iio: st_sensors: simplify buffer address handling

The driver goes to some length to dynamically allocate an array
to hold the channel addresses. However no ST sensor has more than
three channels (x, y, z at most). Instead of kmalloc():ing and
kfree():in the address array, just use a fixed array of three
elements.

Cc: Giuseppe Barba <giuseppe.barba@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Denis Ciocca <denis.ciocca@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/common/st_sensors/st_sensors_buffer.c

@@ -24,19 +24,13 @@
 
 int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
 {
-	u8 *addr;
+	u8 addr[3]; /* no ST sensor has more than 3 channels */
 	int i, n = 0, len;
 	struct st_sensor_data *sdata = iio_priv(indio_dev);
 	unsigned int num_data_channels = sdata->num_data_channels;
 	unsigned int byte_for_channel =
 			indio_dev->channels[0].scan_type.storagebits >> 3;
 
-	addr = kmalloc(num_data_channels, GFP_KERNEL);
-	if (!addr) {
-		len = -ENOMEM;
-		goto st_sensors_get_buffer_element_error;
-	}
-
 	for (i = 0; i < num_data_channels; i++) {
 		if (test_bit(i, indio_dev->active_scan_mask)) {
 			addr[n] = indio_dev->channels[i].address;
@@ -57,10 +51,8 @@ int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
 			u8 *rx_array;
 			rx_array = kmalloc(byte_for_channel * num_data_channels,
 					   GFP_KERNEL);
-			if (!rx_array) {
-				len = -ENOMEM;
-				goto st_sensors_free_memory;
-			}
+			if (!rx_array)
+				return -ENOMEM;
 
 			len = sdata->tf->read_multiple_byte(&sdata->tb,
 				sdata->dev, addr[0],
@@ -68,7 +60,7 @@ int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
 				rx_array, sdata->multiread_bit);
 			if (len < 0) {
 				kfree(rx_array);
-				goto st_sensors_free_memory;
+				return len;
 			}
 
 			for (i = 0; i < n * byte_for_channel; i++) {
@@ -87,17 +79,11 @@ int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
 			buf, sdata->multiread_bit);
 		break;
 	default:
-		len = -EINVAL;
-		goto st_sensors_free_memory;
-	}
-	if (len != byte_for_channel * n) {
-		len = -EIO;
-		goto st_sensors_free_memory;
+		return -EINVAL;
 	}
+	if (len != byte_for_channel * n)
+		return -EIO;
 
-st_sensors_free_memory:
-	kfree(addr);
-st_sensors_get_buffer_element_error:
 	return len;
 }
 EXPORT_SYMBOL(st_sensors_get_buffer_element);