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From:   Rob Clark <robdclark@gmail.com>
Date:   Thu, 9 Sep 2021 09:35:31 -0700
Message-ID: <CAF6AEGuD2bnFpmSWtGxU5+AFj1HVKtnOZmLKRr-pDVbLn0nPVw@mail.gmail.com>
Subject: Re: [PATCH v3 0/9] dma-fence: Deadline awareness
To:     Simon Ser <contact@emersion.fr>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@lists.linaro.org>, Daniel Vetter <daniel@ffwll.ch>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>,
        =?UTF-8?Q?Michel_D=C3=A4nzer?= <michel@daenzer.net>,
        Pekka Paalanen <ppaalanen@gmail.com>,
        Rob Clark <robdclark@chromium.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Andrey Grodzovsky <andrey.grodzovsky@amd.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        freedreno <freedreno@lists.freedesktop.org>,
        Gustavo Padovan <gustavo@padovan.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@vger.kernel.org>, Luben Tuikov <luben.tuikov@amd.com>,
        Melissa Wen <mwen@igalia.com>,
        Steven Price <steven.price@arm.com>,
        Tian Tao <tiantao6@hisilicon.com>
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On Thu, Sep 9, 2021 at 9:16 AM Simon Ser <contact@emersion.fr> wrote:
>
> Out of curiosity, would it be reasonable to allow user-space (more
> precisely, the compositor) to set the deadline via an IOCTL without
> actually performing an atomic commit with the FB?
>
> Some compositors might want to wait themselves for FB fence completions
> to ensure a client doesn't block the whole desktop (by submitting a
> very costly rendering job). In this case it would make sense for the
> compositor to indicate that it intends to display the buffer on next
> vblank if it's ready by that point, without queueing a page-flip yet.

Yes, I think it would.. and "dma-buf/sync_file: Add SET_DEADLINE
ioctl" adds such an ioctl.. just for the benefit of igt tests at this
point, but the thought was it would be also used by compositors that
are doing such frame scheduling.  Ofc danvet is a bit grumpy that
there isn't a more real (than igt) userspace for the ioctl yet ;-)

BR,
-R