Re: [Intel-gfx] [PATCH 1/3] drm/atomic: Take the atomic toys away from X

[Rob Clark <robdclark@gmail.com>]

On Tue, Sep 3, 2019 at 12:07 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> The -modesetting ddx has a totally broken idea of how atomic works:
> - doesn't disable old connectors, assuming they get auto-disable like
>   with the legacy setcrtc
> - assumes ASYNC_FLIP is wired through for the atomic ioctl
> - not a single call to TEST_ONLY
>
> Iow the implementation is a 1:1 translation of legacy ioctls to
> atomic, which is a) broken b) pointless.
>
> We already have bugs in both i915 and amdgpu-DC where this prevents us
> from enabling neat features.
>
> If anyone ever cares about atomic in X we can easily add a new atomic
> level (req->value == 2) for X to get back the shiny toys.
>
> Since these broken versions of -modesetting have been shipping,
> there's really no other way to get out of this bind.
>
> References: https://gitlab.freedesktop.org/xorg/xserver/issues/629
> References: https://gitlab.freedesktop.org/xorg/xserver/merge_requests/180
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Michel Dänzer <michel@daenzer.net>
> Cc: Alex Deucher <alexdeucher@gmail.com>
> Cc: Adam Jackson <ajax@redhat.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: David Airlie <airlied@linux.ie>
> Cc: stable@vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/drm_ioctl.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 2c120c58f72d..1cb7b4c3c87c 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -334,6 +334,9 @@ drm_setclientcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
>                 file_priv->universal_planes = req->value;
>                 break;
>         case DRM_CLIENT_CAP_ATOMIC:
> +               /* The modesetting DDX has a totally broken idea of atomic. */
> +               if (strstr(current->comm, "X"))
> +                       return -EOPNOTSUPP;

Seems like we can be a bit more targeted than "anything that has 'X'
in the name".. at a minimum restrict things to "starts with 'X'" seems
saner.  But I guess we could probably somehow look at the processes
memory map and look for modesetting_drv.so.

BR,
-R

>                 if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
>                         return -EOPNOTSUPP;
>                 if (req->value > 1)
> --
> 2.23.0
>
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