On 08/04/2016 04:17 PM, Sakari Ailus wrote: > On Thu, Aug 04, 2016 at 04:11:55PM +0200, Hans Verkuil wrote: >> >> >> On 08/04/2016 04:03 PM, Sakari Ailus wrote: >>> Hi Hans, >>> >>> On Mon, Aug 01, 2016 at 12:33:39PM +0200, Hans Verkuil wrote: >>>> Checking the selection constraint flags is often forgotten by drivers, especially >>>> if the selection code just clamps the rectangle to the minimum and maximum allowed >>>> rectangles. >>>> >>>> This patch adds a simple helper function that checks the adjusted rectangle against >>>> the constraint flags and either returns -ERANGE if it doesn't fit, or fills in the >>>> new rectangle and returns 0. >>>> >>>> It also adds a small helper function to v4l2-rect.h to check if one rectangle fits >>>> inside another. >>> >>> I could have misunderstood the purpose of the patch but... these flags are >>> used by drivers in guidance in adjusting the rectangle in case there are >>> hardware limitations, to make it larger or smaller than requested if the >>> request can't be fulfillsed as such. The intent is *not* to return an error >>> back to the user. In this respect it works quite like e.g. S_FMT does in >>> cases an exact requested format can't be supported. >>> >>> <URL:https://www.linuxtv.org/downloads/v4l-dvb-apis/apb.html#v4l2-selection-flags> >>> >>> What can be done is rather driver specific. >>> >> >> That's not what the spec says: >> >> https://hverkuil.home.xs4all.nl/spec/uapi/v4l/vidioc-g-selection.html >> >> ERANGE >> It is not possible to adjust struct v4l2_rect r rectangle to satisfy all constraints given in the flags argument. >> >> It's rather unambiguous, I think. >> >> If you don't want an error, then just leave 'flags' to 0. That makes sense. > > Does it? I can't imagine a use case for that. That's just the standard behavior: "I'd like this selection rectangle, but adjust however you like it to something that works." > The common section still defines these flags differently, and that's the > behaviour on V4L2 sub-device interface. Do we have a driver that implements > support for these flags as you described? > A quick check: fimc-capture, gsc-m2m, am437, vivid, fimc-lite, bdisp. Note that VIDIOC_SUBDEV_S_SELECTION doesn't specify an ERANGE error, but I don't know if that is intentional or an oversight. At least smiapp-core.c doesn't return an error. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
