1 files changed, 433 insertions, 0 deletions
diff --git a/drivers/staging/iio/ring_sw.c b/drivers/staging/iio/ring_sw.c
new file mode 100644
index 000000000000..359ff9208f36
--- /dev/null
+++ b/drivers/staging/iio/ring_sw.c
@@ -0,0 +1,433 @@
+/* The industrial I/O simple minimally locked ring buffer.
+ *
+ * Copyright (c) 2008 Jonathan Cameron
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/workqueue.h>
+#include "ring_sw.h"
+
+static inline int __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
+					    int bytes_per_datum, int length)
+{
+	if ((length == 0) || (bytes_per_datum == 0))
+		return -EINVAL;
+
+	__iio_init_ring_buffer(&ring->buf, bytes_per_datum, length);
+	ring->use_lock = __SPIN_LOCK_UNLOCKED((ring)->use_lock);
+	ring->data = kmalloc(length*ring->buf.bpd, GFP_KERNEL);
+	ring->read_p = 0;
+	ring->write_p = 0;
+	ring->last_written_p = 0;
+	ring->half_p = 0;
+	return ring->data ? 0 : -ENOMEM;
+}
+
+static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
+{
+	kfree(ring->data);
+}
+
+void iio_mark_sw_rb_in_use(struct iio_ring_buffer *r)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	spin_lock(&ring->use_lock);
+	ring->use_count++;
+	spin_unlock(&ring->use_lock);
+}
+EXPORT_SYMBOL(iio_mark_sw_rb_in_use);
+
+void iio_unmark_sw_rb_in_use(struct iio_ring_buffer *r)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	spin_lock(&ring->use_lock);
+	ring->use_count--;
+	spin_unlock(&ring->use_lock);
+}
+EXPORT_SYMBOL(iio_unmark_sw_rb_in_use);
+
+
+/* Ring buffer related functionality */
+/* Store to ring is typically called in the bh of a data ready interrupt handler
+ * in the device driver */
+/* Lock always held if their is a chance this may be called */
+/* Only one of these per ring may run concurrently - enforced by drivers */
+int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
+			 unsigned char *data,
+			 s64 timestamp)
+{
+	int ret = 0;
+	int code;
+	unsigned char *temp_ptr, *change_test_ptr;
+
+	/* initial store */
+	if (unlikely(ring->write_p == 0)) {
+		ring->write_p = ring->data;
+		/* Doesn't actually matter if this is out of the set
+		 * as long as the read pointer is valid before this
+		 * passes it - guaranteed as set later in this function.
+		 */
+		ring->half_p = ring->data - ring->buf.length*ring->buf.bpd/2;
+	}
+	/* Copy data to where ever the current write pointer says */
+	memcpy(ring->write_p, data, ring->buf.bpd);
+	barrier();
+	/* Update the pointer used to get most recent value.
+	 * Always valid as either points to latest or second latest value.
+	 * Before this runs it is null and read attempts fail with -EAGAIN.
+	 */
+	ring->last_written_p = ring->write_p;
+	barrier();
+	/* temp_ptr used to ensure we never have an invalid pointer
+	 * it may be slightly lagging, but never invalid
+	 */
+	temp_ptr = ring->write_p + ring->buf.bpd;
+	/* End of ring, back to the beginning */
+	if (temp_ptr == ring->data + ring->buf.length*ring->buf.bpd)
+		temp_ptr = ring->data;
+	/* Update the write pointer
+	 * always valid as long as this is the only function able to write.
+	 * Care needed with smp systems to ensure more than one ring fill
+	 * is never scheduled.
+	 */
+	ring->write_p = temp_ptr;
+
+	if (ring->read_p == 0)
+		ring->read_p = ring->data;
+	/* Buffer full - move the read pointer and create / escalate
+	 * ring event */
+	/* Tricky case - if the read pointer moves before we adjust it.
+	 * Handle by not pushing if it has moved - may result in occasional
+	 * unnecessary buffer full events when it wasn't quite true.
+	 */
+	else if (ring->write_p == ring->read_p) {
+		change_test_ptr = ring->read_p;
+		temp_ptr = change_test_ptr + ring->buf.bpd;
+		if (temp_ptr
+		    == ring->data + ring->buf.length*ring->buf.bpd) {
+			temp_ptr = ring->data;
+		}
+		/* We are moving pointer on one because the ring is full.  Any
+		 * change to the read pointer will be this or greater.
+		 */
+		if (change_test_ptr == ring->read_p)
+			ring->read_p = temp_ptr;
+
+		spin_lock(&ring->buf.shared_ev_pointer.lock);
+
+		ret = iio_push_or_escallate_ring_event(&ring->buf,
+						       IIO_EVENT_CODE_RING_100_FULL,
+						       timestamp);
+		spin_unlock(&ring->buf.shared_ev_pointer.lock);
+		if (ret)
+			goto error_ret;
+	}
+	/* investigate if our event barrier has been passed */
+	/* There are definite 'issues' with this and chances of
+	 * simultaneous read */
+	/* Also need to use loop count to ensure this only happens once */
+	ring->half_p += ring->buf.bpd;
+	if (ring->half_p == ring->data + ring->buf.length*ring->buf.bpd)
+		ring->half_p = ring->data;
+	if (ring->half_p == ring->read_p) {
+		spin_lock(&ring->buf.shared_ev_pointer.lock);
+		code = IIO_EVENT_CODE_RING_50_FULL;
+		ret = __iio_push_event(&ring->buf.ev_int,
+				       code,
+				       timestamp,
+				       &ring->buf.shared_ev_pointer);
+		spin_unlock(&ring->buf.shared_ev_pointer.lock);
+	}
+error_ret:
+	return ret;
+}
+
+int iio_rip_sw_rb(struct iio_ring_buffer *r,
+		  size_t count, u8 **data, int *dead_offset)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+
+	u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
+	int ret, max_copied;
+	int bytes_to_rip;
+
+	/* A userspace program has probably made an error if it tries to
+	 *  read something that is not a whole number of bpds.
+	 * Return an error.
+	 */
+	if (count % ring->buf.bpd) {
+		ret = -EINVAL;
+		printk(KERN_INFO "Ring buffer read request not whole number of"
+		       "samples: Request bytes %zd, Current bpd %d\n",
+		       count, ring->buf.bpd);
+		goto error_ret;
+	}
+	/* Limit size to whole of ring buffer */
+	bytes_to_rip = min((size_t)(ring->buf.bpd*ring->buf.length), count);
+
+	*data = kmalloc(bytes_to_rip, GFP_KERNEL);
+	if (*data == NULL) {
+		ret = -ENOMEM;
+		goto error_ret;
+	}
+
+	/* build local copy */
+	initial_read_p = ring->read_p;
+	if (unlikely(initial_read_p == 0)) { /* No data here as yet */
+		ret = 0;
+		goto error_free_data_cpy;
+	}
+
+	initial_write_p = ring->write_p;
+
+	/* Need a consistent pair */
+	while ((initial_read_p != ring->read_p)
+	       || (initial_write_p != ring->write_p)) {
+		initial_read_p = ring->read_p;
+		initial_write_p = ring->write_p;
+	}
+	if (initial_write_p == initial_read_p) {
+		/* No new data available.*/
+		ret = 0;
+		goto error_free_data_cpy;
+	}
+
+	if (initial_write_p >= initial_read_p + bytes_to_rip) {
+		/* write_p is greater than necessary, all is easy */
+		max_copied = bytes_to_rip;
+		memcpy(*data, initial_read_p, max_copied);
+		end_read_p = initial_read_p + max_copied;
+	} else if (initial_write_p > initial_read_p) {
+		/*not enough data to cpy */
+		max_copied = initial_write_p - initial_read_p;
+		memcpy(*data, initial_read_p, max_copied);
+		end_read_p = initial_write_p;
+	} else {
+		/* going through 'end' of ring buffer */
+		max_copied = ring->data
+			+ ring->buf.length*ring->buf.bpd - initial_read_p;
+		memcpy(*data, initial_read_p, max_copied);
+		/* possible we are done if we align precisely with end */
+		if (max_copied == bytes_to_rip)
+			end_read_p = ring->data;
+		else if (initial_write_p
+			 > ring->data + bytes_to_rip - max_copied) {
+			/* enough data to finish */
+			memcpy(*data + max_copied, ring->data,
+			       bytes_to_rip - max_copied);
+			max_copied = bytes_to_rip;
+			end_read_p = ring->data + (bytes_to_rip - max_copied);
+		} else {  /* not enough data */
+			memcpy(*data + max_copied, ring->data,
+			       initial_write_p - ring->data);
+			max_copied += initial_write_p - ring->data;
+			end_read_p = initial_write_p;
+		}
+	}
+	/* Now to verify which section was cleanly copied - i.e. how far
+	 * read pointer has been pushed */
+	current_read_p = ring->read_p;
+
+	if (initial_read_p <= current_read_p)
+		*dead_offset = current_read_p - initial_read_p;
+	else
+		*dead_offset = ring->buf.length*ring->buf.bpd
+			- (initial_read_p - current_read_p);
+
+	/* possible issue if the initial write has been lapped or indeed
+	 * the point we were reading to has been passed */
+	/* No valid data read.
+	 * In this case the read pointer is already correct having been
+	 * pushed further than we would look. */
+	if (max_copied - *dead_offset < 0) {
+		ret = 0;
+		goto error_free_data_cpy;
+	}
+
+	/* setup the next read position */
+	/* Beware, this may fail due to concurrency fun and games.
+	 *  Possible that sufficient fill commands have run to push the read
+	 * pointer past where we would be after the rip. If this occurs, leave
+	 * it be.
+	 */
+	/* Tricky - deal with loops */
+
+	while (ring->read_p != end_read_p)
+		ring->read_p = end_read_p;
+
+	return max_copied - *dead_offset;
+
+error_free_data_cpy:
+	kfree(*data);
+error_ret:
+	return ret;
+}
+EXPORT_SYMBOL(iio_rip_sw_rb);
+
+int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	return iio_store_to_sw_ring(ring, data, timestamp);
+}
+EXPORT_SYMBOL(iio_store_to_sw_rb);
+
+int iio_read_last_from_sw_ring(struct iio_sw_ring_buffer *ring,
+			       unsigned char *data)
+{
+	unsigned char *last_written_p_copy;
+
+	iio_mark_sw_rb_in_use(&ring->buf);
+again:
+	barrier();
+	last_written_p_copy = ring->last_written_p;
+	barrier(); /*unnessecary? */
+	/* Check there is anything here */
+	if (last_written_p_copy == 0)
+		return -EAGAIN;
+	memcpy(data, last_written_p_copy, ring->buf.bpd);
+
+	if (unlikely(ring->last_written_p >= last_written_p_copy))
+		goto again;
+
+	iio_unmark_sw_rb_in_use(&ring->buf);
+	return 0;
+}
+
+int iio_read_last_from_sw_rb(struct iio_ring_buffer *r,
+			     unsigned char *data)
+{
+	return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
+}
+EXPORT_SYMBOL(iio_read_last_from_sw_rb);
+
+int iio_request_update_sw_rb(struct iio_ring_buffer *r)
+{
+	int ret = 0;
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+
+	spin_lock(&ring->use_lock);
+	if (!ring->update_needed)
+		goto error_ret;
+	if (ring->use_count) {
+		ret = -EAGAIN;
+		goto error_ret;
+	}
+	__iio_free_sw_ring_buffer(ring);
+	ret = __iio_init_sw_ring_buffer(ring, ring->buf.bpd, ring->buf.length);
+error_ret:
+	spin_unlock(&ring->use_lock);
+	return ret;
+}
+EXPORT_SYMBOL(iio_request_update_sw_rb);
+
+int iio_get_bpd_sw_rb(struct iio_ring_buffer *r)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	return ring->buf.bpd;
+}
+EXPORT_SYMBOL(iio_get_bpd_sw_rb);
+
+int iio_set_bpd_sw_rb(struct iio_ring_buffer *r, size_t bpd)
+{
+	if (r->bpd != bpd) {
+		r->bpd = bpd;
+		if (r->access.mark_param_change)
+			r->access.mark_param_change(r);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(iio_set_bpd_sw_rb);
+
+int iio_get_length_sw_rb(struct iio_ring_buffer *r)
+{
+	return r->length;
+}
+EXPORT_SYMBOL(iio_get_length_sw_rb);
+
+int iio_set_length_sw_rb(struct iio_ring_buffer *r, int length)
+{
+	if (r->length != length) {
+		r->length = length;
+		if (r->access.mark_param_change)
+			r->access.mark_param_change(r);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(iio_set_length_sw_rb);
+
+int iio_mark_update_needed_sw_rb(struct iio_ring_buffer *r)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	ring->update_needed = true;
+	return 0;
+}
+EXPORT_SYMBOL(iio_mark_update_needed_sw_rb);
+
+static void iio_sw_rb_release(struct device *dev)
+{
+	struct iio_ring_buffer *r = to_iio_ring_buffer(dev);
+	kfree(iio_to_sw_ring(r));
+}
+
+static IIO_RING_ENABLE_ATTR;
+static IIO_RING_BPS_ATTR;
+static IIO_RING_LENGTH_ATTR;
+
+/* Standard set of ring buffer attributes */
+static struct attribute *iio_ring_attributes[] = {
+	&dev_attr_length.attr,
+	&dev_attr_bps.attr,
+	&dev_attr_ring_enable.attr,
+	NULL,
+};
+
+static struct attribute_group iio_ring_attribute_group = {
+	.attrs = iio_ring_attributes,
+};
+
+static const struct attribute_group *iio_ring_attribute_groups[] = {
+	&iio_ring_attribute_group,
+	NULL
+};
+
+static struct device_type iio_sw_ring_type = {
+	.release = iio_sw_rb_release,
+	.groups = iio_ring_attribute_groups,
+};
+
+struct iio_ring_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
+{
+	struct iio_ring_buffer *buf;
+	struct iio_sw_ring_buffer *ring;
+
+	ring = kzalloc(sizeof *ring, GFP_KERNEL);
+	if (!ring)
+		return 0;
+	buf = &ring->buf;
+
+	iio_ring_buffer_init(buf, indio_dev);
+	buf->dev.type = &iio_sw_ring_type;
+	device_initialize(&buf->dev);
+	buf->dev.parent = &indio_dev->dev;
+	buf->dev.class = &iio_class;
+	dev_set_drvdata(&buf->dev, (void *)buf);
+
+	return buf;
+}
+EXPORT_SYMBOL(iio_sw_rb_allocate);
+
+void iio_sw_rb_free(struct iio_ring_buffer *r)
+{
+	if (r)
+		iio_put_ring_buffer(r);
+}
+EXPORT_SYMBOL(iio_sw_rb_free);
+MODULE_DESCRIPTION("Industrialio I/O software ring buffer");
+MODULE_LICENSE("GPL");