Add 16-bit register mock device

tester/device.go

@@ -1,61 +1,15 @@
 package tester
 
 // MaxRegisters is the maximum number of registers supported for a Device.
-const MaxRegisters = 200
+const MaxRegisters = 255
 
-// I2CDevice represents a mock I2C device on a mock I2C bus.
-type I2CDevice 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 [MaxRegisters]uint8
-	// If Err is non-nil, it will be returned as the error from the
-	// I2C methods.
-	Err error
-}
+type I2CDevice interface {
+	// ReadRegister implements I2C.ReadRegister.
+	ReadRegister(r uint8, buf []byte) error
 
-// NewI2CDevice returns a new mock I2C device.
-func NewI2CDevice(c Failer, addr uint8) *I2CDevice {
-	return &I2CDevice{
-		c:    c,
-		addr: addr,
-	}
-}
+	// WriteRegister implements I2C.WriteRegister.
+	WriteRegister(r uint8, buf []byte) error
 
-// Addr returns the Device address.
-func (d *I2CDevice) Addr() uint8 {
-	return d.addr
-}
-
-// ReadRegister implements I2C.ReadRegister.
-func (d *I2CDevice) ReadRegister(r uint8, buf []byte) error {
-	if d.Err != nil {
-		return d.Err
-	}
-	d.assertRegisterRange(r, buf)
-	copy(buf, d.Registers[r:])
-	return nil
-}
-
-// WriteRegister implements I2C.WriteRegister.
-func (d *I2CDevice) WriteRegister(r uint8, buf []byte) error {
-	if d.Err != nil {
-		return d.Err
-	}
-	d.assertRegisterRange(r, buf)
-	copy(d.Registers[r:], buf)
-	return nil
-}
-
-// assertRegisterRange asserts that reading or writing the given
-// register and subsequent registers is in range of the available registers.
-func (d *I2CDevice) assertRegisterRange(r uint8, buf []byte) {
-	if int(r) >= len(d.Registers) {
-		d.c.Fatalf("register read/write [%#x, %#x] start out of range", r, int(r)+len(buf))
-	}
-	if int(r)+len(buf) > len(d.Registers) {
-		d.c.Fatalf("register read/write [%#x, %#x] end out of range", r, int(r)+len(buf))
-	}
+	// Addr returns the Device address.
+	Addr() uint8
 }