From b03ee3d047cafd407896b4a2ad018338387ec8e7 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Tue, 19 Jul 2016 12:17:39 +0100 Subject: [PATCH] staging: comedi: ni_mio_common: fix AO inttrig backwards compatibility commit f0f4b0cc3a8cffd983f5940d46cd0227f3f5710a upstream. Commit ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the cmd->start_arg validation and use") introduced a backwards compatibility issue in the use of asynchronous commands on the AO subdevice when `start_src` is `TRIG_EXT`. Valid values for `start_src` are `TRIG_INT` (for internal, software trigger), and `TRIG_EXT` (for external trigger). When set to `TRIG_EXT`. In both cases, the driver relies on an internal, software trigger to set things up (allowing the user application to write sufficient samples to the data buffer before the trigger), so it acts as a software "pre-trigger" in the `TRIG_EXT` case. The software trigger is handled by `ni_ao_inttrig()`. Prior to the above change, when `start_src` was `TRIG_INT`, `start_arg` was required to be 0, and `ni_ao_inttrig()` checked that the software trigger number was also 0. After the above change, when `start_src` was `TRIG_INT`, any value was allowed for `start_arg`, and `ni_ao_inttrig()` checked that the software trigger number matched this `start_arg` value. The backwards compatibility issue is that the internal trigger number now has to match `start_arg` when `start_src` is `TRIG_EXT` when it previously had to be 0. Fix the backwards compatibility issue in `ni_ao_inttrig()` by always allowing software trigger number 0 when `start_src` is something other than `TRIG_INT`. Thanks to Spencer Olson for reporting the issue. Signed-off-by: Ian Abbott Reported-by: Spencer Olson Fixes: ebb657babfa9 ("staging: comedi: ni_mio_common: clarify the cmd->start_arg validation and use") Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/ni_mio_common.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c index 27fbf1a81097..955f802a1d0a 100644 --- a/drivers/staging/comedi/drivers/ni_mio_common.c +++ b/drivers/staging/comedi/drivers/ni_mio_common.c @@ -2823,7 +2823,15 @@ static int ni_ao_inttrig(struct comedi_device *dev, int i; static const int timeout = 1000; - if (trig_num != cmd->start_arg) + /* + * Require trig_num == cmd->start_arg when cmd->start_src == TRIG_INT. + * For backwards compatibility, also allow trig_num == 0 when + * cmd->start_src != TRIG_INT (i.e. when cmd->start_src == TRIG_EXT); + * in that case, the internal trigger is being used as a pre-trigger + * before the external trigger. + */ + if (!(trig_num == cmd->start_arg || + (trig_num == 0 && cmd->start_src != TRIG_INT))) return -EINVAL; /* Null trig at beginning prevent ao start trigger from executing more than -- 2.20.1