Commit 3abfa106 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman

staging: comedi: comedi_buf: clarify comedi_buf_read_free()

Reword the comment about the need for the smp_mb().

Clarify the check to make sure the number of bytes to free is not
more than the number of bytes allocated.
Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 034cbd17
...@@ -312,14 +312,19 @@ EXPORT_SYMBOL(comedi_buf_read_alloc); ...@@ -312,14 +312,19 @@ EXPORT_SYMBOL(comedi_buf_read_alloc);
/* transfers control of a chunk from reader to free buffer space */ /* transfers control of a chunk from reader to free buffer space */
unsigned comedi_buf_read_free(struct comedi_async *async, unsigned int nbytes) unsigned comedi_buf_read_free(struct comedi_async *async, unsigned int nbytes)
{ {
/* barrier insures data has been read out of unsigned int allocated;
* buffer before read count is incremented */
/*
* ensure data has been read out of buffer before
* the async read count is incremented
*/
smp_mb(); smp_mb();
if ((int)(async->buf_read_count + nbytes -
async->buf_read_alloc_count) > 0) { allocated = comedi_buf_read_n_allocated(async);
if (nbytes > allocated) {
dev_info(async->subdevice->device->class_dev, dev_info(async->subdevice->device->class_dev,
"attempted to read-free more bytes than have been read-allocated.\n"); "attempted to read-free more bytes than have been read-allocated.\n");
nbytes = async->buf_read_alloc_count - async->buf_read_count; nbytes = allocated;
} }
async->buf_read_count += nbytes; async->buf_read_count += nbytes;
async->buf_read_ptr += nbytes; async->buf_read_ptr += nbytes;
......
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