staging:iio:buffering move the copy to user on rip down into implementations

The current interface is not as adaptable as it should be. Moving
this complexity into the implementations makes it easier to add
new implementations.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Tested-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/industrialio-ring.c

@@ -16,7 +16,6 @@
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/fs.h>
-#include <linux/poll.h>
 #include <linux/cdev.h>
 #include <linux/slab.h>
 
@@ -98,31 +97,13 @@ static ssize_t iio_ring_rip_outer(struct file *filp, char __user *buf,
 				  size_t count, loff_t *f_ps)
 {
 	struct iio_ring_buffer *rb = filp->private_data;
-	int ret, dead_offset, copied;
-	u8 *data;
+	int ret, dead_offset;
+
 	/* rip lots must exist. */
 	if (!rb->access.rip_lots)
 		return -EINVAL;
-	copied = rb->access.rip_lots(rb, count, &data, &dead_offset);
+	ret = rb->access.rip_lots(rb, count, buf, &dead_offset);
 
-	if (copied <= 0) {
-		ret = copied;
-		goto error_ret;
-	}
-	if (copy_to_user(buf, data + dead_offset, copied))  {
-		ret =  -EFAULT;
-		goto error_free_data_cpy;
-	}
-	/* In clever ring buffer designs this may not need to be freed.
-	 * When such a design exists I'll add this to ring access funcs.
-	 */
-	kfree(data);
-
-	return copied;
-
-error_free_data_cpy:
-	kfree(data);
-error_ret:
 	return ret;
 }
 

drivers/staging/iio/ring_generic.h

@@ -73,7 +73,7 @@ struct iio_ring_access_funcs {
 	int (*read_last)(struct iio_ring_buffer *ring, u8 *data);
 	int (*rip_lots)(struct iio_ring_buffer *ring,
 			size_t count,
-			u8 **data,
+			char __user *buf,
 			int *dead_offset);
 
 	int (*mark_param_change)(struct iio_ring_buffer *ring);

drivers/staging/iio/ring_sw.c

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/workqueue.h>
+#include <linux/poll.h>
 #include "ring_sw.h"
 #include "trigger.h"
 
@@ -152,11 +153,12 @@ static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
 }
 
 int iio_rip_sw_rb(struct iio_ring_buffer *r,
-		  size_t count, u8 **data, int *dead_offset)
+		  size_t count, char __user *buf, 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;
+	u8 *data;
 	int ret, max_copied;
 	int bytes_to_rip;
 
@@ -174,8 +176,8 @@ int iio_rip_sw_rb(struct iio_ring_buffer *r,
 	/* Limit size to whole of ring buffer */
 	bytes_to_rip = min((size_t)(ring->buf.bytes_per_datum*ring->buf.length), count);
 
-	*data = kmalloc(bytes_to_rip, GFP_KERNEL);
-	if (*data == NULL) {
+	data = kmalloc(bytes_to_rip, GFP_KERNEL);
+	if (data == NULL) {
 		ret = -ENOMEM;
 		goto error_ret;
 	}
@@ -204,30 +206,30 @@ int iio_rip_sw_rb(struct iio_ring_buffer *r,
 	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);
+		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);
+		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.bytes_per_datum - initial_read_p;
-		memcpy(*data, initial_read_p, max_copied);
+		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,
+			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,
+			memcpy(data + max_copied, ring->data,
 			       initial_write_p - ring->data);
 			max_copied += initial_write_p - ring->data;
 			end_read_p = initial_write_p;
@@ -264,11 +266,16 @@ int iio_rip_sw_rb(struct iio_ring_buffer *r,
 	while (ring->read_p != end_read_p)
 		ring->read_p = end_read_p;
 
-	return max_copied - *dead_offset;
+	ret = max_copied - *dead_offset;
 
+	if (copy_to_user(buf, data + *dead_offset, ret))  {
+		ret =  -EFAULT;
+		goto error_free_data_cpy;
+	}
 error_free_data_cpy:
-	kfree(*data);
+	kfree(data);
 error_ret:
+
 	return ret;
 }
 EXPORT_SYMBOL(iio_rip_sw_rb);

drivers/staging/iio/ring_sw.h

@@ -96,13 +96,13 @@ int iio_store_to_sw_rb(struct iio_ring_buffer *r, u8 *data, s64 timestamp);
  * iio_rip_sw_rb() - attempt to read data from the ring buffer
  * @r:			ring buffer instance
  * @count:		number of datum's to try and read
- * @data:		where the data will be stored.
+ * @buf:		userspace buffer into which data is copied
  * @dead_offset:	how much of the stored data was possibly invalidated by
  *			the end of the copy.
  **/
 int iio_rip_sw_rb(struct iio_ring_buffer *r,
 		  size_t count,
-		  u8 **data,
+		  char __user *buf,
 		  int *dead_offset);
 
 /**