Re: [PATCH v11 0/7] User readable error codes on atomic_ioctl failure

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 31.03.26 um 11:03 schrieb Arun R Murthy:
> 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.

I'm missing some comments on related work. Other subsystems (filesystems 
IIRC) have explored various ideas for extending errno codes. But nothing 
was deemed acceptable. I'd like to know why this works with DRM, but not 
other subsystems.

Best regards
Thomas

>
> 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
>
> [DRAFT] KWin changes are pushed for review @
> https://invent.kde.org/plasma/kwin/-/merge_requests/8991
>
>      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                  | 56 +++++++++++++++++
>   7 files changed, 184 insertions(+), 37 deletions(-)
> ---
> base-commit: 65b94118bc585aefc7095c0e9554c3bb12d98a69
> change-id: 20250728-atomic-c9713fd357e4
>
> Best regards,

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri, (HRB 36809, AG Nürnberg)