/*	$OpenBSD: vmparam.h,v 1.4 2009/10/14 20:18:26 miod Exp $ */
/* public domain */
#ifndef _SGI_VMPARAM_H_
#define _SGI_VMPARAM_H_

#define	VM_PHYSSEG_MAX	32	/* Max number of physical memory segments */

/*
 * On Origin and Octane families, DMA to 32-bit PCI devices is restricted.
 *
 * Systems with physical memory after the 2GB boundary needs to ensure
 * memory which may used for DMA transfers is allocated from the low
 * memory range.
 *
 * Other systems, like the O2, do not have such a restriction, but can not
 * have more than 2GB of physical memory, so this doesn't affect them.
 */

#define	VM_NFREELIST		2
#define	VM_FREELIST_DMA32	1	/* memory suitable for 32-bit DMA */

#include <mips64/vmparam.h>

#endif	/* _SGI_VMPARAM_H_ */

/*	$OpenBSD: vmparam.h,v 1.3 2009/05/08 18:42:04 miod Exp $ */

#ifndef _SGI_VMPARAM_H_
#define _SGI_VMPARAM_H_

#define	VM_PHYSSEG_MAX	32	/* Max number of physical memory segments */

#define	VM_NFREELIST		2
#define	VM_FREELIST_DMA32	1	/* memory under 2GB suitable for DMA */

#include <mips64/vmparam.h>

#endif	/* _SGI_VMPARAM_H_ */

--- 
+++ 
@@ -1,12 +1,23 @@
-/*	$OpenBSD: vmparam.h,v 1.3 2009/05/08 18:42:04 miod Exp $ */
-
+/*	$OpenBSD: vmparam.h,v 1.4 2009/10/14 20:18:26 miod Exp $ */
+/* public domain */
 #ifndef _SGI_VMPARAM_H_
 #define _SGI_VMPARAM_H_
 
 #define	VM_PHYSSEG_MAX	32	/* Max number of physical memory segments */
 
+/*
+ * On Origin and Octane families, DMA to 32-bit PCI devices is restricted.
+ *
+ * Systems with physical memory after the 2GB boundary needs to ensure
+ * memory which may used for DMA transfers is allocated from the low
+ * memory range.
+ *
+ * Other systems, like the O2, do not have such a restriction, but can not
+ * have more than 2GB of physical memory, so this doesn't affect them.
+ */
+
 #define	VM_NFREELIST		2
-#define	VM_FREELIST_DMA32	1	/* memory under 2GB suitable for DMA */
+#define	VM_FREELIST_DMA32	1	/* memory suitable for 32-bit DMA */
 
 #include <mips64/vmparam.h>
 
Add some comments to explain why the DMA32 physseg is really 2**31 bytes
long. Prompted by deraadt@ long ago.
