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. 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
