staging: comedi: me4000: remove 'board' from me4000_ai_check_chanlist()

The maximum differential channel is half the subdevice 'n_chan'. Use
that instead and remove the need for the 'board' variable.

Also, the comedi core does no validate the aref flags. Add a check
to ensure that the subdevice actually supports the AREF_DIFF mode.

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/me4000.c b/drivers/staging/comedi/drivers/me4000.c
index 335fafc73a94d2443406044d07e2f948a6fd1a4a..008929e8d3fe8a85f43a7c476207942db613004d 100644 (file)
--- a/drivers/staging/comedi/drivers/me4000.c
+++ b/drivers/staging/comedi/drivers/me4000.c
@@ -568,8 +568,6 @@ static int me4000_ai_check_chanlist(struct comedi_device *dev,
                                    struct comedi_subdevice *s,
                                    struct comedi_cmd *cmd)
 {
-       const struct me4000_board *board = dev->board_ptr;
-       unsigned int max_diff_chan = board->ai_diff_nchan;
        unsigned int aref0 = CR_AREF(cmd->chanlist[0]);
        int i;
 
@@ -585,7 +583,13 @@ static int me4000_ai_check_chanlist(struct comedi_device *dev,
                }
 
                if (aref == AREF_DIFF) {
-                       if (chan >= max_diff_chan) {
+                       if (!(s->subdev_flags && SDF_DIFF)) {
+                               dev_err(dev->class_dev,
+                                       "Differential inputs are not available\n");
+                               return -EINVAL;
+                       }
+
+                       if (chan >= (s->n_chan / 2)) {
                                dev_dbg(dev->class_dev,
                                        "Channel number to high\n");
                                return -EINVAL;