+
+// ReadRegister implements I2C.ReadRegister.
+func (d *I2CDevice16) ReadRegister(r uint8, buf []byte) error {
+	if d.Err != nil {
+		return d.Err
+	}
+
+	if len(buf) > 2 {
+		d.c.Fatalf("register read [%#x, %#x] oversized buffer", r, len(buf))
+	}
+
+	val, ok := d.Registers[r]
+	if !ok {
+		d.c.Fatalf("register read [%#x] unknown register", r)
+	}
+
+	buf[0] = byte(val >> 8)
+	buf[1] = byte(val & 0xff)
+
+	return nil
+}
+
+// WriteRegister implements I2C.WriteRegister.
+func (d *I2CDevice16) WriteRegister(r uint8, buf []byte) error {
+	if d.Err != nil {
+		return d.Err
+	}
+
+	if len(buf) != 2 {
+		d.c.Fatalf("register write [%#x, %#x] mis-sized write", r, len(buf))
+	}
+
+	_, ok := d.Registers[r]
+	if !ok {
+		d.c.Fatalf("register write [%#x] unknown register", r)
+	}
+
+	d.Registers[r] = uint16(buf[0])<<8 | uint16(buf[1])
+
+	return nil
+}