Am Freitag, den 21.10.2016, 13:45 +0800 schrieb Ying Liu: > On Thu, Oct 20, 2016 at 9:29 PM, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote: > > Am Donnerstag, den 20.10.2016, 16:51 +0800 schrieb Ying Liu: > >> >> Does the clip thing potentially change the user's request by force? > >> >> For example, the user request an unreasonable big resolution. > >> > > >> > The user is allowed to ask for destination coordinates extending outside > >> > the crtc dimensions. This will chop off the parts that aren't visible, > >> > and it will chop off the corresponding areas of the source as well. > >> > >> How about returning -EINVAL in this case which stands for > >> an atomic check failure? > > > > Say the user requests to display a 640x480+0,0 source framebuffer at > > destination offset -320,0 on a 320x240 screen, unscaled. The expectation > > would be to see the upper right quarter of the framebuffer on the > > screen, at least if the hardware was actually able to position overlays > > partially offscreen. > > If we can also fulfill that expectation by clipping the source rectangle > > to 320,240+320,0 and changing the destination rectangle to 320x240+0,0, > > why should -EINVAL be returned? > > Well, IIUC, there are two kinds of clipping. > 1) Clipping a rectangle from a fb according to src_x/y and src_w/h. > 2) Clipping done by drm_plane_helper_check_state(), which potentially > changes src/dst->x1/2 and src/dst->y1/2(in other words, src_x/y, > src_w/h and crtc_x/y/w/h, though not directly). > > 1) is fine, no problem. > I doubt 2) is wrong as the users' original request could be changed. > That's why I mentioned returning -EINVAL. > > Moreover, before and after applying the patch, I think the > ->atomic_check behavior consistency is broken. For example, > negative crtc_x or crtc_y for overlay are changed from unacceptable > to potentially acceptable just because 2) may change their equivalent > dst_>x/y1. I fail to see what's wrong with 2) as long as we can keep the observable behaviour exactly the same as if the user request was unchanged. regards Philipp _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
