iio: light: adjd_s311: move buffer on adjd_s311_data object

This change moves the entire buffer on the private adjd_s311_data type.
Since the device has 4 channels, it's not a big waste to just allocate the
maximum possible buffer and use only what's needed.

This is in contrast with free-ing and re-allocating the buffer on the
update_scan_mode hook.

Since the driver pushes buffer data with
iio_push_to_buffers_with_timestamp(), the buffer must also include a
64-bit buffer for the timestamp, for each sample-set.

With this change, the adjd_s311_update_scan_mode() is no longer needed.
Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210705071456.649659-1-aardelean@deviqon.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/adjd_s311.c

@@ -54,7 +54,10 @@
 
 struct adjd_s311_data {
 	struct i2c_client *client;
-	u16 *buffer;
+	struct {
+		s16 chans[4];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 enum adjd_s311_channel_idx {
@@ -129,10 +132,10 @@ static irqreturn_t adjd_s311_trigger_handler(int irq, void *p)
 		if (ret < 0)
 			goto done;
 
-		data->buffer[j++] = ret & ADJD_S311_DATA_MASK;
+		data->scan.chans[j++] = ret & ADJD_S311_DATA_MASK;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data->buffer, time_ns);
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan, time_ns);
 
 done:
 	iio_trigger_notify_done(indio_dev->trig);
@@ -225,23 +228,9 @@ static int adjd_s311_write_raw(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
-static int adjd_s311_update_scan_mode(struct iio_dev *indio_dev,
-	const unsigned long *scan_mask)
-{
-	struct adjd_s311_data *data = iio_priv(indio_dev);
-
-	kfree(data->buffer);
-	data->buffer = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
-	if (data->buffer == NULL)
-		return -ENOMEM;
-
-	return 0;
-}
-
 static const struct iio_info adjd_s311_info = {
 	.read_raw = adjd_s311_read_raw,
 	.write_raw = adjd_s311_write_raw,
-	.update_scan_mode = adjd_s311_update_scan_mode,
 };
 
 static int adjd_s311_probe(struct i2c_client *client,
@@ -286,11 +275,9 @@ static int adjd_s311_probe(struct i2c_client *client,
 static int adjd_s311_remove(struct i2c_client *client)
 {
 	struct iio_dev *indio_dev = i2c_get_clientdata(client);
-	struct adjd_s311_data *data = iio_priv(indio_dev);
 
 	iio_device_unregister(indio_dev);
 	iio_triggered_buffer_cleanup(indio_dev);
-	kfree(data->buffer);
 
 	return 0;
 }