staging:iio: add demux optionally to path from device to buffer

This gives you only what you ask for which is handy
for some devices with weird scan combinations.

Routes all data flow through a core utility function.
That and this demuxing support will be needed to do
demuxing to multiple destinations in kernel.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/buffer.h

@@ -95,6 +95,8 @@ struct iio_buffer_setup_ops {
  * @access:		[DRIVER] buffer access functions associated with the
  *			implementation.
  * @flags:		[INTERN] file ops related flags including busy flag.
+ * @demux_list:		[INTERN] list of operations required to demux the scan.
+ * @demux_bounce:	[INTERN] buffer for doing gather from incoming scan.
  **/
 struct iio_buffer {
 	struct iio_dev				*indio_dev;
@@ -115,6 +117,8 @@ struct iio_buffer {
 	bool					stufftoread;
 	unsigned long				flags;
 	const struct attribute_group *attrs;
+	struct list_head			demux_list;
+	unsigned char				*demux_bounce;
 };
 
 /**
@@ -152,6 +156,17 @@ int iio_scan_mask_set(struct iio_buffer *buffer, int bit);
 #define to_iio_buffer(d)				\
 	container_of(d, struct iio_buffer, dev)
 
+/**
+ * iio_push_to_buffer() - push to a registered buffer.
+ * @buffer:		IIO buffer structure for device
+ * @scan:		Full scan.
+ * @timestamp:
+ */
+int iio_push_to_buffer(struct iio_buffer *buffer, unsigned char *data,
+		       s64 timestamp);
+
+int iio_update_demux(struct iio_dev *indio_dev);
+
 /**
  * iio_buffer_register() - register the buffer with IIO core
  * @indio_dev: device with the buffer to be registered

drivers/staging/iio/industrialio-buffer.c

@@ -87,6 +87,7 @@ void iio_chrdev_buffer_release(struct iio_dev *indio_dev)
 
 void iio_buffer_init(struct iio_buffer *buffer, struct iio_dev *indio_dev)
 {
+	INIT_LIST_HEAD(&buffer->demux_list);
 	buffer->indio_dev = indio_dev;
 	init_waitqueue_head(&buffer->pollq);
 }
@@ -128,10 +129,9 @@ static ssize_t iio_scan_el_show(struct device *dev,
 	int ret;
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 
-	ret = iio_scan_mask_query(indio_dev->buffer,
-				  to_iio_dev_attr(attr)->address);
-	if (ret < 0)
-		return ret;
+	ret = test_bit(to_iio_dev_attr(attr)->address,
+		       indio_dev->buffer->scan_mask);
+
 	return sprintf(buf, "%d\n", ret);
 }
 
@@ -579,6 +579,12 @@ int iio_sw_buffer_preenable(struct iio_dev *indio_dev)
 					    buffer->scan_mask);
 	else
 		indio_dev->active_scan_mask = buffer->scan_mask;
+	iio_update_demux(indio_dev);
+
+	if (indio_dev->info->update_scan_mode)
+		return indio_dev->info
+			->update_scan_mode(indio_dev,
+					   indio_dev->active_scan_mask);
 	return 0;
 }
 EXPORT_SYMBOL(iio_sw_buffer_preenable);
@@ -648,3 +654,135 @@ int iio_scan_mask_query(struct iio_buffer *buffer, int bit)
 	return test_bit(bit, mask);
 };
 EXPORT_SYMBOL_GPL(iio_scan_mask_query);
+
+/**
+ * struct iio_demux_table() - table describing demux memcpy ops
+ * @from:	index to copy from
+ * @to:	index to copy to
+ * @length:	how many bytes to copy
+ * @l:		list head used for management
+ */
+struct iio_demux_table {
+	unsigned from;
+	unsigned to;
+	unsigned length;
+	struct list_head l;
+};
+
+static unsigned char *iio_demux(struct iio_buffer *buffer,
+				 unsigned char *datain)
+{
+	struct iio_demux_table *t;
+
+	if (list_empty(&buffer->demux_list))
+		return datain;
+	list_for_each_entry(t, &buffer->demux_list, l)
+		memcpy(buffer->demux_bounce + t->to,
+		       datain + t->from, t->length);
+
+	return buffer->demux_bounce;
+}
+
+int iio_push_to_buffer(struct iio_buffer *buffer, unsigned char *data,
+		       s64 timestamp)
+{
+	unsigned char *dataout = iio_demux(buffer, data);
+
+	return buffer->access->store_to(buffer, dataout, timestamp);
+}
+EXPORT_SYMBOL_GPL(iio_push_to_buffer);
+
+int iio_update_demux(struct iio_dev *indio_dev)
+{
+	const struct iio_chan_spec *ch;
+	struct iio_buffer *buffer = indio_dev->buffer;
+	int ret, in_ind = -1, out_ind, length;
+	unsigned in_loc = 0, out_loc = 0;
+	struct iio_demux_table *p, *q;
+
+	/* Clear out any old demux */
+	list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
+		list_del(&p->l);
+		kfree(p);
+	}
+	kfree(buffer->demux_bounce);
+	buffer->demux_bounce = NULL;
+
+	/* First work out which scan mode we will actually have */
+	if (bitmap_equal(indio_dev->active_scan_mask,
+			 buffer->scan_mask,
+			 indio_dev->masklength))
+		return 0;
+
+	/* Now we have the two masks, work from least sig and build up sizes */
+	for_each_set_bit(out_ind,
+			 indio_dev->active_scan_mask,
+			 indio_dev->masklength) {
+		in_ind = find_next_bit(indio_dev->active_scan_mask,
+				       indio_dev->masklength,
+				       in_ind + 1);
+		while (in_ind != out_ind) {
+			in_ind = find_next_bit(indio_dev->active_scan_mask,
+					       indio_dev->masklength,
+					       in_ind + 1);
+			ch = iio_find_channel_from_si(indio_dev, in_ind);
+			length = ch->scan_type.storagebits/8;
+			/* Make sure we are aligned */
+			in_loc += length;
+			if (in_loc % length)
+				in_loc += length - in_loc % length;
+		}
+		p = kmalloc(sizeof(*p), GFP_KERNEL);
+		if (p == NULL) {
+			ret = -ENOMEM;
+			goto error_clear_mux_table;
+		}
+		ch = iio_find_channel_from_si(indio_dev, in_ind);
+		length = ch->scan_type.storagebits/8;
+		if (out_loc % length)
+			out_loc += length - out_loc % length;
+		if (in_loc % length)
+			in_loc += length - in_loc % length;
+		p->from = in_loc;
+		p->to = out_loc;
+		p->length = length;
+		list_add_tail(&p->l, &buffer->demux_list);
+		out_loc += length;
+		in_loc += length;
+	}
+	/* Relies on scan_timestamp being last */
+	if (buffer->scan_timestamp) {
+		p = kmalloc(sizeof(*p), GFP_KERNEL);
+		if (p == NULL) {
+			ret = -ENOMEM;
+			goto error_clear_mux_table;
+		}
+		ch = iio_find_channel_from_si(indio_dev,
+			buffer->scan_index_timestamp);
+		length = ch->scan_type.storagebits/8;
+		if (out_loc % length)
+			out_loc += length - out_loc % length;
+		if (in_loc % length)
+			in_loc += length - in_loc % length;
+		p->from = in_loc;
+		p->to = out_loc;
+		p->length = length;
+		list_add_tail(&p->l, &buffer->demux_list);
+		out_loc += length;
+		in_loc += length;
+	}
+	buffer->demux_bounce = kzalloc(out_loc, GFP_KERNEL);
+	if (buffer->demux_bounce == NULL) {
+		ret = -ENOMEM;
+		goto error_clear_mux_table;
+	}
+	return 0;
+
+error_clear_mux_table:
+	list_for_each_entry_safe(p, q, &buffer->demux_list, l) {
+		list_del(&p->l);
+		kfree(p);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_update_demux);