iio: add support for binary attributes

When a IIO device is registered, the IIO core creates an attribute group on
its own, where it puts the channel attributes, and where it copies the
attributes in indio_dev->info->attrs.

Unfortunately it doesn't take care of binary attributes (i.e. it only
consider indio_dev->info->attrs->attrs, and it ignores
indio_dev->info->attrs->bin_attrs).

Fix this by making the IIO layer take care also of the binary attributes.

Note that while it is necessary to copy the non-binary attributes because
the IIO layer needs more room to add the channels attribute, it should be
enough to assign the bin_attrs pointer to the binary attributes pointed by
indio_dev->info->attrs->bin_attrs.

Signed-off-by: Andrea Merello <andrea.merello@iit.it>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220907132205.28021-8-andrea.merello@iit.it
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-core.c

@@ -1576,7 +1576,7 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 		ret = -ENOMEM;
 		goto error_clear_attrs;
 	}
-	/* Copy across original attributes */
+	/* Copy across original attributes, and point to original binary attributes */
 	if (indio_dev->info->attrs) {
 		memcpy(iio_dev_opaque->chan_attr_group.attrs,
 		       indio_dev->info->attrs->attrs,
@@ -1584,6 +1584,8 @@ static int iio_device_register_sysfs(struct iio_dev *indio_dev)
 		       *attrcount_orig);
 		iio_dev_opaque->chan_attr_group.is_visible =
 			indio_dev->info->attrs->is_visible;
+		iio_dev_opaque->chan_attr_group.bin_attrs =
+			indio_dev->info->attrs->bin_attrs;
 	}
 	attrn = attrcount_orig;
 	/* Add all elements from the list. */