Commit c04a1f17 authored Jul 23, 2015 by Ian Abbott Committed by Greg Kroah-Hartman Jul 24, 2015

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



`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.

Fixes: fb1ef622 ("staging: comedi: usbduxsigma: tidy up analog output 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 423b24c3

drivers/staging/comedi/drivers/usbduxsigma.c

+14 −19

Original line number	Diff line number	Diff line
		@@ -914,25 +914,6 @@ static int usbduxsigma_ao_cmdtest(struct comedi_device *dev,
		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;
		}

		@@ -945,6 +926,20 @@ static int usbduxsigma_ao_cmd(struct comedi_device *dev,

		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) {

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