Patch "staging: comedi: usbduxsigma: don't clobber ao_timer in command test" has been added to the 4.1-stable tree

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

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

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
staging-comedi-usbduxsigma-don-t-clobber-ao_timer-in-command-test.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ian Abbott <[email protected]>
Date: Thu, 23 Jul 2015 16:46:58 +0100
Subject: staging: comedi: usbduxsigma: don't clobber ao_timer in command test

From: Ian Abbott <[email protected]>

commit c04a1f17803e0d3eeada586ca34a6b436959bc20 upstream.

devpriv->ao_timer is used while an asynchronous command is running on the AO subdevice. It also gets modified by the subdevice's cmdtest handler for checking new asynchronous commands, usbduxsigma_ao_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->ao_timer into the subdevice's cmd handler, usbduxsigma_ao_cmd().

Note that the removed code in usbduxsigma_ao_cmdtest() checked that devpriv->ao_timer did not end up less that 1, but that could not happen due because cmd->scan_begin_arg or cmd->convert_arg had already been range-checked.

Also note that we tested the high_speed variable in the old code, but that is currently always 0 and means that we always use "scan" timing (cmd->scan_begin_src == TRIG_TIMER and cmd->convert_src == TRIG_NOW) and never "convert" (individual sample) timing (cmd->scan_begin_src == TRIG_FOLLOW and cmd->convert_src == TRIG_TIMER). The moved code tests cmd->convert_src instead to decide whether "scan" or "convert" timing is being used, although currently only "scan" timing is supported.

---
 drivers/staging/comedi/drivers/usbduxsigma.c |   33 +++++++++++----------------
 1 file changed, 14 insertions(+), 19 deletions(-)

@@ -912,25 +912,6 @@ static int usbduxsigma_ao_cmdtest(struct
 	if (err)
 		return 3;
 
-	/* Step 4: fix up any arguments */
-
-	/* we count in timer steps */
-	if (high_speed) {
-		/* timing of the conversion itself: every 125 us */
-		devpriv->ao_timer = cmd->convert_arg / 125000;
-	} else {
-		/*
-		 * timing of the scan: every 1ms
-		 * we get all channels at once
-		 */
-		devpriv->ao_timer = cmd->scan_begin_arg / 1000000;
-	}
-	if (devpriv->ao_timer < 1)
-		err |= -EINVAL;
-
-	if (err)
-		return 4;
-
 	return 0;
 }
 

@@ -943,6 +924,20 @@ static int usbduxsigma_ao_cmd(struct com
 
 	down(&devpriv->sem);
 
+	if (cmd->convert_src == TRIG_TIMER) {
+		/*
+		 * timing of the conversion itself: every 125 us
+		 * at high speed (not used yet)
+		 */
+		devpriv->ao_timer = cmd->convert_arg / 125000;
+	} else {
+		/*
+		 * timing of the scan: every 1ms
+		 * we get all channels at once
+		 */
+		devpriv->ao_timer = cmd->scan_begin_arg / 1000000;
+	}
+
 	devpriv->ao_counter = devpriv->ao_timer;
 
 	if (cmd->start_src == TRIG_NOW) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/staging-comedi-usbduxsigma-don-t-clobber-ao_timer-in-command-test.patch queue-4.1/staging-comedi-adl_pci7x3x-fix-digital-output-on-pci-7230.patch queue-4.1/staging-comedi-usbduxsigma-don-t-clobber-ai_timer-in-command-test.patch