Re: [PATCH v10 0/7] User readable error codes on atomic_ioctl failure

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Feb 24, 2026 at 12:46:10PM +0530, Murthy, Arun R wrote:
> On 24-02-2026 12:37, Ville Syrjälä wrote:
> > On Mon, Feb 23, 2026 at 03:37:39PM +0530, Murthy, Arun R wrote:
> >> Any other comments/feedback on this?
> > Having random strings as uabi seems like a bad idea.
> > How would you make sure those are never changed?
> The requirement was to have a string for logging/debugging in the UMD 
> logs and KMD/display to pass the verbose information.
> 
> Discussions around this.[1][2]
> 
> [1] https://hackmd.io/f3bDn3kyRUalLn4LbMfCVQ#Commit-Failure-Feedback
> 
> [2] https://patchwork.freedesktop.org/patch/666193/?series=152276&rev=1

So the enum+obj_id thing there is perhaps the only thing that makes
sense for compositors.

Although I kinda doubt its actual usefulness to drive useful
fallback logic because often the restrictions might be a combination
of many things, and the kernel can only realistically report one of
those things.

Anyways, someone really needs to do the actual compositor
implementation so that we could see how any of this would
even work in practice.

> Thanks and Regards,
> Arun R Murthy
> -------------------
> 
> >> Thanks and Regards,
> >> Arun R Murthy
> >> -------------------
> >>
> >> On 23-02-2026 14:45, Arun R Murthy wrote:
> >>> EDITME: Imported from f20260210-atomic-v9-5-525c88fd2402@intel.com
> >>>           Please review before sending.
> >>>
> >>> The series focuses on providing a user readable error value on a failure
> >>> in drm_atomic_ioctl(). Usually -EINVAL is returned in most of the error
> >>> cases and it is difficult for the user to decode the error and get to
> >>> know the real cause for the error. If user gets to know the reason for
> >>> the error then corrective measurements can be taken up.
> >>>
> >>> User will have to check for the capability
> >>> DRM_CAP_ATOMIC_ERROR_REPORTING before using this feature so as to ensure
> >>> that the driver supports failure reporting.
> >>>
> >>> TODO: driver specific error codes are to be added and will be done in
> >>> the follow-up patches.
> >>>
> >>> TODO: Once the series is merged the element 'reserved' used for sending
> >>> the failure code in struct drm_mode_atomic is to changed to err_code.
> >>>
> >>> The IGT related changes are pushed for review @
> >>> https://patchwork.freedesktop.org/series/153330/
> >>>
> >>> [RFC] changes for libdrm pushed for review @
> >>> https://gitlab.freedesktop.org/mesa/libdrm/-/merge_requests/450
> >>>
> >>>       To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>       To: suraj.kandpal@intel.com>
> >>>       To: Maxime Ripard <mripard@kernel.org>
> >>>       To: Thomas Zimmermann <tzimmermann@suse.de>
> >>>       To: David Airlie <airlied@gmail.com>
> >>>       To: Simona Vetter <simona@ffwll.ch>
> >>>       To: Jani Nikula <jani.nikula@linux.intel.com>
> >>>       To: Rodrigo Vivi <rodrigo.vivi@intel.com>
> >>>       To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> >>>       To: Tvrtko Ursulin <tursulin@ursulin.net>
> >>>       To: xaver.hugl@kde.org
> >>>       To: harry.wentland@amd.com
> >>>       To: uma.shankar@intel.com
> >>>       To: louis.chauvet@bootlin.com
> >>>       To: naveen1.kumar@intel.com
> >>>       To: ramya.krishna.yella@intel.com
> >>>       Cc: dri-devel@lists.freedesktop.org 
> >>>       Cc: intel-gfx@lists.freedesktop.org
> >>>       Cc: intel-xe@lists.freedesktop.org
> >>>       Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
> >>>
> >>> Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
> >>> ---
> >>> Changes in v9:
> >>> - EDITME: describe what is new in this series revision.
> >>> - EDITME: use bulletpoints and terse descriptions.
> >>> - Link to v8: https://lore.kernel.org/r/20260129-atomic-v8-0-4cb7b0faa051@intel.com
> >>>
> >>> ---
> >>> Arun R Murthy (7):
> >>>         drm: Define user readable error codes for atomic ioctl
> >>>         drm/atomic: Add error_code element in atomic_state
> >>>         drm/atomic: Call complete_signaling only if prepare_signaling is done
> >>>         drm/atomic: Allocate atomic_state at the beginning of atomic_ioctl
> >>>         drm/atomic: Return user readable error in atomic_ioctl
> >>>         drm/i915/display: Error codes for async flip failures
> >>>         drm: Introduce DRM_CAP_ATOMIC_ERROR_REPORTING
> >>>
> >>>    drivers/gpu/drm/drm_atomic.c                 | 31 ++++++++++
> >>>    drivers/gpu/drm/drm_atomic_uapi.c            | 89 ++++++++++++++++++++--------
> >>>    drivers/gpu/drm/drm_ioctl.c                  |  3 +
> >>>    drivers/gpu/drm/i915/display/intel_display.c | 25 ++++----
> >>>    include/drm/drm_atomic.h                     | 10 ++++
> >>>    include/uapi/drm/drm.h                       |  7 +++
> >>>    include/uapi/drm/drm_mode.h                  | 37 ++++++++++++
> >>>    7 files changed, 165 insertions(+), 37 deletions(-)
> >>> ---
> >>> base-commit: cec43d5c2696af219fc2ef71dd7e93db48c80f66
> >>> change-id: 20250728-atomic-c9713fd357e4
> >>>
> >>> Best regards,

-- 
Ville Syrjälä
Intel