From mint-bounce@lists.fishpool.fi  Wed Dec  9 11:03:35 2009
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Message-ID: <4B1FC96F.1010306@freesbee.fr>
Date: Wed, 09 Dec 2009 16:59:43 +0100
From: =?ISO-8859-1?Q?Vincent_Rivi=E8re?= <vincent.riviere@freesbee.fr>
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To: mint <mint@lists.fishpool.fi>
Subject: Re: [MiNT] XaAES sources for FreeMiNT 1.16.3
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Johan Klockars wrote:
> IMO, it should never be possible for a user program/library to write
> directly to video memory.

If it is technically possible, like on ST, why not allowing this ? If
this is hidden under a clean API, there is nothing wrong.

> Drivers for graphics accelerators will need to access hardware
> registers

Some hardware registers are accessible in user mode. We have discovered
this recently with EtherNAT.

> and, unless I'm mistaken, the NatFeat instructions necessary
> for accelerated graphics under ARAnyM do not work in user mode.

ARAnyM can be modified to be more efficient.

However I agree, most drivers have to access supervisor mode to do their
work.

> You also need to consider that the VDI would sometimes be really
> unhappy if called from multiple contexts at once. So, you'd need
> kernel based locking for at least some things.

Sure, the VDI has to use some mutex or similar. So the VDI has to call
the kernel, as every user program.

-- 
Vincent Rivière