[igt-dev] [PATCH i-g-t 10/11] lib/kms: Convert pipe id flags for a vblank using crtc offset

[Jani Nikula]

On Wed, 15 Jul 2020, Arkadiusz Hiler <arkadiusz.hiler at intel.com> wrote:
> In KMS & i915 there are two thing that are called pipe:

...

> Is there any practical reason besides people wanting to have test
> results for pipe-c corresponding to Intel's hardware understanding of
> what pipe-c is?
>
> You may need to ELI5 that to me. I have very rudimentary understanding
> of this area and only learned about the multiple meanings of "pipe"
> while doing the review here :-)

Something I've been saying all along: If you call something a "pipe", it
*must* mean Intel hardware pipe. If you call something "crtc index", it
*must* mean the ABI crtc index. Don't mix the two. Don't implicitly
convert between the two (i.e. you need explicit conversion using the
IOCTL). Assume it's purely a coincidence that they've previously matched
1:1.

In this case, naming is everything, and proper naming leads to clarity
of the concepts and implementation.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Graphics Center