[ 08/68] staging: comedi: s626: fix continuous acquisition

Greg Kroah-Hartman
2013-04-02T22:14:15Z

From: Ian Abbott <abbotti@mev.co.uk>

commit e4317ce877a31dbb9d96375391c1c4ad2210d637 upstream.

For the s626 driver, there is a bug in the handling of asynchronous
commands on the AI subdevice when the stop source is `TRIG_NONE`. The
command should run continuously until cancelled, but the interrupt
handler stops the command running after the first scan.

The command set-up function `s626_ai_cmd()` contains this code:

switch (cmd->stop_src) {
case TRIG_COUNT:
/* data arrives as one packet */
devpriv->ai_sample_count = cmd->stop_arg;
devpriv->ai_continous = 0;
break;
case TRIG_NONE:
/* continous acquisition */
devpriv->ai_continous = 1;
devpriv->ai_sample_count = 0;
break;
}

The interrupt handler `s626_irq_handler()` contains this code:

if (!(devpriv->ai_continous))
devpriv->ai_sample_count--;
if (devpriv->ai_sample_count <= 0) {
devpriv->ai_cmd_running = 0;
/* ... */
}

So `devpriv->ai_sample_count` is only decremented for the `TRIG_COUNT`
case, but `devpriv->ai_cmd_running` is set to 0 (and the command
stopped) regardless.

Fix this in `s626_ai_cmd()` by setting `devpriv->ai_sample_count = 1`
for the `TRIG_NONE` case. The interrupt handler will not decrement it
so it will remain greater than 0 and the check for stopping the
acquisition will fail.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/comedi/drivers/s626.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/staging/comedi/drivers/s626.c
+++ b/drivers/staging/comedi/drivers/s626.c
@@ -1882,7 +1882,7 @@ static int s626_ai_cmd(struct comedi_dev
case TRIG_NONE:
/* continous acquisition */
devpriv->ai_continous = 1;
- devpriv->ai_sample_count = 0;
+ devpriv->ai_sample_count = 1;
break;
}