Re: [PATCH v2] Documentation: media: *_DEFAULT targets for subdevs

[Sakari Ailus]

Hi Ricardo,

On Thu, Oct 24, 2019 at 03:43:36PM +0200, Ricardo Ribalda Delgado wrote:
> Hi Sakari
> 
> Lets say the user wants to select the active pixels. He needs to set
> the crop and the compose.
> 
> 1) he gets V4L2_SEL_TGT_CROP_DEFAULT
> 
> 2) he sets V4L2_SEL_TGT_CROP
> 
> How does he knows which compose to use? What if the compose starts at
> (0,0) instead of (32,32)....?
> 
> I think it is easier if
> 
> 3) he gets V4L2_SEL_TGT_COMPOSE_DEFAULT
> 
> 4) he sets V4L2_SEL_TGT_COMPOSE
> 
> This is similar as how we do it today with a v4l2_device. What if we
> simply replicate that behaviour?

The compose rectangle is relative to the crop rectangle (if there's a crop
rectangle), and always starts at 0,0.

See:

<URL:https://hverkuil.home.xs4all.nl/spec/uapi/v4l/dev-subdev.html#selections-cropping-scaling-and-composition>

-- 
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxx