[OpenBIOS] [PATCH] pci: enable io/memory unconditionally

Laurent Vivier Laurent at Vivier.EU
Thu Dec 10 13:09:34 CET 2009


>On Thu, Dec 10, 2009 at 01:20:23AM +0100, Laurent Vivier wrote:
>> Le mercredi 09 décembre 2009 à 17:53 +0200, Michael S. Tsirkin a écrit :
>> > VGA adapters need to claim memory and i/o
>> > transactions even if they do not have any
>> > i/o or memory bars. E.g. PCI spec, page 297,
>> > gives an example of such a device:
>> > 
>> >     Programming interface 0000 0000b
>> >     VGA-compatible controller. Memory
>> >     addresses 0A 0000h through 0B
>> >     FFFFh. I/O addresses 3B0h to 3BBh
>> >     and 3C0h to 3DFh and all aliases of
>> >     these addresses.
>> > 
>> > While bios could check for these devices and special-case them, it is
>> > easier to fix this by enabling i/o and memory space unconditionally:
>> > devices that do not support it will just ignore this setting.
>> > 
>> > Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
>> 
>> Applied, but could you give me an use case where previous behavior
>> breaks something ?
>> 
>> Regards,
>> Laurent
>
>qemu uses openbios and implements cirrus vga emulation,
>which has this device class and no IO bars.

qemu-system-ppc doesn't support cirrus vga emulation (only vga emulation), moreover openbios is not able to manage cirrus vga card.

So why this modification is needed ?

(even if it is correct according to the specs, it's why I've applied it)

Regards,
Laurent
-- 
--------------------- Laurent at vivier.eu  ---------------------
"Tout ce qui est impossible reste à accomplir"    Jules Verne
"Things are only impossible until they're not" Jean-Luc Picard



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