1 files changed, 33 insertions, 118 deletions

diff --git a/drivers/staging/iio/ring_sw.c b/drivers/staging/iio/ring_sw.c
index 66a34addb75f..3e24ec455854 100644
--- a/drivers/staging/iio/ring_sw.c
+++ b/drivers/staging/iio/ring_sw.c
@@ -23,11 +23,8 @@
  * @data:		the ring buffer memory
  * @read_p:		read pointer (oldest available)
  * @write_p:		write pointer
- * @last_written_p:	read pointer (newest available)
  * @half_p:		half buffer length behind write_p (event generation)
- * @use_count:		reference count to prevent resizing when in use
  * @update_needed:	flag to indicated change in size requested
- * @use_lock:		lock to prevent change in size when in use
  *
  * Note that the first element of all ring buffers must be a
  * struct iio_buffer.
@@ -37,12 +34,9 @@ struct iio_sw_ring_buffer {
 	unsigned char		*data;
 	unsigned char		*read_p;
 	unsigned char		*write_p;
-	unsigned char		*last_written_p;
 	/* used to act as a point at which to signal an event */
 	unsigned char		*half_p;
-	int			use_count;
 	int			update_needed;
-	spinlock_t		use_lock;
 };
 
 #define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf)
@@ -56,38 +50,15 @@ static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
 	ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC);
 	ring->read_p = NULL;
 	ring->write_p = NULL;
-	ring->last_written_p = NULL;
 	ring->half_p = NULL;
 	return ring->data ? 0 : -ENOMEM;
 }
 
-static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
-{
-	spin_lock_init(&ring->use_lock);
-}
-
 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
 {
 	kfree(ring->data);
 }
 
-static void iio_mark_sw_rb_in_use(struct iio_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);
-}
-
-static void iio_unmark_sw_rb_in_use(struct iio_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);
-}
-
-
 /* Ring buffer related functionality */
 /* Store to ring is typically called in the bh of a data ready interrupt handler
  * in the device driver */
@@ -115,7 +86,6 @@ static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
 	 * 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
@@ -174,6 +144,7 @@ static int iio_read_first_n_sw_rb(struct iio_buffer *r,
 	u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
 	u8 *data;
 	int ret, max_copied, bytes_to_rip, dead_offset;
+	size_t data_available, buffer_size;
 
 	/* A userspace program has probably made an error if it tries to
 	 *  read something that is not a whole number of bpds.
@@ -186,9 +157,11 @@ static int iio_read_first_n_sw_rb(struct iio_buffer *r,
 		       n, ring->buf.bytes_per_datum);
 		goto error_ret;
 	}
+
+	buffer_size = ring->buf.bytes_per_datum*ring->buf.length;
+
 	/* Limit size to whole of ring buffer */
-	bytes_to_rip = min((size_t)(ring->buf.bytes_per_datum*ring->buf.length),
-			   n);
+	bytes_to_rip = min_t(size_t, buffer_size, n);
 
 	data = kmalloc(bytes_to_rip, GFP_KERNEL);
 	if (data == NULL) {
@@ -217,38 +190,24 @@ static int iio_read_first_n_sw_rb(struct iio_buffer *r,
 		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;
+	if (initial_write_p >= initial_read_p)
+		data_available = initial_write_p - initial_read_p;
+	else
+		data_available = buffer_size - (initial_read_p - initial_write_p);
+
+	if (data_available < bytes_to_rip)
+		bytes_to_rip = data_available;
+
+	if (initial_read_p + bytes_to_rip >= ring->data + buffer_size) {
+		max_copied = ring->data + buffer_size - initial_read_p;
 		memcpy(data, initial_read_p, max_copied);
-		end_read_p = initial_write_p;
+		memcpy(data + max_copied, ring->data, bytes_to_rip - max_copied);
+		end_read_p = ring->data + bytes_to_rip - max_copied;
 	} else {
-		/* going through 'end' of ring buffer */
-		max_copied = ring->data
-			+ ring->buf.length*ring->buf.bytes_per_datum - 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;
-		}
+		memcpy(data, initial_read_p, bytes_to_rip);
+		end_read_p = initial_read_p + bytes_to_rip;
 	}
+
 	/* Now to verify which section was cleanly copied - i.e. how far
 	 * read pointer has been pushed */
 	current_read_p = ring->read_p;
@@ -256,15 +215,14 @@ static int iio_read_first_n_sw_rb(struct iio_buffer *r,
 	if (initial_read_p <= current_read_p)
 		dead_offset = current_read_p - initial_read_p;
 	else
-		dead_offset = ring->buf.length*ring->buf.bytes_per_datum
-			- (initial_read_p - current_read_p);
+		dead_offset = buffer_size - (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) {
+	if (bytes_to_rip - dead_offset < 0) {
 		ret = 0;
 		goto error_free_data_cpy;
 	}
@@ -280,7 +238,7 @@ static int iio_read_first_n_sw_rb(struct iio_buffer *r,
 	while (ring->read_p != end_read_p)
 		ring->read_p = end_read_p;
 
-	ret = max_copied - dead_offset;
+	ret = bytes_to_rip - dead_offset;
 
 	if (copy_to_user(buf, data + dead_offset, ret))  {
 		ret =  -EFAULT;
@@ -305,52 +263,18 @@ static int iio_store_to_sw_rb(struct iio_buffer *r,
 	return iio_store_to_sw_ring(ring, data, timestamp);
 }
 
-static 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 == NULL)
-		return -EAGAIN;
-	memcpy(data, last_written_p_copy, ring->buf.bytes_per_datum);
-
-	if (unlikely(ring->last_written_p != last_written_p_copy))
-		goto again;
-
-	iio_unmark_sw_rb_in_use(&ring->buf);
-	return 0;
-}
-
-static int iio_read_last_from_sw_rb(struct iio_buffer *r,
-			     unsigned char *data)
-{
-	return iio_read_last_from_sw_ring(iio_to_sw_ring(r), data);
-}
-
 static int iio_request_update_sw_rb(struct iio_buffer *r)
 {
 	int ret = 0;
 	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 
 	r->stufftoread = false;
-	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_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
 					    ring->buf.length);
 error_ret:
-	spin_unlock(&ring->use_lock);
 	return ret;
 }
 
@@ -360,12 +284,18 @@ static int iio_get_bytes_per_datum_sw_rb(struct iio_buffer *r)
 	return ring->buf.bytes_per_datum;
 }
 
+static int iio_mark_update_needed_sw_rb(struct iio_buffer *r)
+{
+	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
+	ring->update_needed = true;
+	return 0;
+}
+
 static int iio_set_bytes_per_datum_sw_rb(struct iio_buffer *r, size_t bpd)
 {
 	if (r->bytes_per_datum != bpd) {
 		r->bytes_per_datum = bpd;
-		if (r->access->mark_param_change)
-			r->access->mark_param_change(r);
+		iio_mark_update_needed_sw_rb(r);
 	}
 	return 0;
 }
@@ -379,27 +309,17 @@ static int iio_set_length_sw_rb(struct iio_buffer *r, int length)
 {
 	if (r->length != length) {
 		r->length = length;
-		if (r->access->mark_param_change)
-			r->access->mark_param_change(r);
+		iio_mark_update_needed_sw_rb(r);
 	}
 	return 0;
 }
 
-static int iio_mark_update_needed_sw_rb(struct iio_buffer *r)
-{
-	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
-	ring->update_needed = true;
-	return 0;
-}
-
 static IIO_BUFFER_ENABLE_ATTR;
-static IIO_BUFFER_BYTES_PER_DATUM_ATTR;
 static IIO_BUFFER_LENGTH_ATTR;
 
 /* Standard set of ring buffer attributes */
 static struct attribute *iio_ring_attributes[] = {
 	&dev_attr_length.attr,
-	&dev_attr_bytes_per_datum.attr,
 	&dev_attr_enable.attr,
 	NULL,
 };
@@ -419,8 +339,7 @@ struct iio_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
 		return NULL;
 	ring->update_needed = true;
 	buf = &ring->buf;
-	iio_buffer_init(buf, indio_dev);
-	__iio_init_sw_ring_buffer(ring);
+	iio_buffer_init(buf);
 	buf->attrs = &iio_ring_attribute_group;
 
 	return buf;
@@ -434,12 +353,8 @@ void iio_sw_rb_free(struct iio_buffer *r)
 EXPORT_SYMBOL(iio_sw_rb_free);
 
 const struct iio_buffer_access_funcs ring_sw_access_funcs = {
-	.mark_in_use = &iio_mark_sw_rb_in_use,
-	.unmark_in_use = &iio_unmark_sw_rb_in_use,
 	.store_to = &iio_store_to_sw_rb,
-	.read_last = &iio_read_last_from_sw_rb,
 	.read_first_n = &iio_read_first_n_sw_rb,
-	.mark_param_change = &iio_mark_update_needed_sw_rb,
 	.request_update = &iio_request_update_sw_rb,
 	.get_bytes_per_datum = &iio_get_bytes_per_datum_sw_rb,
 	.set_bytes_per_datum = &iio_set_bytes_per_datum_sw_rb,