iio: buffer: use struct iio_scan_type to simplify code

By using struct iio_scan_type, we can simplify the code by removing
lots of duplicate pointer dereferences. This make the code a bit easier
to read.

This also prepares for a future where channels may have more than one
scan_type.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240530-iio-add-support-for-multiple-scan-types-v3-2-cbc4acea2cfa@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/industrialio-buffer.c

@@ -400,7 +400,8 @@ static ssize_t iio_show_fixed_type(struct device *dev,
 				   char *buf)
 {
 	struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
-	u8 type = this_attr->c->scan_type.endianness;
+	const struct iio_scan_type *scan_type = &this_attr->c->scan_type;
+	u8 type = scan_type->endianness;
 
 	if (type == IIO_CPU) {
 #ifdef __LITTLE_ENDIAN
@@ -409,21 +410,21 @@ static ssize_t iio_show_fixed_type(struct device *dev,
 		type = IIO_BE;
 #endif
 	}
-	if (this_attr->c->scan_type.repeat > 1)
+	if (scan_type->repeat > 1)
 		return sysfs_emit(buf, "%s:%c%d/%dX%d>>%u\n",
 		       iio_endian_prefix[type],
-		       this_attr->c->scan_type.sign,
-		       this_attr->c->scan_type.realbits,
-		       this_attr->c->scan_type.storagebits,
-		       this_attr->c->scan_type.repeat,
-		       this_attr->c->scan_type.shift);
+		       scan_type->sign,
+		       scan_type->realbits,
+		       scan_type->storagebits,
+		       scan_type->repeat,
+		       scan_type->shift);
 	else
 		return sysfs_emit(buf, "%s:%c%d/%d>>%u\n",
 		       iio_endian_prefix[type],
-		       this_attr->c->scan_type.sign,
-		       this_attr->c->scan_type.realbits,
-		       this_attr->c->scan_type.storagebits,
-		       this_attr->c->scan_type.shift);
+		       scan_type->sign,
+		       scan_type->realbits,
+		       scan_type->storagebits,
+		       scan_type->shift);
 }
 
 static ssize_t iio_scan_el_show(struct device *dev,
@@ -735,12 +736,16 @@ static unsigned int iio_storage_bytes_for_si(struct iio_dev *indio_dev,
 					     unsigned int scan_index)
 {
 	const struct iio_chan_spec *ch;
+	const struct iio_scan_type *scan_type;
 	unsigned int bytes;
 
 	ch = iio_find_channel_from_si(indio_dev, scan_index);
-	bytes = ch->scan_type.storagebits / 8;
-	if (ch->scan_type.repeat > 1)
-		bytes *= ch->scan_type.repeat;
+	scan_type = &ch->scan_type;
+	bytes = scan_type->storagebits / 8;
+
+	if (scan_type->repeat > 1)
+		bytes *= scan_type->repeat;
+
 	return bytes;
 }
 
@@ -1889,18 +1894,21 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
 	if (channels) {
 		/* new magic */
 		for (i = 0; i < indio_dev->num_channels; i++) {
+			const struct iio_scan_type *scan_type;
+
 			if (channels[i].scan_index < 0)
 				continue;
 
+			scan_type = &channels[i].scan_type;
+
 			/* Verify that sample bits fit into storage */
-			if (channels[i].scan_type.storagebits <
-			    channels[i].scan_type.realbits +
-			    channels[i].scan_type.shift) {
+			if (scan_type->storagebits <
+			    scan_type->realbits + scan_type->shift) {
 				dev_err(&indio_dev->dev,
 					"Channel %d storagebits (%d) < shifted realbits (%d + %d)\n",
-					i, channels[i].scan_type.storagebits,
-					channels[i].scan_type.realbits,
-					channels[i].scan_type.shift);
+					i, scan_type->storagebits,
+					scan_type->realbits,
+					scan_type->shift);
 				ret = -EINVAL;
 				goto error_cleanup_dynamic;
 			}