On 15/02/18 20:13, Frank Mori Hess wrote:
A rounding error was causing comedi_nsamples_left to
return the wrong value when nsamples was not a multiple
of the scan length.
Cc: <stable@xxxxxxxxxxxxxxx> # v4.4+
Signed-off-by: Frank Mori Hess <fmh6jj@xxxxxxxxx>
---
drivers/staging/comedi/drivers.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 0b43db6371c6..c11c22bd6d13 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -484,8 +484,7 @@ unsigned int comedi_nsamples_left(struct comedi_subdevice *s,
struct comedi_cmd *cmd = &async->cmd;
if (cmd->stop_src == TRIG_COUNT) {
- unsigned int nscans = nsamples / cmd->scan_end_arg;
- unsigned int scans_left = __comedi_nscans_left(s, nscans);
+ unsigned int scans_left = __comedi_nscans_left(s, cmd->stop_arg);
unsigned int scan_pos =
comedi_bytes_to_samples(s, async->scan_progress);
unsigned long long samples_left = 0;
I think Hartley's original implementation of comedi_nsamples_left() in
commit f615915ee5fa ("staging: comedi: drivers: introduce
comedi_nsamples_left()") may have also avoided the problem by adding 1
to nscans:
/* +1 to force comedi_nscans_left() to return the scans left */
unsigned int nscans = (nsamples / cmd->scan_end_arg) + 1;
except for an extreme case I attempted to fix in commit 92d354cbe95f
("staging: comedi: fix extreme case of comedi_nsamples_left()") where I
removed the "+ 1" amongst other changes. So I may have broke it.
Your fix should work though. Thanks!
Reviewed-by: Ian Abbott <abbotti@xxxxxxxxx>
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Web: http://www.mev.co.uk/ )=-
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