Re: [PATCH] fbdev: suppress warning when assigning vga-save/restorebase

From: H. Peter Anvin
Date: Mon Aug 05 2013 - 17:14:29 EST

On 08/05/2013 02:02 PM, H. Peter Anvin wrote:
> On 08/05/2013 01:29 PM, Ondrej Zajicek wrote:
>> How this could even work? AFAIK these cards have to be explicitly programmed
>> to enable MMIO (which was not done in the patches). These patches claim that
>> it is for multi-domain PCI. I would guess that vgabase is NULL in common
>> configurations but if it is non-NULL, it probably wouldn't work, unless
>> there is some hardware magic that transparently converts MMIO (from CPU PoV)
>> to port IO (from card/PCI PoV).
> They presumably use iowrite/ioread, which use either I/O instructions or
> memory instructions depending on the address.

So the confusion really is in the iowrite interface, which can take
either a physical port address or a virtual memory address...


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