[PATCH 4.1 026/102] staging: comedi: usbduxsigma: dont clobber ai_timer in command test

Greg Kroah-Hartman
2015-09-19T17:38:51Z

From: Ian Abbott <abbotti@mev.co.uk>

commit 423b24c37dd5794a674c74b0ed56392003a69891 upstream.

`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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/comedi/drivers/usbduxsigma.c | 37 +++++++++++----------------
1 file changed, 16 insertions(+), 21 deletions(-)

--- a/drivers/staging/comedi/drivers/usbduxsigma.c
+++ b/drivers/staging/comedi/drivers/usbduxsigma.c
@@ -550,27 +550,6 @@ static int usbduxsigma_ai_cmdtest(struct
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;
}

@@ -668,6 +647,22 @@ static int usbduxsigma_ai_cmd(struct com

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]);