staging: comedi: s626: fix continuous acquisition
Ian Abbott [Fri, 22 Mar 2013 15:16:29 +0000 (15:16 +0000)]
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

index c72128f..42cad5c 100644 (file)
@@ -1882,7 +1882,7 @@ static int s626_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
        case TRIG_NONE:
                /*  continous acquisition */
                devpriv->ai_continous = 1;
-               devpriv->ai_sample_count = 0;
+               devpriv->ai_sample_count = 1;
                break;
        }