Commit e4317ce8 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman

staging: comedi: s626: fix continuous acquisition

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.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 27ca0391
......@@ -1483,7 +1483,7 @@ 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;
}
......
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