patch "staging: comedi: usbduxsigma: don't clobber ai_timer in command test" added to staging-testing

This is a note to let you know that I've just added the patch titled

staging: comedi: usbduxsigma: don't clobber ai_timer in command test

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the staging-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From: Ian Abbott <[email protected]>
Date: Thu, 23 Jul 2015 16:46:57 +0100
Subject: staging: comedi: usbduxsigma: don't clobber ai_timer in command test

devpriv->ai_timer is used while an asynchronous command is running on the AI subdevice. It also gets modified by the subdevice's cmdtest handler for checking new asynchronous commands (usbduxsigma_ai_cmdtest()), which is not correct as it's allowed to check new commands while an old command is still running. Fix it by moving the code which sets up devpriv->ai_timer and devpriv->ai_interval into the subdevice's cmd handler, usbduxsigma_ai_cmd().

Note that the removed code in usbduxsigma_ai_cmdtest() checked that devpriv->ai_timer did not end up less than than 1, but that could not happen because cmd->scan_begin_arg had already been checked to be at least the minimum required value (at least when cmd->scan_begin_src == TRIG_TIMER, which had also been checked to be the case).

---
 drivers/staging/comedi/drivers/usbduxsigma.c | 37 ++++++++++++----------------
 1 file changed, 16 insertions(+), 21 deletions(-)

index 51846adf8340..2d684747a639 100644
@@ -551,27 +551,6 @@ static int usbduxsigma_ai_cmdtest(struct comedi_device *dev,
 	if (err)
 		return 3;
 
-	/* Step 4: fix up any arguments */
-
-	if (high_speed) {
-		/*
-		 * every 2 channels get a time window of 125us. Thus, if we
-		 * sample all 16 channels we need 1ms. If we sample only one
-		 * channel we need only 125us
-		 */
-		devpriv->ai_interval = interval;
-		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
-	} else {
-		/* interval always 1ms */
-		devpriv->ai_interval = 1;
-		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
-	}
-	if (devpriv->ai_timer < 1)
-		err |= -EINVAL;
-
-	if (err)
-		return 4;
-
 	return 0;
 }
 

@@ -669,6 +648,22 @@ static int usbduxsigma_ai_cmd(struct comedi_device *dev,
 
 	down(&devpriv->sem);
 
+	if (devpriv->high_speed) {
+		/*
+		 * every 2 channels get a time window of 125us. Thus, if we
+		 * sample all 16 channels we need 1ms. If we sample only one
+		 * channel we need only 125us
+		 */
+		unsigned int interval = usbduxsigma_chans_to_interval(len);
+
+		devpriv->ai_interval = interval;
+		devpriv->ai_timer = cmd->scan_begin_arg / (125000 * interval);
+	} else {
+		/* interval always 1ms */
+		devpriv->ai_interval = 1;
+		devpriv->ai_timer = cmd->scan_begin_arg / 1000000;
+	}
+
 	for (i = 0; i < len; i++) {
 		unsigned int chan  = CR_CHAN(cmd->chanlist[i]);
 

2.4.6