On 29/03/17 11:24, Laurent Pinchart wrote:
> On Wednesday 29 Mar 2017 11:23:00 Tomi Valkeinen wrote:
>> On 29/03/17 11:13, Laurent Pinchart wrote:
>>> Hi Tomi,
>>>
>>> Thank you for the patch.
>>>
>>> On Tuesday 28 Mar 2017 16:07:50 Tomi Valkeinen wrote:
>>>> mode_config's min_width and min_height are both set to 32, which is
>>>> overly restrictive.
>>>>
>>>> The real limits depend on whether we're configuring a crtc or a plane,
>>>> but a limit of 8x2 is safe for both cases.
>>>
>>> Strictly speaking it's planes in all cases, you could talk about primary
>>> or overlay planes instead. Apart from that,
>>
>> Hmm, well, on the HW they are different. We have CRTC limits, and we
>> have plane limits.
>>
>> In our HW, I think we can have 1x1 planes (at least with RGB). But CRTC
>> minimum depends on the display used. In some cases CRTC minimum is 1x1,
>> but usually it's 8x1 I think.
>>
>> And talking about primary or overlay planes is so legacy... With atomic,
>> we just have planes! =)
> 
> CRTCs and planes are KMS concepts, at the hardware level we have background 
> and overlay planes, don't we ?

No, on the HW level we have... I don't know what's the proper name, but
whatever matches the CRTC. The dss driver calls it overlay manager, but
that's a silly name too. It's the video timing generator, plus overlay
composition. It does have a default background color, though.

And then we have overlays, i.e. planes.

You can have the CRTC enabled without any planes. Then you'll see the
background color. If you have planes, they can be smaller than the CRTC.

 Tomi