Mapping Physical Memory without a Device?

[John Baldwin]

On 09-Jun-2003 cd_freebsd wrote:
> jmallett at freebsd.org writes
> 
>>> You may also want to consider pmap_map.  It depends on what your >>requirements are?
> 
> while Bruce M Simpson [bms at spc.org] writes
> 
>>>It's quite evil and not machine independent..avoid.
> 
> -Who is right? (I like Juli's answer and she has FreeBSD.org in her name :) ) 
> -Why is pmap_mapdev bad? 
> -What makes it machine dependent?
> -What is the difference between pmap_devmap and pmap_map?
> 
> My requirements would be to map some or all of the following memory areas that are not associated
> with any device I own:
> 1) BIOS & UMB ram (0xC0000-0xFFFFF)
> 2) VGA Video buffer (0xA0000-0xBFFFF)

The first 1 meg of memory is 1:1 mapped at KERNBASE.  IOW, you can
get to the BIOS at KERNBASE + 0xc0000.  That should cover these first
two items.

> 3) Video Frame buffer (0x????0000-0x????0000)

Since this is not real RAM but device memory, pmap_mapdev() is ok
for this.

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/