staging: comedi: ni_labpc: clarify the cmd->start_arg validation

This driver supports cmd->start_src sources of TRIG_NOW and TRIG_EXT.
Refactor the (*do_cmdtest) to clarify the trivial validation of the
cmd->start_arg.

This also fixes a bug, the cmd->start_src has the trigger not the
cmd->start_arg.

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

diff --git a/drivers/staging/comedi/drivers/ni_labpc.c b/drivers/staging/comedi/drivers/ni_labpc.c
index f80ca32783143657e06cb14b3ccfccec80fa512c..fc9d31420956ffdd278eb5a864836efc4cb775ea 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_labpc.c
+++ b/drivers/staging/comedi/drivers/ni_labpc.c
@@ -649,8 +649,14 @@ static int labpc_ai_cmdtest(struct comedi_device *dev,
 
        /* Step 3: check if arguments are trivially valid */
 
-       if (cmd->start_arg == TRIG_NOW)
+       switch (cmd->start_src) {
+       case TRIG_NOW:
                err |= cfc_check_trigger_arg_is(&cmd->start_arg, 0);
+               break;
+       case TRIG_EXT:
+               /* start_arg value is ignored */
+               break;
+       }
 
        if (!cmd->chanlist_len)
                err |= -EINVAL;