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Date: Tue, 15 Feb 2005 15:05:20 -0500 (EST)
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Subject: mapping small parts of a pci card to conserve KVA
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I maintain drivers for a PCI card which presents itself as having
16MB of address space.  Eg:

mx0: <Myrinet PCIXE> mem 0xf9000000-0xf9ffffff irq 20 at device 3.0 on pci1

However, most of that address space does not need to be mapped into
the host.  Really, only a little over 2MB needs to be mapped (3 regions
with length 1024 bytes, 256 bytes, and 2MB).

I've tried to re-write things so that I make multiple calls
to bus_alloc_resource() with the (hopefully) appropriate offset and
lengths.  Eg:

  rid = PCIR_MAPS;
  *res = bus_alloc_resource(is->arch.dev, SYS_RES_MEMORY, &rid,
	     (u_long)offset, 
 	     (u_long)(offset + len - 1), len, 
             RF_ACTIVE|PCI_RF_DENSE);

At least on 5.3R, I seem to get back the same struct resource * from
each call.  rman_get_virtual() returns a different kva for each
mapping, yet they all seem to map to the same physical address. 
Eg, I call vtophys() on the results of rman_get_virtual(),
for each segment, and they all map to 0xf9000000.

Is there a way to just map what I need?

Thanks,

Drew