iio: accel: kxsd9: Split out transport mechanism

Split off a transport mechanism struct that will deal with the SPI
traffic in preparation for adding I2C support.
Tested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/kxsd9.c

@@ -43,18 +43,36 @@
 
 #define KXSD9_STATE_RX_SIZE 2
 #define KXSD9_STATE_TX_SIZE 2
+
+struct kxsd9_transport;
+
+/**
+ * struct kxsd9_transport - transport adapter for SPI or I2C
+ * @trdev: transport device such as SPI or I2C
+ * @write1(): function to write a byte to the device
+ * @write2(): function to write two consecutive bytes to the device
+ * @readval(): function to read a 16bit value from the device
+ * @rx: cache aligned read buffer
+ * @tx: cache aligned write buffer
+ */
+struct kxsd9_transport {
+	void *trdev;
+	int (*write1) (struct kxsd9_transport *tr, u8 byte);
+	int (*write2) (struct kxsd9_transport *tr, u8 b1, u8 b2);
+	int (*readval) (struct kxsd9_transport *tr, u8 address);
+	u8 rx[KXSD9_STATE_RX_SIZE] ____cacheline_aligned;
+	u8 tx[KXSD9_STATE_TX_SIZE];
+};
+
 /**
  * struct kxsd9_state - device related storage
+ * @transport:	transport for the KXSD9
  * @buf_lock:	protect the rx and tx buffers.
  * @us:		spi device
- * @rx:		single rx buffer storage
- * @tx:		single tx buffer storage
  **/
 struct kxsd9_state {
+	struct kxsd9_transport *transport;
 	struct mutex buf_lock;
-	struct spi_device *us;
-	u8 rx[KXSD9_STATE_RX_SIZE] ____cacheline_aligned;
-	u8 tx[KXSD9_STATE_TX_SIZE];
 };
 
 #define KXSD9_SCALE_2G "0.011978"
@@ -80,13 +98,12 @@ static int kxsd9_write_scale(struct iio_dev *indio_dev, int micro)
 		return -EINVAL;
 
 	mutex_lock(&st->buf_lock);
-	ret = spi_w8r8(st->us, KXSD9_READ(KXSD9_REG_CTRL_C));
-	if (ret < 0)
+	ret = st->transport->write1(st->transport, KXSD9_READ(KXSD9_REG_CTRL_C));
+	if (ret)
 		goto error_ret;
-	st->tx[0] = KXSD9_WRITE(KXSD9_REG_CTRL_C);
-	st->tx[1] = (ret & ~KXSD9_FS_MASK) | i;
-
-	ret = spi_write(st->us, st->tx, 2);
+	ret = st->transport->write2(st->transport,
+				    KXSD9_WRITE(KXSD9_REG_CTRL_C),
+				    (ret & ~KXSD9_FS_MASK) | i);
 error_ret:
 	mutex_unlock(&st->buf_lock);
 	return ret;
@@ -96,24 +113,9 @@ static int kxsd9_read(struct iio_dev *indio_dev, u8 address)
 {
 	int ret;
 	struct kxsd9_state *st = iio_priv(indio_dev);
-	struct spi_transfer xfers[] = {
-		{
-			.bits_per_word = 8,
-			.len = 1,
-			.delay_usecs = 200,
-			.tx_buf = st->tx,
-		}, {
-			.bits_per_word = 8,
-			.len = 2,
-			.rx_buf = st->rx,
-		},
-	};
 
 	mutex_lock(&st->buf_lock);
-	st->tx[0] = KXSD9_READ(address);
-	ret = spi_sync_transfer(st->us, xfers, ARRAY_SIZE(xfers));
-	if (!ret)
-		ret = (((u16)(st->rx[0])) << 8) | (st->rx[1] & 0xF0);
+	ret = st->transport->readval(st->transport, KXSD9_READ(address));
 	mutex_unlock(&st->buf_lock);
 	return ret;
 }
@@ -163,8 +165,8 @@ static int kxsd9_read_raw(struct iio_dev *indio_dev,
 		ret = IIO_VAL_INT;
 		break;
 	case IIO_CHAN_INFO_SCALE:
-		ret = spi_w8r8(st->us, KXSD9_READ(KXSD9_REG_CTRL_C));
-		if (ret < 0)
+		ret = st->transport->write1(st->transport, KXSD9_READ(KXSD9_REG_CTRL_C));
+		if (ret)
 			goto error_ret;
 		*val = 0;
 		*val2 = kxsd9_micro_scales[ret & KXSD9_FS_MASK];
@@ -203,15 +205,10 @@ static int kxsd9_power_up(struct kxsd9_state *st)
 {
 	int ret;
 
-	st->tx[0] = 0x0d;
-	st->tx[1] = 0x40;
-	ret = spi_write(st->us, st->tx, 2);
+	ret = st->transport->write2(st->transport, 0x0d, 0x40);
 	if (ret)
 		return ret;
-
-	st->tx[0] = 0x0c;
-	st->tx[1] = 0x9b;
-	return spi_write(st->us, st->tx, 2);
+	return st->transport->write2(st->transport, 0x0c, 0x9b);
 };
 
 static const struct iio_info kxsd9_info = {
@@ -221,56 +218,130 @@ static const struct iio_info kxsd9_info = {
 	.driver_module = THIS_MODULE,
 };
 
-static int kxsd9_probe(struct spi_device *spi)
+static int kxsd9_common_probe(struct device *parent,
+			      struct kxsd9_transport *transport,
+			      const char *name,
+			      struct iio_dev **retdev)
 {
 	struct iio_dev *indio_dev;
 	struct kxsd9_state *st;
+	int ret;
 
-	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	indio_dev = devm_iio_device_alloc(parent, sizeof(*st));
 	if (!indio_dev)
 		return -ENOMEM;
 
 	st = iio_priv(indio_dev);
-	spi_set_drvdata(spi, indio_dev);
+	st->transport = transport;
 
-	st->us = spi;
 	mutex_init(&st->buf_lock);
 	indio_dev->channels = kxsd9_channels;
 	indio_dev->num_channels = ARRAY_SIZE(kxsd9_channels);
-	indio_dev->name = spi_get_device_id(spi)->name;
-	indio_dev->dev.parent = &spi->dev;
+	indio_dev->name = name;
+	indio_dev->dev.parent = parent;
 	indio_dev->info = &kxsd9_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	kxsd9_power_up(st);
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		return ret;
+
+	*retdev = indio_dev;
+	return 0;
+}
+
+static int kxsd9_spi_write1(struct kxsd9_transport *tr, u8 byte)
+{
+	struct spi_device *spi = tr->trdev;
+
+	return spi_w8r8(spi, byte);
+}
+
+static int kxsd9_spi_write2(struct kxsd9_transport *tr, u8 b1, u8 b2)
+{
+	struct spi_device *spi = tr->trdev;
+
+	tr->tx[0] = b1;
+	tr->tx[1] = b2;
+	return spi_write(spi, tr->tx, 2);
+}
+
+static int kxsd9_spi_readval(struct kxsd9_transport *tr, u8 address)
+{
+	struct spi_device *spi = tr->trdev;
+	struct spi_transfer xfers[] = {
+		{
+			.bits_per_word = 8,
+			.len = 1,
+			.delay_usecs = 200,
+			.tx_buf = tr->tx,
+		}, {
+			.bits_per_word = 8,
+			.len = 2,
+			.rx_buf = tr->rx,
+		},
+	};
+	int ret;
+
+	tr->tx[0] = address;
+	ret = spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers));
+	if (!ret)
+		ret = (((u16)(tr->rx[0])) << 8) | (tr->rx[1] & 0xF0);
+	return ret;
+}
+
+static int kxsd9_spi_probe(struct spi_device *spi)
+{
+	struct kxsd9_transport *transport;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	transport = devm_kzalloc(&spi->dev, sizeof(*transport), GFP_KERNEL);
+	if (!transport)
+		return -ENOMEM;
+
+	transport->trdev = spi;
+	transport->write1 = kxsd9_spi_write1;
+	transport->write2 = kxsd9_spi_write2;
+	transport->readval = kxsd9_spi_readval;
 	spi->mode = SPI_MODE_0;
 	spi_setup(spi);
-	kxsd9_power_up(st);
 
-	return iio_device_register(indio_dev);
+	ret = kxsd9_common_probe(&spi->dev,
+				 transport,
+				 spi_get_device_id(spi)->name,
+				 &indio_dev);
+	if (ret)
+		return ret;
+
+	spi_set_drvdata(spi, indio_dev);
+	return 0;
 }
 
-static int kxsd9_remove(struct spi_device *spi)
+static int kxsd9_spi_remove(struct spi_device *spi)
 {
 	iio_device_unregister(spi_get_drvdata(spi));
 
 	return 0;
 }
 
-static const struct spi_device_id kxsd9_id[] = {
+static const struct spi_device_id kxsd9_spi_id[] = {
 	{"kxsd9", 0},
 	{ },
 };
-MODULE_DEVICE_TABLE(spi, kxsd9_id);
+MODULE_DEVICE_TABLE(spi, kxsd9_spi_id);
 
-static struct spi_driver kxsd9_driver = {
+static struct spi_driver kxsd9_spi_driver = {
 	.driver = {
 		.name = "kxsd9",
 	},
-	.probe = kxsd9_probe,
-	.remove = kxsd9_remove,
-	.id_table = kxsd9_id,
+	.probe = kxsd9_spi_probe,
+	.remove = kxsd9_spi_remove,
+	.id_table = kxsd9_spi_id,
 };
-module_spi_driver(kxsd9_driver);
+module_spi_driver(kxsd9_spi_driver);
 
 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
 MODULE_DESCRIPTION("Kionix KXSD9 SPI driver");