staging: comedi: comedi_test: support scan_begin_src == TRIG_FOLLOW

It is quite common for COMEDI subdevices that support commands to
support setting `scan_begin_src` to `TRIG_FOLLOW`.  This means the next
scan begins once all conversions in the current scan are complete.
Support the following timing combinations for the AI subdevice:

  scan_begin_src == TRIG_TIMER && convert_src == TRIG_TIMER
  scan_begin_src == TRIG_TIMER && convert_src == TRIG_NOW
  scan_begin_src == TRIG_FOLLOW && convert_src == TRIG_TIMER

The actual scan period in microseconds is stored in the `scan_period`
member of the private data structure `struct waveform_private`.  An
`unsigned int` is still wide enough, because the conversion period is no
more than `UINT_MAX / 1000` microseconds and the number of conversions
is no more than 16 (`N_CHANS * 2`).

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index f011fbd2fd96f91095ef40be776ab6b549889a18..cc35bd645d1b0908caf6b7d327649b69b7eafdb4 100644 (file)
--- a/drivers/staging/comedi/drivers/comedi_test.c
+++ b/drivers/staging/comedi/drivers/comedi_test.c
@@ -239,7 +239,8 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
        /* Step 1 : check if triggers are trivially valid */
 
        err |= comedi_check_trigger_src(&cmd->start_src, TRIG_NOW);
-       err |= comedi_check_trigger_src(&cmd->scan_begin_src, TRIG_TIMER);
+       err |= comedi_check_trigger_src(&cmd->scan_begin_src,
+                                       TRIG_FOLLOW | TRIG_TIMER);
        err |= comedi_check_trigger_src(&cmd->convert_src,
                                        TRIG_NOW | TRIG_TIMER);
        err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
@@ -255,6 +256,9 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
 
        /* Step 2b : and mutually compatible */
 
+       if (cmd->scan_begin_src == TRIG_FOLLOW && cmd->convert_src == TRIG_NOW)
+               err |= -EINVAL;         /* scan period would be 0 */
+
        if (err)
                return 2;
 
@@ -262,11 +266,21 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
 
        err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);
 
-       if (cmd->convert_src == TRIG_NOW)
+       if (cmd->convert_src == TRIG_NOW) {
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
+       } else {        /* cmd->convert_src == TRIG_TIMER */
+               if (cmd->scan_begin_src == TRIG_FOLLOW) {
+                       err |= comedi_check_trigger_arg_min(&cmd->convert_arg,
+                                                           NSEC_PER_USEC);
+               }
+       }
 
-       err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
-                                           NSEC_PER_USEC);
+       if (cmd->scan_begin_src == TRIG_FOLLOW) {
+               err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, 0);
+       } else {        /* cmd->scan_begin_src == TRIG_TIMER */
+               err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
+                                                   NSEC_PER_USEC);
+       }
 
        err |= comedi_check_trigger_arg_min(&cmd->chanlist_len, 1);
        err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
@@ -274,7 +288,7 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
 
        if (cmd->stop_src == TRIG_COUNT)
                err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
-       else    /* TRIG_NONE */
+       else    /* cmd->stop_src == TRIG_NONE */
                err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);
 
        if (err)
@@ -288,22 +302,27 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
                arg = min(arg,
                          rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
                arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
-               /* limit convert_arg to keep scan_begin_arg in range */
-               limit = UINT_MAX / cmd->scan_end_arg;
-               limit = rounddown(limit, (unsigned int)NSEC_PER_SEC);
-               arg = min(arg, limit);
+               if (cmd->scan_begin_arg == TRIG_TIMER) {
+                       /* limit convert_arg to keep scan_begin_arg in range */
+                       limit = UINT_MAX / cmd->scan_end_arg;
+                       limit = rounddown(limit, (unsigned int)NSEC_PER_SEC);
+                       arg = min(arg, limit);
+               }
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);
        }
 
-       /* round scan_begin_arg to nearest microsecond */
-       arg = cmd->scan_begin_arg;
-       arg = min(arg, rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
-       arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
-       if (cmd->convert_src == TRIG_TIMER) {
-               /* but ensure scan_begin_arg is large enough */
-               arg = max(arg, cmd->convert_arg * cmd->scan_end_arg);
+       if (cmd->scan_begin_src == TRIG_TIMER) {
+               /* round scan_begin_arg to nearest microsecond */
+               arg = cmd->scan_begin_arg;
+               arg = min(arg,
+                         rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
+               arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
+               if (cmd->convert_src == TRIG_TIMER) {
+                       /* but ensure scan_begin_arg is large enough */
+                       arg = max(arg, cmd->convert_arg * cmd->scan_end_arg);
+               }
+               err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
        }
-       err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
 
        if (err)
                return 4;
@@ -323,13 +342,18 @@ static int waveform_ai_cmd(struct comedi_device *dev,
                return -1;
        }
 
-       devpriv->scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;
-
        if (cmd->convert_src == TRIG_NOW)
                devpriv->convert_period = 0;
-       else    /* TRIG_TIMER */
+       else            /* cmd->convert_src == TRIG_TIMER */
                devpriv->convert_period = cmd->convert_arg / NSEC_PER_USEC;
 
+       if (cmd->scan_begin_src == TRIG_FOLLOW) {
+               devpriv->scan_period = devpriv->convert_period *
+                                      cmd->scan_end_arg;
+       } else {        /* cmd->scan_begin_src == TRIG_TIMER */
+               devpriv->scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;
+       }
+
        devpriv->last = ktime_get();
        devpriv->usec_current =
                ((u32)ktime_to_us(devpriv->last)) % devpriv->usec_period;