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

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`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: fb1ef622e7 ("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>
This commit is contained in:
Ian Abbott
2015-07-23 16:46:58 +01:00
committed by Greg Kroah-Hartman
parent 423b24c37d
commit c04a1f1780
1 changed files with 14 additions and 19 deletions
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33
drivers/staging/comedi/drivers/usbduxsigma.c
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@@ -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) {