iio: buffer-callback: allow getting underlying iio_dev

Add iio_channel_cb_get_iio_dev function to allow getting the
underlying iio_dev. This is useful for setting the trigger of the
consumer ADC device.

Signed-off-by: Matt Ranostay <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/buffer/industrialio-buffer-cb.c

···
 	int (*cb)(const void *data, void *private);
 	void *private;
 	struct iio_channel *channels;
+	struct iio_dev *indio_dev;
 };
 
 static struct iio_cb_buffer *buffer_to_cb_buffer(struct iio_buffer *buffer)
···
 {
 	int ret;
 	struct iio_cb_buffer *cb_buff;
-	struct iio_dev *indio_dev;
 	struct iio_channel *chan;
 
 	cb_buff = kzalloc(sizeof(*cb_buff), GFP_KERNEL);
···
 		goto error_free_cb_buff;
 	}
 
-	indio_dev = cb_buff->channels[0].indio_dev;
+	cb_buff->indio_dev = cb_buff->channels[0].indio_dev;
 	cb_buff->buffer.scan_mask
-		= kcalloc(BITS_TO_LONGS(indio_dev->masklength), sizeof(long),
-			  GFP_KERNEL);
+		= kcalloc(BITS_TO_LONGS(cb_buff->indio_dev->masklength),
+			  sizeof(long), GFP_KERNEL);
 	if (cb_buff->buffer.scan_mask == NULL) {
 		ret = -ENOMEM;
 		goto error_release_channels;
 	}
 	chan = &cb_buff->channels[0];
 	while (chan->indio_dev) {
-		if (chan->indio_dev != indio_dev) {
+		if (chan->indio_dev != cb_buff->indio_dev) {
 			ret = -EINVAL;
 			goto error_free_scan_mask;
 		}
···
 
 int iio_channel_start_all_cb(struct iio_cb_buffer *cb_buff)
 {
-	return iio_update_buffers(cb_buff->channels[0].indio_dev,
-				  &cb_buff->buffer,
+	return iio_update_buffers(cb_buff->indio_dev, &cb_buff->buffer,
 				  NULL);
 }
 EXPORT_SYMBOL_GPL(iio_channel_start_all_cb);
 
 void iio_channel_stop_all_cb(struct iio_cb_buffer *cb_buff)
 {
-	iio_update_buffers(cb_buff->channels[0].indio_dev,
-			   NULL,
-			   &cb_buff->buffer);
+	iio_update_buffers(cb_buff->indio_dev, NULL, &cb_buff->buffer);
 }
 EXPORT_SYMBOL_GPL(iio_channel_stop_all_cb);
 
···
 	return cb_buffer->channels;
 }
 EXPORT_SYMBOL_GPL(iio_channel_cb_get_channels);
+
+struct iio_dev
+*iio_channel_cb_get_iio_dev(const struct iio_cb_buffer *cb_buffer)
+{
+	return cb_buffer->indio_dev;
+}
+EXPORT_SYMBOL_GPL(iio_channel_cb_get_iio_dev);
 
 MODULE_AUTHOR("Jonathan Cameron <[e-mail]>");
 MODULE_DESCRIPTION("Industrial I/O callback buffer");

include/linux/iio/consumer.h

···
 *iio_channel_cb_get_channels(const struct iio_cb_buffer *cb_buffer);
 
 /**
+ * iio_channel_cb_get_iio_dev() - get access to the underlying device.
+ * @cb_buffer:		The callback buffer from whom we want the device
+ *			information.
+ *
+ * This function allows one to obtain information about the device.
+ * The primary aim is to allow drivers that are consuming a device to query
+ * things like current trigger.
+ */
+struct iio_dev
+*iio_channel_cb_get_iio_dev(const struct iio_cb_buffer *cb_buffer);
+
+/**
  * iio_read_channel_raw() - read from a given channel
  * @chan:		The channel being queried.
  * @val:		Value read back.