[PATCH] ide: explain the PCI bus test we do in <asm-i386/ide.h>
Matthew Wilcox asked that this got a comment explaining why it is done
so here it is.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/include/asm-i386/ide.h b/include/asm-i386/ide.h
index 79dfab8..4544401 100644
--- a/include/asm-i386/ide.h
+++ b/include/asm-i386/ide.h
@@ -41,6 +41,12 @@
static __inline__ unsigned long ide_default_io_base(int index)
{
+ /*
+ * If PCI is present then it is not safe to poke around
+ * the other legacy IDE ports. Only 0x1f0 and 0x170 are
+ * defined compatibility mode ports for PCI. A user can
+ * override this using ide= but we must default safe.
+ */
if (pci_find_device(PCI_ANY_ID, PCI_ANY_ID, NULL) == NULL) {
switch(index) {
case 2: return 0x1e8;