File-copy from v4.4.100

This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Please refer to that tree for all history prior to this point.

Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/drivers/iio/magnetometer/st_magn_buffer.c b/drivers/iio/magnetometer/st_magn_buffer.c
new file mode 100644
index 0000000..ecd3bd0
--- /dev/null
+++ b/drivers/iio/magnetometer/st_magn_buffer.c
@@ -0,0 +1,96 @@
+/*
+ * STMicroelectronics magnetometers driver
+ *
+ * Copyright 2012-2013 STMicroelectronics Inc.
+ *
+ * Denis Ciocca <denis.ciocca@st.com>
+ *
+ * Licensed under the GPL-2.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+#include <linux/interrupt.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+
+#include <linux/iio/common/st_sensors.h>
+#include "st_magn.h"
+
+int st_magn_trig_set_state(struct iio_trigger *trig, bool state)
+{
+	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
+
+	return st_sensors_set_dataready_irq(indio_dev, state);
+}
+
+static int st_magn_buffer_preenable(struct iio_dev *indio_dev)
+{
+	return st_sensors_set_enable(indio_dev, true);
+}
+
+static int st_magn_buffer_postenable(struct iio_dev *indio_dev)
+{
+	int err;
+	struct st_sensor_data *mdata = iio_priv(indio_dev);
+
+	mdata->buffer_data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
+	if (mdata->buffer_data == NULL) {
+		err = -ENOMEM;
+		goto allocate_memory_error;
+	}
+
+	err = iio_triggered_buffer_postenable(indio_dev);
+	if (err < 0)
+		goto st_magn_buffer_postenable_error;
+
+	return err;
+
+st_magn_buffer_postenable_error:
+	kfree(mdata->buffer_data);
+allocate_memory_error:
+	return err;
+}
+
+static int st_magn_buffer_predisable(struct iio_dev *indio_dev)
+{
+	int err;
+	struct st_sensor_data *mdata = iio_priv(indio_dev);
+
+	err = iio_triggered_buffer_predisable(indio_dev);
+	if (err < 0)
+		goto st_magn_buffer_predisable_error;
+
+	err = st_sensors_set_enable(indio_dev, false);
+
+st_magn_buffer_predisable_error:
+	kfree(mdata->buffer_data);
+	return err;
+}
+
+static const struct iio_buffer_setup_ops st_magn_buffer_setup_ops = {
+	.preenable = &st_magn_buffer_preenable,
+	.postenable = &st_magn_buffer_postenable,
+	.predisable = &st_magn_buffer_predisable,
+};
+
+int st_magn_allocate_ring(struct iio_dev *indio_dev)
+{
+	return iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time,
+		&st_sensors_trigger_handler, &st_magn_buffer_setup_ops);
+}
+
+void st_magn_deallocate_ring(struct iio_dev *indio_dev)
+{
+	iio_triggered_buffer_cleanup(indio_dev);
+}
+
+MODULE_AUTHOR("Denis Ciocca <denis.ciocca@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics magnetometers buffer");
+MODULE_LICENSE("GPL v2");