[okl4-developer] Starting with graphic output

[Geoffrey Lee]

On Tue, May 06, 2008 at 12:10:50PM +0000, Remy Gottschalk wrote:

Hi Remy

What you have done seems to be correct.  The zero = False needs to be
there.  What is built is called a "direct" memsection section, i.e.
the virtual address has a one to one correspondence with the physical
address.  When you zero it does it using the virtual address.  0xf0000000 
not accessible because that is where the kernel is typically mapped.

The only thing I see wrong is the memory is mapped as default memory.  
You probably want uncached instead.  (note the vga mapping of default
is probably wrong, I'll tag it in the bug database if necessary.) 

Hope that helps.

	-gl



> 
> Since it was mostly done by instinct could you confirm (or correct of
> course) that I have understood of the process.
> 
> All those modification end end up in weaver.xml and thus change the
> image built and the behavior of iguana letting it know a specific memory
> region will be used in a special way.
> 
> What was done in platform/pc99/tools/machines.py correspond to
> <physical_memory name="fb">
> 			<region base="0xf0000000" size="0x2001000" type="dedicated" />
> in the machine section of weaver.xml and only declare the region.
> 
> What was done in projects/iguana/SConstruct correspond to 
> <memsection name="fb" size="0x2001000" virt_addr="0xf0000000"
> physpool="fb" zero="false" cache_policy="default" />
> and link OKLinux to the region defined informing iguana that it has the
> right to access it, the mapping to do and some attributes.
> 
> Last thing that bothers me a little, compared to the VGA memory I had to
> add the zero = False to avoid a roottask pagefault at initialization
> time. (ie roottask write pagefault at f0000000, ip=090035dc - deny) I
> "felt" that it was the thing to do but don't clearly understand what it
> involves. I seems pretty clear that it disable a "zeroing" at
> initialization but why has it to be done ? and is it right and secure to
> do so ?
> 
> Regards,
> 
> -- 
> Remy Gottschalk - rgottschalk at linagora.com
> Ingénieur informatique embarquée
> Groupe LINAGORA - http://www.linagora.com
> Tél.: +33(0)1 58 18 68 28 - Fax : +33(0)1 58 18 68 29
> 
> 

--