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Subject: Re: [PATCH v2 7/8] drm/virtio: Support memory shrinking
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To:     Emil Velikov <emil.l.velikov@gmail.com>
Cc:     David Airlie <airlied@linux.ie>, Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
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        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Herring <robh@kernel.org>,
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        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        ML dri-devel <dri-devel@lists.freedesktop.org>,
        Dmitry Osipenko <digetx@gmail.com>
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From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
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On 3/15/22 15:43, Emil Velikov wrote:
> Greetings everyone,
> 
> Food for thought: Would it make sense to have the madvise ioctl as
> generic DRM one?
> Looking around - i915, msm & panfrost already have one and the virtio
> implementation [below] seems as generic as it gets.
> 
> On Mon, 14 Mar 2022 at 22:44, Dmitry Osipenko
> <dmitry.osipenko@collabora.com> wrote:
> 
>> +#define VIRTGPU_MADV_WILLNEED 0
>> +#define VIRTGPU_MADV_DONTNEED 1
>> +struct drm_virtgpu_madvise {
>> +       __u32 bo_handle;
>> +       __u32 retained; /* out, non-zero if BO can be used */
>> +       __u32 madv;
>> +       __u32 pad;
> 
> This seems to be based on panfrost/msm yet names (bo_handle vs
> handle), layout and documentation varies.
> Why is that - copy/paste is cheap :-P

Indeed, there is copy/pasting among drivers. But I'm doubtful about
making madvise a generic ioctl because some drivers already have own
ioctl for that and h/w capabilities vary, so some drivers may want to
have extra features later on and then this doesn't feel like a common
thing anymore.