[ 3.5.y.z extended stable ] Patch "staging: comedi: s626: fix continuous acquisition" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    staging: comedi: s626: fix continuous acquisition

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 48467539d71e1dabca1ab26855dfbaf35f061284 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Fri, 22 Mar 2013 15:16:29 +0000
Subject: [PATCH] staging: comedi: s626: fix continuous acquisition

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 at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/comedi/drivers/s626.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/s626.c b/drivers/staging/comedi/drivers/s626.c
index e68e474..9c6b758 100644
--- a/drivers/staging/comedi/drivers/s626.c
+++ b/drivers/staging/comedi/drivers/s626.c
@@ -1823,7 +1823,7 @@ 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;
 	}

--
1.8.1.2