iio:adc:max1363 support SMBus for 8-bit devices

The driver currently supports only I2C access. But supported devices with an
accuracy of 8-bit are compatible with the SMBus byte access routines.

This patch wraps the send and receive routines depending on the chip
accuracy and fonctionnalities of its adapter.

For instance, this allows us to use a MAX11603 on a ICH7 controller.

This patch also simplifies the max1363_write_basic_config() routine to
use the struct max1363_state fields directly.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/max1363.c

@@ -165,6 +165,8 @@ struct max1363_chip_info {
  * @thresh_low:		low threshold values
  * @vref:		Reference voltage regulator
  * @vref_uv:		Actual (external or internal) reference voltage
+ * @send:		function used to send data to the chip
+ * @recv:		function used to receive data from the chip
  */
 struct max1363_state {
 	struct i2c_client		*client;
@@ -186,6 +188,10 @@ struct max1363_state {
 	s16				thresh_low[8];
 	struct regulator		*vref;
 	u32				vref_uv;
+	int				(*send)(const struct i2c_client *client,
+						const char *buf, int count);
+	int				(*recv)(const struct i2c_client *client,
+						char *buf, int count);
 };
 
 #define MAX1363_MODE_SINGLE(_num, _mask) {				\
@@ -311,13 +317,37 @@ static const struct max1363_mode
 	return NULL;
 }
 
-static int max1363_write_basic_config(struct i2c_client *client,
-				      unsigned char d1,
-				      unsigned char d2)
+static int max1363_smbus_send(const struct i2c_client *client, const char *buf,
+		int count)
 {
-	u8 tx_buf[2] = {d1, d2};
+	int i, err;
 
-	return i2c_master_send(client, tx_buf, 2);
+	for (i = err = 0; err == 0 && i < count; ++i)
+		err = i2c_smbus_write_byte(client, buf[i]);
+
+	return err ? err : count;
+}
+
+static int max1363_smbus_recv(const struct i2c_client *client, char *buf,
+		int count)
+{
+	int i, ret;
+
+	for (i = 0; i < count; ++i) {
+		ret = i2c_smbus_read_byte(client);
+		if (ret < 0)
+			return ret;
+		buf[i] = ret;
+	}
+
+	return count;
+}
+
+static int max1363_write_basic_config(struct max1363_state *st)
+{
+	u8 tx_buf[2] = { st->setupbyte, st->configbyte };
+
+	return st->send(st->client, tx_buf, 2);
 }
 
 static int max1363_set_scan_mode(struct max1363_state *st)
@@ -327,9 +357,7 @@ static int max1363_set_scan_mode(struct max1363_state *st)
 			    | MAX1363_SE_DE_MASK);
 	st->configbyte |= st->current_mode->conf;
 
-	return max1363_write_basic_config(st->client,
-					  st->setupbyte,
-					  st->configbyte);
+	return max1363_write_basic_config(st);
 }
 
 static int max1363_read_single_chan(struct iio_dev *indio_dev,
@@ -366,7 +394,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
 	}
 	if (st->chip_info->bits != 8) {
 		/* Get reading */
-		data = i2c_master_recv(client, rxbuf, 2);
+		data = st->recv(client, rxbuf, 2);
 		if (data < 0) {
 			ret = data;
 			goto error_ret;
@@ -375,7 +403,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
 		  ((1 << st->chip_info->bits) - 1);
 	} else {
 		/* Get reading */
-		data = i2c_master_recv(client, rxbuf, 1);
+		data = st->recv(client, rxbuf, 1);
 		if (data < 0) {
 			ret = data;
 			goto error_ret;
@@ -772,11 +800,11 @@ static irqreturn_t max1363_event_handler(int irq, void *private)
 	u8 tx[2] = { st->setupbyte,
 		     MAX1363_MON_INT_ENABLE | (st->monitor_speed << 1) | 0xF0 };
 
-	i2c_master_recv(st->client, &rx, 1);
+	st->recv(st->client, &rx, 1);
 	mask = rx;
 	for_each_set_bit(loc, &mask, 8)
 		iio_push_event(indio_dev, max1363_event_codes[loc], timestamp);
-	i2c_master_send(st->client, tx, 2);
+	st->send(st->client, tx, 2);
 
 	return IRQ_HANDLED;
 }
@@ -812,9 +840,7 @@ static int max1363_monitor_mode_update(struct max1363_state *st, int enabled)
 		st->setupbyte &= ~MAX1363_SETUP_MONITOR_SETUP;
 		st->configbyte &= ~MAX1363_SCAN_MASK;
 		st->monitor_on = false;
-		return max1363_write_basic_config(st->client,
-						st->setupbyte,
-						st->configbyte);
+		return max1363_write_basic_config(st);
 	}
 
 	/* Ensure we are in the relevant mode */
@@ -876,7 +902,7 @@ static int max1363_monitor_mode_update(struct max1363_state *st, int enabled)
 		}
 
 
-	ret = i2c_master_send(st->client, tx_buf, len);
+	ret = st->send(st->client, tx_buf, len);
 	if (ret < 0)
 		goto error_ret;
 	if (ret != len) {
@@ -893,7 +919,7 @@ static int max1363_monitor_mode_update(struct max1363_state *st, int enabled)
 	 */
 	tx_buf[0] = st->setupbyte;
 	tx_buf[1] = MAX1363_MON_INT_ENABLE | (st->monitor_speed << 1) | 0xF0;
-	ret = i2c_master_send(st->client, tx_buf, 2);
+	ret = st->send(st->client, tx_buf, 2);
 	if (ret < 0)
 		goto error_ret;
 	if (ret != 2) {
@@ -1481,9 +1507,9 @@ static irqreturn_t max1363_trigger_handler(int irq, void *p)
 	if (rxbuf == NULL)
 		goto done;
 	if (st->chip_info->bits != 8)
-		b_sent = i2c_master_recv(st->client, rxbuf, numvals*2);
+		b_sent = st->recv(st->client, rxbuf, numvals * 2);
 	else
-		b_sent = i2c_master_recv(st->client, rxbuf, numvals);
+		b_sent = st->recv(st->client, rxbuf, numvals);
 	if (b_sent < 0)
 		goto done_free;
 
@@ -1550,6 +1576,18 @@ static int max1363_probe(struct i2c_client *client,
 		st->vref_uv = vref_uv;
 	}
 
+	if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		st->send = i2c_master_send;
+		st->recv = i2c_master_recv;
+	} else if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE)
+			&& st->chip_info->bits == 8) {
+		st->send = max1363_smbus_send;
+		st->recv = max1363_smbus_recv;
+	} else {
+		ret = -EOPNOTSUPP;
+		goto error_disable_reg;
+	}
+
 	ret = max1363_alloc_scan_masks(indio_dev);
 	if (ret)
 		goto error_disable_reg;