diff options
| author | H Hartley Sweeten <hsweeten@visionengravers.com> | 2013-01-09 13:30:49 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-01-17 16:53:59 -0800 |
| commit | 034cbd17922a8b6c64b227360314167c15c1f031 (patch) | |
| tree | 91011a131484a8f13653f825801dc803d9b0451f /drivers/staging/comedi/comedi_buf.c | |
| parent | 43f9137df461f6365f76b46f404fd6775eab7d51 (diff) | |
staging: comedi: comedi_buf: clarify comedi_buf_read_alloc()
Clarify the check to make sure the number of bytes to allocate is
available.
Reword the comment about the need for the smp_rmb().
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging/comedi/comedi_buf.c')
| -rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 06dd544ec2c..971f7394a1f 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -291,14 +291,20 @@ EXPORT_SYMBOL(comedi_buf_read_n_available); /* allocates a chunk for the reader from filled (and munged) buffer space */ unsigned comedi_buf_read_alloc(struct comedi_async *async, unsigned nbytes) { - if ((int)(async->buf_read_alloc_count + nbytes - async->munge_count) > - 0) { - nbytes = async->munge_count - async->buf_read_alloc_count; - } + unsigned int available; + + available = async->munge_count - async->buf_read_alloc_count; + if (nbytes > available) + nbytes = available; + async->buf_read_alloc_count += nbytes; - /* barrier insures read of munge_count occurs before we actually read - data out of buffer */ + + /* + * ensure the async buffer 'counts' are read before we + * attempt to read data from the read-alloc'ed buffer space + */ smp_rmb(); + return nbytes; } EXPORT_SYMBOL(comedi_buf_read_alloc); |