On 25-08-2025 15:17, Jani Nikula wrote:
On Sat, 23 Aug 2025, "Murthy, Arun R" <arun.r.mur...@intel.com> wrote:
On 22-08-2025 21:44, Xaver Hugl wrote:
+#define DRM_MODE_ATOMIC_FAILURE_REASON \
+ FAILURE_REASON(DRM_MODE_ATOMIC_CAP_NOT_ENABLED, "DRM_ATOMIC capability not
enabled") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_INVALID_FLAG, "invalid flag") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_PAGE_FLIP_ASYNC, "Legacy
DRM_MODE_PAGE_FLIP_ASYNC not to be used in atomic ioctl") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_FLIP_EVENT_WITH_CHECKONLY, "requesting
page-flip event with TEST_ONLY") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_CRTC_NEED_FULL_MODESET, "Need full modeset on
this crtc") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_NEED_FULL_MODESET, "Need full modeset on all
the connected crtc's") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_ASYNC_NOT_SUP_PLANE, "Async flip not
supported on this plane") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_ASYNC_MODIFIER_NOT_SUPPORTED, "Modifier not
supported on this plane with async flip") \
+ FAILURE_REASON(DRM_MODE_ATOMIC_ASYNC_PROP_CHANGED, "No property change
allowed when async flip is enabled")
As mentioned before, some of these errors are a bit too specific. We
don't need to have an enum value for every way the API can be used
wrongly - CAP_NOT_ENABLED, INVALID_FLAG, PAGE_FLIP_ASYNC and
MODIFIER_NOT_SUPPORTED should all just be one enum value for "invalid
API usage".
In general, there should only be enum values that the compositor
implementation can actually use on end-user systems. For further
information when debugging a broken compositor implementation, other
tools can be used instead, like drm debug logging or the returned
string.
I have considered your comment in the last series and have removed
driver specific errors.
Anyway will have a look again on this and will get back.
+#define FAILURE_REASON(flag, reason) flag,
+typedef enum {
+ DRM_MODE_ATOMIC_FAILURE_REASON
+} drm_mode_atomic_failure_flag;
+#undef FAILURE_REASON
+
+#define FAILURE_REASON(flag, reason) #reason,
+extern const char *drm_mode_atomic_failure_string[];
+#undef FAILURE_REASON
The intention for the string wasn't for the enum values to be paired
with a description of the enum - that belongs into documentation, not
uAPI.
The idea behind it was that drivers could add driver-specific
information in the string for compositors to log (only in commits
where failure isn't normally expected), so we have an easier time
debugging issues a user system experienced by looking at the
compositor logs. Sending the enum value again in string form isn't
useful.
We are not sending enum value in string. Its just a single place where
we have both enum and string. Upon user adding new error codes if both
enum and string are at a single place it would be easy for the user.
Hence adding both in a single place using X macros.
Its not mandatory to have a string for every enum, the string can be
left empty if not required, or later in the driver user can overwrite
the string as well.
See my reply [1] about fixed vs. non-fixed error messages.
I believe Xaver is also saying we don't want the fixed error messages,
and especially not in a uapi header.
BR,
Jani.
[1] https://lore.kernel.org/r/419591dda7158b3d56c40aac0df86ca499202...@intel.com
As pointed out in option C of [2] I also feel better to have a default
message so that
compositor can use it for logging.
Thanks and Regards,
Arun R Murthy
--------------------
[2]
https://lore.kernel.org/all/419591dda7158b3d56c40aac0df86ca499202...@intel.com/
