staging: comedi: cb_pcidio: fix for newer PCI-DIO48H

commit 0283f7a1 upstream.

At some point, Measurement Computing / ComputerBoards redesigned the
PCI-DIO48H to use a PLX PCI interface chip instead of an AMCC chip.
This meant they had to put their hardware registers in the PCI BAR 2
region instead of PCI BAR 1.  Unfortunately, they kept the same PCI
device ID for the new design.  This means the driver recognizes the
newer cards, but doesn't work (and is likely to screw up the local
configuration registers of the PLX chip) because it's using the wrong
region.

Since all the supported boards have the DIO registers in the PCI BAR 2
region except for older PCI-DIO48H boards which have an empty PCI BAR 2
region and the DIO registers in PCI BAR 1, determine which PCI BAR
region to use based on whether the PCI BAR 2 region is empty or not.

This change makes the `dioregs_badrindex` member of `struct
pcidio_board` redundant.  The `pcicontroler_badrindex` member is also
unused, so remove both members.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Cc: kernel-team@lists.ubuntu.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/staging/comedi/drivers/cb_pcidio.c

@@ -56,10 +56,6 @@ struct pcidio_board {
 	const char *name;	/*  name of the board */
 	int dev_id;
 	int n_8255;		/*  number of 8255 chips on board */
-
-	/*  indices of base address regions */
-	int pcicontroler_badrindex;
-	int dioregs_badrindex;
 };
 
 static const struct pcidio_board pcidio_boards[] = {
@@ -67,22 +63,16 @@ static const struct pcidio_board pcidio_boards[] = {
 	 .name = "pci-dio24",
 	 .dev_id = 0x0028,
 	 .n_8255 = 1,
-	 .pcicontroler_badrindex = 1,
-	 .dioregs_badrindex = 2,
 	 },
 	{
 	 .name = "pci-dio24h",
 	 .dev_id = 0x0014,
 	 .n_8255 = 1,
-	 .pcicontroler_badrindex = 1,
-	 .dioregs_badrindex = 2,
 	 },
 	{
 	 .name = "pci-dio48h",
 	 .dev_id = 0x000b,
 	 .n_8255 = 2,
-	 .pcicontroler_badrindex = 0,
-	 .dioregs_badrindex = 1,
 	 },
 };
 
@@ -244,10 +234,15 @@ static int pcidio_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		    ("cb_pcidio: failed to enable PCI device and request regions\n");
 		return -EIO;
 	}
-	devpriv->dio_reg_base
-	    =
+	/*
+	 * Use PCI BAR 2 region if non-zero length, else use PCI BAR 1 region.
+	 * PCI BAR 1 is only used for older PCI-DIO48H boards.  At some point
+	 * the PCI-DIO48H was redesigned to use the same PCI interface chip
+	 * (and same PCI BAR region) as the other boards.
+	 */
+	devpriv->dio_reg_base =
 	    pci_resource_start(devpriv->pci_dev,
-			       pcidio_boards[index].dioregs_badrindex);
+			       (pci_resource_len(pcidev, 2) ? 2 : 1));
 
 /*
  * Allocate the subdevice structures.  alloc_subdevice() is a