Re: [Qemu-devel] [PATCHv2 1/2] sun4m: Add Sun CG3 framebuffer and corresponding OpenBIOS FCode ROM

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

On 14/02/14 14:54, Peter Crosthwaite wrote:

>> The short answer is "we don't know" because we don't have any documentation.
>
> Sigh.... This has happened quite a lot lately.
>
> If the kernel driver has macros, re-use them as much as possible. If
> you have a vague idea on whats, what, a few well invented names would
> help the device self-documentation.

Okay. I now have a revised version which borrows macro names from the 
Linux and BSD drivers which I think should be more readable. I'll post 
the revised version to the list shortly.

>>> Your hander switch statements stride in 4, are you only doing this for
>>> your one exception case of that one-byte big-endian access I commented
>>> earlier.
>>
>>
>> Yes, that is correct.
>>
>
> Should you trap misaligned accesses then?

Over the weekend I found out that the non-BT458 accesses (addr >= 0x10) 
are done as byte accesses and so byte accesses do need to be allowed to 
these registers. My interpretation of reading the SBus documentation is 
that on real hardware the bus converts accesses for you, and so I don't 
think a trap would be suitable here. Also I've not found an image (yet) 
that attempts bad accesses in this way across my OpenBIOS ISO test suite...


ATB,

Mark.