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From: Philipp Zabel <p.zabel@pengutronix.de>
To: Ying Liu <gnuiyl@gmail.com>
Cc: kernel@pengutronix.de, DRI Development <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 10/10] drm/imx: ipuv3-plane: use drm_plane_helper_check_state, clipped coordinates
Date: Fri, 21 Oct 2016 10:18:22 +0200	[thread overview]
Message-ID: <1477037902.2508.5.camel@pengutronix.de> (raw)
In-Reply-To: <CAOcKUNWCgqMt666u6o3ueq+1+nnd0G0hViWh_4J-E2O9RtJLaw@mail.gmail.com>

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@pengutronix.de> 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

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  reply	other threads:[~2016-10-21  8:18 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-19 10:21 [PATCH 01/10] drm/imx: ipuv3-plane: make sure x/y offsets are even in case of chroma subsampling Philipp Zabel
2016-10-19 10:21 ` [PATCH 02/10] drm/imx: ipuv3-plane: disable local alpha for planes without alpha channel Philipp Zabel
2016-10-19 10:21 ` [PATCH 03/10] drm/imx: ipuv3-plane: request modeset if plane offsets changed Philipp Zabel
2016-10-19 10:21 ` [PATCH 04/10] drm/imx: ipuv3-plane: merge ipu_plane_atomic_set_base into atomic_update Philipp Zabel
2016-10-19 10:21 ` [PATCH 05/10] drm/imx: ipuv3-plane: let drm_plane_state_to_ubo/vbo handle chroma subsampling other than 4:2:0 Philipp Zabel
2016-10-20  6:19   ` Ying Liu
2016-10-19 10:21 ` [PATCH 06/10] gpu: ipu-cpmem: remove unused ipu_cpmem_set_yuv_planar function Philipp Zabel
2016-10-20  6:20   ` Ying Liu
2016-10-19 10:21 ` [PATCH 07/10] gpu: ipu-v3: add YUV 4:4:4 support Philipp Zabel
2016-10-19 10:21 ` [PATCH 08/10] drm/imx: ipuv3-plane: add support for YUV 4:2:2 and 4:4:4, NV12, and NV16 formats Philipp Zabel
2016-10-20  6:21   ` Ying Liu
2016-10-19 10:21 ` [PATCH 09/10] gpu: ipu-v3: initially clear all interrupts Philipp Zabel
2016-10-19 10:21 ` [PATCH 10/10] drm/imx: ipuv3-plane: use drm_plane_helper_check_state, clipped coordinates Philipp Zabel
2016-10-19 10:31   ` Ville Syrjälä
2016-10-19 10:46     ` Philipp Zabel
2016-10-20  7:53   ` Ying Liu
2016-10-20  8:41     ` Ville Syrjälä
2016-10-20  8:51       ` Ying Liu
2016-10-20 13:20         ` Ville Syrjälä
2016-10-20 13:29         ` Philipp Zabel
2016-10-21  5:45           ` Ying Liu
2016-10-21  8:18             ` Philipp Zabel [this message]
2016-10-21  8:49               ` Ying Liu
2016-10-24 11:50                 ` Philipp Zabel
2016-10-25  2:59                   ` Ying Liu
2016-10-20  6:18 ` [PATCH 01/10] drm/imx: ipuv3-plane: make sure x/y offsets are even in case of chroma subsampling Ying Liu

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