Re: [PATCH RFC 0/8] drm: Add DRM_MODE_ATOMIC_RESET flag

["Michel Dänzer" <michel.daenzer@mailbox.org>]

On 7/8/26 18:08, Maxime Ripard wrote:
> 
> Userspace currently has no atomic way to bring a display pipeline back
> to a pristine state. A compositor that wants to start from a known
> baseline must explicitly set every property on every KMS object to its
> default value, which requires tracking which properties exist and what
> their defaults are. This is fragile and must be updated every time a
> new property is added to the kernel.
> 
> This series introduces a new DRM_MODE_ATOMIC_RESET flag for the
> atomic ioctl. When set, the kernel fills the commit with default
> states for all KMS objects before applying the properties supplied in
> the request. Properties not explicitly included remain at their
> defaults (CRTCs inactive, planes disabled, connectors unbound, and so
> on). This allows userspace to describe the desired end state
> declaratively, without having to care about the current state or the
> full set of properties.

Nice!


> Patch 8 wires it all up by adding DRM_MODE_ATOMIC_RESET to the atomic
> ioctl.

The new flag should be accompanied by a new DRM_CAP_* cap, so user space knows when the new flag is valid.


> This series is untested and relies on all drivers implementing the
> atomic_create_state hook, which is not yet the case. The conversion
> is actively in progress but not complete, so this will not work as-is
> today.

As discussed on IRC, the new cap could be made conditional on the atomic_create_state hook being available. That would allow this series to land before all in-tree drivers are converted. (As a bonus, it would also avoid issues with out-of-tree drivers which might not support the atomic_create_state hook)


-- 
Earthling Michel Dänzer       \        GNOME / Xwayland / Mesa developer
https://redhat.com             \               Libre software enthusiast