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Subject[PATCH 3.16.y-ckt 012/133] staging: comedi: usbduxsigma: don't clobber ai_timer in command test
Date
3.16.7-ckt18 -stable review patch.  If anyone has any objections, please let me know.

------------------

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()`.

** This backported patch also moves the code that sets up
`devpriv->ai_sample_count` from `usbduxsigma_ai_cmdtest()` to
`usbduxsigma_ai_cmd()` for the same reason as above. (This was not
needed in the upstream commit.) **

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>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
drivers/staging/comedi/drivers/usbduxsigma.c | 53 +++++++++++++---------------
1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
index ccc3ef7ba55c..e2c0c54e0910 100644
--- a/drivers/staging/comedi/drivers/usbduxsigma.c
+++ b/drivers/staging/comedi/drivers/usbduxsigma.c
@@ -572,35 +572,6 @@ 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 (cmd->stop_src == TRIG_COUNT) {
- /* data arrives as one packet */
- devpriv->ai_sample_count = cmd->stop_arg;
- } else {
- /* continuous acquisition */
- devpriv->ai_sample_count = 0;
- }
-
- if (err)
- return 4;
-
return 0;
}

@@ -700,6 +671,30 @@ static int usbduxsigma_ai_cmd(struct comedi_device *dev,

/* set current channel of the running acquisition to zero */
s->async->cur_chan = 0;
+
+ 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;
+ }
+ if (cmd->stop_src == TRIG_COUNT) {
+ /* data arrives as one packet */
+ devpriv->ai_sample_count = cmd->stop_arg;
+ } else {
+ /* continuous acquisition */
+ devpriv->ai_sample_count = 0;
+ }
+
for (i = 0; i < len; i++) {
unsigned int chan = CR_CHAN(cmd->chanlist[i]);


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