[PATCH 4/4] drm/TODO: add a task to kill DRM_UNLOCKED

[Daniel Vetter]

On Wed, May 22, 2019 at 04:47:02PM +0100, Emil Velikov wrote:
> From: Emil Velikov <emil.velikov at collabora.com>
> 
> Should minimise the copy/paste mistakes, fixed with previous patches.
> 
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> ---
> Daniel, not 100% sold on the idea. That plus listing you as a contact
> point ;-)
> 
> What do you thing?
> Emil
> ---
>  Documentation/gpu/todo.rst | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index 66f05f4e469f..9e67d125f2fd 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -397,6 +397,25 @@ Some of these date from the very introduction of KMS in 2008 ...
>    end, for which we could add drm_*_cleanup_kfree(). And then there's the (for
>    historical reasons) misnamed drm_primary_helper_destroy() function.
>  
> +Use DRM_LOCKED instead of DRM_UNLOCKED
> +--------------------------------------
> +
> +DRM_UNLOCKED is a remainder from the legacy DRM drivers. Seemingly drivers get
> +tricked by it and it ends up in the driver private ioctls.
> +
> +Today no more legacy drivers are allowed and most core DRM ioctls are unlocked.
> +
> +Introduce DRM_LOCKED, use it to annotate only the relevant ioctls and kill the
> +old DRM_UNLOCKED.
> +
> +Patch series should be split as follows:
> + - Patch 1: drm: add the new DRM_LOCKED flag and honour it
> + - Patch 2: drm: convert core ioctls from DRM_UNLOCKED to DRM_LOCKED
> + - Patch 3-...: drm/driverX: convert driver ioctls from ...
> + - Patch X: drm: remove no longer used DRM_UNLOCKED, drop todo item

Seems like too much bother for legacy drivers ... What I'd do is something
a lot cheaper, since all we're touching here are legacy drivers:

Remove DRM_UNLOCKED from everything except the old vblank ioctl. That one
we need to keep, because it freezes X:

commit 8f4ff2b06afcd6f151868474a432c603057eaf56
Author: Ilija Hadzic <ihadzic at research.bell-labs.com>
Date:   Mon Oct 31 17:46:18 2011 -0400

    drm: do not sleep on vblank while holding a mutex

Anything else I think is either never used by legacy userspace, or just
doesn't matter. That's simple enough that I don't think we really need a
todo for it :-) I guess if you want to kill DRM_UNLOCKED you could replace
the check with ioctl->func == drm_vblank_ioctl, ofc only in the
DRIVER_LEGACY path.

On patches 1-3 in your series:

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Cheers, Daniel



> +
> +Contact: Emil Velikov, Daniel Vetter
> +
>  Better Testing
>  ==============
>  
> -- 
> 2.21.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch