[Mesa-dev] gallium: blitters and scissors

[Alex Deucher]

On Tue, Oct 12, 2010 at 11:50 PM, Corbin Simpson
<mostawesomedude at gmail.com> wrote:
> Yes, that particular part of the spec is fairly Poulsboriffic. Does any open
> hardware have a scissor enable/disable bit?

Most hardware can disable/enable cliprects, but not scissors.

Alex

>
> Sending from a mobile, pardon the brevity. ~ C.
>
> On Oct 12, 2010 8:47 PM, "Dave Airlie" <airlied at gmail.com> wrote:
>> On Wed, Oct 13, 2010 at 1:07 PM, Dave Airlie <airlied at gmail.com> wrote:
>>> On Wed, Oct 13, 2010 at 12:07 PM, Dave Airlie <airlied at gmail.com> wrote:
>>>> I've noticed that none of the blitters use scissor state, and wondered
>>>> if there was a reason for this.
>>>>
>>>> It looks like drivers are expected to setup scissor state in the
>>>> framebuffer setup and in the set scissor state, but with r600g due to
>>>> the underlying state tracking it can end up doing the wrong thing.
>>>>
>>>> The 3 patches add CSO cache + u_blit + u_blitter scissor usage.
>>>>
>>>> Just wondering if I'm violating some rules of the gallium interface or
>>>> not.
>>>
>>> I realised this was a quite deep hole I started digging in mesa/st,
>>> any advice on whether cleaning it up is a good idea?
>>>
>>
>> Okay so it helps to read the docs, since it the scissor state enable
>> relies on a bit in the rasterizer state.
>>
>> So it looks like we should always set scissor regs in the framebuffer
>> state and only modify them if we notice
>> the rasterizer bit is enabled.
>>
>> Dave.
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