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staging: comedi: comedi_buf: cleanup comedi_buf_munge()

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Refactor this function so there is a single return point and only
one BUG_ON check. The BUG_ON needs to be looked at to see if it
can be safely removed.

Clarify the test in the munge loop that checks for a block copy
that would extend pass the end of the prealloc_buf.

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

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>
This commit is contained in:
H Hartley Sweeten 2013-01-09 13:29:19 -07:00 committed by Greg Kroah-Hartman
parent 47181eab71
commit 8d4be66947
1 changed files with 40 additions and 32 deletions
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72
drivers/staging/comedi/comedi_buf.c
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@ -194,8 +194,10 @@ unsigned int comedi_buf_write_alloc(struct comedi_async *async,
}
EXPORT_SYMBOL(comedi_buf_write_alloc);
/* munging is applied to data by core as it passes between user
* and kernel space */
/*
* munging is applied to data by core as it passes between user
* and kernel space
*/
static unsigned int comedi_buf_munge(struct comedi_async *async,
unsigned int num_bytes)
{
@ -203,40 +205,46 @@ static unsigned int comedi_buf_munge(struct comedi_async *async,
unsigned int count = 0;
const unsigned num_sample_bytes = bytes_per_sample(s);
if (s->munge == NULL || (async->cmd.flags & CMDF_RAWDATA)) {
if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) {
async->munge_count += num_bytes;
BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);
return num_bytes;
}
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
while (count < num_bytes) {
int block_size;
count = num_bytes;
} else {
/* don't munge partial samples */
num_bytes -= num_bytes % num_sample_bytes;
while (count < num_bytes) {
int block_size = num_bytes - count;
unsigned int buf_end;
block_size = num_bytes - count;
if (block_size < 0) {
dev_warn(s->device->class_dev,
"%s: %s: bug! block_size is negative\n",
__FILE__, __func__);
break;
if (block_size < 0) {
dev_warn(s->device->class_dev,
"%s: %s: bug! block_size is negative\n",
__FILE__, __func__);
break;
}
buf_end = async->prealloc_bufsz - async->munge_ptr;
if (block_size > buf_end)
block_size = buf_end;
s->munge(s->device, s,
async->prealloc_buf + async->munge_ptr,
block_size, async->munge_chan);
/*
* ensure data is munged in buffer before the
* async buffer munge_count is incremented
*/
smp_wmb();
async->munge_chan += block_size / num_sample_bytes;
async->munge_chan %= async->cmd.chanlist_len;
async->munge_count += block_size;
async->munge_ptr += block_size;
async->munge_ptr %= async->prealloc_bufsz;
count += block_size;
}
if ((int)(async->munge_ptr + block_size -
async->prealloc_bufsz) > 0)
block_size = async->prealloc_bufsz - async->munge_ptr;
s->munge(s->device, s, async->prealloc_buf + async->munge_ptr,
block_size, async->munge_chan);
smp_wmb(); /* barrier insures data is munged in buffer
* before munge_count is incremented */
async->munge_chan += block_size / num_sample_bytes;
async->munge_chan %= async->cmd.chanlist_len;
async->munge_count += block_size;
async->munge_ptr += block_size;
async->munge_ptr %= async->prealloc_bufsz;
count += block_size;
}
BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);
return count;
}