Re: [Patch 2/4] dt-bindings: display/ti: Add plane binding to dispc node

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

On 09/03/18 20:27, Benoit Parrot wrote:

>> Is logical plane a h/w concept?
> 
> It does represent a hardware resource.

Logical plane is not a hw concept, it just describes a group of one or
two HW planes. Then again, in the context of 2k+ displays, two HW planes
must always be used together, so that way it could be considered a
single HW resource.

>> Really, I'm skeptical that any of this belongs in DT. For example,
>> can't you figure out you need 2 physical planes whenever your
>> panel/timing width is greater than 2048?
> 
> As stated in the description I added above, we cannot have resources
> exposed to user-space which can "disappear" dynamically.
> Doing so would break user-space applications which rely on these
> resources.

The question is, if not in DT, then where? I agree that this is not
exactly describing the HW. But it can't be done dynamically either (or
at least we have not figured out a way). And it must be user configurable.

Module parameters are an option, but it would be somewhat difficult to
give all this information there. And also, if your board has a 2k+
display, you must have these configurations given to the driver, it's
not optional.

And while it's perhaps stretching the definitions a bit, I guess one
could argue that this describes the HW in a way: it describes how the HW
resources must be used if you have a display of 2k+ width, and is not as
such related to Linux or DRM.

 Tomi

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