IB/mthca: Schedule MSI support for removal

The mthca driver supports both MSI and MSI-X.  However, MSI-X works with
all hardware that the driver handles, and provides a superset of what
MSI does, so there's no point in having code for both.  Schedule MSI
support for removal in 2008 to give anyone who actually needs MSI and
who can't use MSI time to speak up.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

Documentation/feature-removal-schedule.txt

@@ -310,3 +310,13 @@ Why:  The arch/powerpc tree is the merged architecture for ppc32 and ppc64
 Who:  linuxppc-dev@ozlabs.org
 
 ---------------------------
+
+What:	mthca driver's MSI support
+When:	January 2008
+Files:	drivers/infiniband/hw/mthca/*.[ch]
+Why:	All mthca hardware also supports MSI-X, which provides
+	strictly more functionality than MSI.  So there is no point in
+	having both MSI-X and MSI support in the driver.
+Who:	Roland Dreier <rolandd@cisco.com>
+
+---------------------------

drivers/infiniband/hw/mthca/mthca_main.c

@@ -67,7 +67,7 @@ MODULE_PARM_DESC(msi_x, "attempt to use MSI-X if nonzero");
 
 static int msi = 0;
 module_param(msi, int, 0444);
-MODULE_PARM_DESC(msi, "attempt to use MSI if nonzero");
+MODULE_PARM_DESC(msi, "attempt to use MSI if nonzero (deprecated, use MSI-X instead)");
 
 #else /* CONFIG_PCI_MSI */
 
@@ -1117,9 +1117,21 @@ static int __mthca_init_one(struct pci_dev *pdev, int hca_type)
 
 	if (msi_x && !mthca_enable_msi_x(mdev))
 		mdev->mthca_flags |= MTHCA_FLAG_MSI_X;
-	if (msi && !(mdev->mthca_flags & MTHCA_FLAG_MSI_X) &&
-	    !pci_enable_msi(pdev))
-		mdev->mthca_flags |= MTHCA_FLAG_MSI;
+	else if (msi) {
+		static int warned;
+
+		if (!warned) {
+			printk(KERN_WARNING PFX "WARNING: MSI support will be "
+			       "removed from the ib_mthca driver in January 2008.\n");
+			printk(KERN_WARNING "    If you are using MSI and cannot "
+			       "switch to MSI-X, please tell "
+			       "<general@lists.openfabrics.org>.\n");
+			++warned;
+		}
+
+		if (!pci_enable_msi(pdev))
+			mdev->mthca_flags |= MTHCA_FLAG_MSI;
+	}
 
 	if (mthca_cmd_init(mdev)) {
 		mthca_err(mdev, "Failed to init command interface, aborting.\n");