On 07/12/2020 13:46, Sakari Ailus wrote: > Hi Hans, > > Thanks for the patch. > > On Mon, Dec 07, 2020 at 12:18:55PM +0100, Hans Verkuil wrote: >> This driver does not support composition, only cropping. >> Composition means that the sensor can output e.g. 1920x1080, >> but can compose a cropped 1280x720 image in the middle of the >> 1920x1080 canvas, filling in the unused area with a background >> color. > > That's how this would work on V4L2 video nodes... > >> >> That's not supported at all. So drop the bogus composition support. > > But this is a sub-device driver. On sub-devices the COMPOSE target is used > for configuring scaling, binning and sub-sampling. I don't know about the > capabilities of this particular driver but the code > (__imx274_change_compose function in particular) looks very much such that > it does support binning. > That should be done via set_fmt. There you select the output width and height. So if set_fmt sets 1920x1080, and the crop is 960x540, then you scale (or do binning/sub-sampling). Compose means composing the image into a larger canvas. For this driver the compose rectangle is always equal to the format, so set_selection(COMPOSE) is identical to set_fmt(). If it was real composition, then there would have to be a try_compose as well, just as there is a try_crop. Instead set_selection(COMPOSE) fills in try_fmt. Clearly wrong. Regards, Hans
