PATCH: Explain the PCI bus test we do in IDE

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

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>

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.14-rc4-mm1/include/asm-i386/ide.h linux-2.6.14-rc4-mm1/include/asm-i386/ide.h
--- linux.vanilla-2.6.14-rc4-mm1/include/asm-i386/ide.h	2005-10-20 16:10:12.000000000 +0100
+++ linux-2.6.14-rc4-mm1/include/asm-i386/ide.h	2005-10-20 16:37:20.000000000 +0100
@@ -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;

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