Skip to contentSkip to conversation

iio:kfifo_buf Take advantage of the fixed record size used in IIO

PATCH New Jonathan Cameron 1 participant 1 message May 28, 2012 IIO

lore
Share & tools
lore

Jonathan Cameron

author maintainer
#0 lore raw

PATCH v2 1/1 iio:kfifo_buf Take advantage of the fixed record size used in IIO

Sorry all, forgot to up the version number of the patch.

By bypassing the standard macros for setting up the kfifo we can take advantage of the fixed record size implementation without having to have a type to pass in (from which the size of an element is normally established).

In IIO we have variable 'scans' as our records in which any element can be present or not. They do not however vary when we are actually filling or reading from the buffer. Thus we have a fixed record size whenever we are actually running. As setup and tear down are not in the fast path we can take the overhead of reinitializing the kfifo every time.

This is an RFC as

a) I'm far from sure I got it right. (I didn't first time round)
b) There is probably a better way of doing it!

Signed-off-by Jonathan Cameron <[email protected]>
---
 drivers/iio/kfifo_buf.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)
drivers/iio/kfifo_buf.c +8 -5
index 6bf9d05..6ec763f 100644
@@ -22,7 +22,8 @@ static inline int __iio_allocate_kfifo(struct iio_kfifo *buf,
 		return -EINVAL;
 
 	__iio_update_buffer(&buf->buffer, bytes_per_datum, length);
-	return kfifo_alloc(&buf->kf, bytes_per_datum*length, GFP_KERNEL);
+	return __kfifo_alloc((struct __kfifo *)&buf->kf, length,
+			     bytes_per_datum, GFP_KERNEL);
 }
 
 static int iio_request_update_kfifo(struct iio_buffer *r)

@@ -94,9 +95,10 @@ static int iio_store_to_kfifo(struct iio_buffer *r,
 {
 	int ret;
 	struct iio_kfifo *kf = iio_to_kfifo(r);
-	ret = kfifo_in(&kf->kf, data, r->bytes_per_datum);
-	if (ret != r->bytes_per_datum)
+	ret = kfifo_in(&kf->kf, data, 1);
+	if (ret != 1)
 		return -EBUSY;
+
 	return 0;
 }
 

@@ -106,11 +108,12 @@ static int iio_read_first_n_kfifo(struct iio_buffer *r,
 	int ret, copied;
 	struct iio_kfifo *kf = iio_to_kfifo(r);
 
-	if (n < r->bytes_per_datum)
+	if (n < r->bytes_per_datum || r->bytes_per_datum == 0)
 		return -EINVAL;
 
-	n = rounddown(n, r->bytes_per_datum);
 	ret = kfifo_to_user(&kf->kf, buf, n, &copied);
+	if (ret < 0)
+		return ret;
 
 	return copied;
 }
Signature · 1 line
1.7.10.2