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: b986be8527c7 ("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>

diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
index 51846ad..2d68474 100644 (file)
--- a/drivers/staging/comedi/drivers/usbduxsigma.c
+++ b/drivers/staging/comedi/drivers/usbduxsigma.c
@@ -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]);