Commit 423b24c3 authored Jul 23, 2015 by Ian Abbott Committed by Greg Kroah-Hartman Jul 24, 2015

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).

Fixes: b986be85 ("staging: comedi: usbduxsigma: tidy up analog input command support)
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: Bernd Porr <mail@berndporr.me.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: <stable@vger.kernel.org> # 3.19 onwards
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ab743598

drivers/staging/comedi/drivers/usbduxsigma.c

+16 −21

Original line number	Diff line number	Diff line
		@@ -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]);

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