Subject: Re: how to allocate physically contiguous memory?
To: None <, port-alpha@NetBSD.ORG>
From: Ross Harvey <>
List: port-alpha
Date: 05/07/1997 17:33:48
 > Andrew Gallatin writes:
 > ...allocating physically contiguous memory
 >> Jason R. Thorpe writes:
 >> Eventually, you will call bus_dmamem_alloc() with the appropriate
 >> constraints, and then bus_dmamem_map() to map it into kva space
 >> (or allow the driver's mmap entry point to call bus_dmamem_mmap() to
 >> map it into user space :-)
 >> ...but for now, you'll be calling vm_page_alloc_memory() and then
 >> a loop around pmap_enter() (note, I don't call it contig anything,
 >> since the API allows the caller to specifiy a maximum segment
 >> count...)

Yes, you really do want the coming bus_dmamem_alloc() and other busdma
stuff. But given that you use a "but for now" technique in the present,
you could just grab it off the top of ram using an alpha-specific
procedure and take advantage of the kernel superpage. It takes about
three lines of code and uses no system (pmap) resources. Go see:

	arch/alpha/alpha/machdep.c		file
		alpha_init()			function
			valloc()		macro

And put a couple of goto's in while you are at it to annoy the purists. :)
Ross Harvey		Avalon Computer Systems, Inc.