staging: comedi: das1800: cleanup das1800_probe()

Make this function return a pointer to the boardinfo instead of an index.
Since it's not typical, add a comment to clarify why this legacy driver
does a probe.

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/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index 53baf37cd21a6ab71e6eea8bb66a524e51f8e24e..a7471bb7c39bf019710409832f2f840c68084361 100644 (file)
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -1216,62 +1216,67 @@ static void das1800_free_dma(struct comedi_device *dev)
                comedi_isadma_free(devpriv->dma);
 }
 
-static int das1800_probe(struct comedi_device *dev)
+static const struct das1800_board *das1800_probe(struct comedi_device *dev)
 {
        const struct das1800_board *board = dev->board_ptr;
-       int index;
+       int index = board ? board - das1800_boards : -EINVAL;
        int id;
 
-       /* calc the offset to the boardinfo that was found by the core */
-       index = board - das1800_boards;
-
-       /* verify that the board id matches the boardinfo */
+       /*
+        * The dev->board_ptr will be set by comedi_device_attach() if the
+        * board name provided by the user matches a board->name in this
+        * driver. If so, this function sanity checks the id to verify that
+        * the board is correct.
+        *
+        * If the dev->board_ptr is not set, the user is trying to attach
+        * an unspecified board to this driver. In this case the id is used
+        * to 'probe' for the correct dev->board_ptr.
+        */
        id = (inb(dev->iobase + DAS1800_DIGITAL) >> 4) & 0xf;
        switch (id) {
        case 0x3:
                if (index == das1801st_da || index == das1802st_da ||
                    index == das1701st_da || index == das1702st_da)
-                       return index;
+                       return board;
                index = das1801st;
                break;
        case 0x4:
                if (index == das1802hr_da || index == das1702hr_da)
-                       return index;
+                       return board;
                index = das1802hr;
                break;
        case 0x5:
                if (index == das1801ao || index == das1802ao ||
                    index == das1701ao || index == das1702ao)
-                       return index;
+                       return board;
                index = das1801ao;
                break;
        case 0x6:
                if (index == das1802hr || index == das1702hr)
-                       return index;
+                       return board;
                index = das1802hr;
                break;
        case 0x7:
                if (index == das1801st || index == das1802st ||
                    index == das1701st || index == das1702st)
-                       return index;
+                       return board;
                index = das1801st;
                break;
        case 0x8:
                if (index == das1801hc || index == das1802hc)
-                       return index;
+                       return board;
                index = das1801hc;
-               break;
        default:
                dev_err(dev->class_dev,
                        "Board model: probe returned 0x%x (unknown, please report)\n",
                        id);
-               break;
+               return NULL;
        }
        dev_err(dev->class_dev,
                "Board model (probed, not recommended): %s series\n",
                das1800_boards[index].name);
 
-       return index;
+       return &das1800_boards[index];
 }
 
 static int das1800_attach(struct comedi_device *dev,
@@ -1281,7 +1286,6 @@ static int das1800_attach(struct comedi_device *dev,
        struct das1800_private *devpriv;
        struct comedi_subdevice *s;
        unsigned int irq = it->options[1];
-       int board;
        int ret;
 
        devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
@@ -1292,14 +1296,12 @@ static int das1800_attach(struct comedi_device *dev,
        if (ret)
                return ret;
 
-       board = das1800_probe(dev);
-       if (board < 0) {
+       thisboard = das1800_probe(dev);
+       if (!thisboard) {
                dev_err(dev->class_dev, "unable to determine board type\n");
                return -ENODEV;
        }
-
-       dev->board_ptr = das1800_boards + board;
-       thisboard = dev->board_ptr;
+       dev->board_ptr = thisboard;
        dev->board_name = thisboard->name;
 
        /*  if it is an 'ao' board with fancy analog out then we need extra io ports */