It's not obvious what the fields mean and how they should be used. The most important detail is the link to drm_property.flags, which describes how property types work.
v2: document enum drm_mode_property_enum, add ref to "Modeset Base Object Abstraction" (Daniel)
Signed-off-by: Simon Ser contact@emersion.fr Acked-by: Pekka Paalanen pekka.paalanen@collabora.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Leandro Ribeiro leandro.ribeiro@collabora.com ---
I couldn't figure out how to linkify that ref, so it's not linkified.
Documentation/gpu/drm-kms.rst | 2 ++ include/uapi/drm/drm_mode.h | 60 ++++++++++++++++++++++++++++++++--- 2 files changed, 58 insertions(+), 4 deletions(-)
diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst index 0cc21f6aaef5..1ef7951ded5e 100644 --- a/Documentation/gpu/drm-kms.rst +++ b/Documentation/gpu/drm-kms.rst @@ -159,6 +159,8 @@ KMS Core Structures and Functions .. kernel-doc:: drivers/gpu/drm/drm_mode_config.c :export:
+.. _kms_base_object_abstraction: + Modeset Base Object Abstraction ===============================
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h index 98bf130feda5..90c55383f1ee 100644 --- a/include/uapi/drm/drm_mode.h +++ b/include/uapi/drm/drm_mode.h @@ -541,22 +541,74 @@ struct drm_mode_get_connector { */ #define DRM_MODE_PROP_ATOMIC 0x80000000
+/** + * struct drm_mode_property_enum - Description for an enum/bitfield entry. + * @value: numeric value for this enum entry. + * @name: symbolic name for this enum entry. + * + * See struct drm_property_enum for details. + */ struct drm_mode_property_enum { __u64 value; char name[DRM_PROP_NAME_LEN]; };
+/** + * struct drm_mode_get_property - Get property metadata. + * + * User-space can perform a GETPROPERTY ioctl to retrieve information about a + * property. The same property may be attached to multiple objects, see + * "Modeset Base Object Abstraction". + * + * The meaning of the @values_ptr field changes depending on the property type. + * See &drm_property.flags for more details. + * + * The @enum_blob_ptr and @count_enum_blobs fields are only meaningful when the + * property has the type &DRM_MODE_PROP_ENUM or &DRM_MODE_PROP_BITMASK. For + * backwards compatibility, the kernel will always set @count_enum_blobs to + * zero when the property has the type &DRM_MODE_PROP_BLOB. User-space must + * ignore these two fields if the property has a different type. + * + * User-space is expected to retrieve values and enums by performing this ioctl + * at least twice: the first time to retrieve the number of elements, the + * second time to retrieve the elements themselves. + * + * To retrieve the number of elements, set @count_values and @count_enum_blobs + * to zero, then call the ioctl. @count_values will be updated with the number + * of elements. If the property has the type &DRM_MODE_PROP_ENUM or + * &DRM_MODE_PROP_BITMASK, @count_enum_blobs will be updated as well. + * + * To retrieve the elements themselves, allocate an array for @values_ptr and + * set @count_values to its capacity. If the property has the type + * &DRM_MODE_PROP_ENUM or &DRM_MODE_PROP_BITMASK, allocate an array for + * @enum_blob_ptr and set @count_enum_blobs to its capacity. Calling the ioctl + * again will fill the arrays. + */ struct drm_mode_get_property { - __u64 values_ptr; /* values and blob lengths */ - __u64 enum_blob_ptr; /* enum and blob id ptrs */ + /** @values_ptr: Pointer to a ``__u64`` array. */ + __u64 values_ptr; + /** @enum_blob_ptr: Pointer to a struct drm_mode_property_enum array. */ + __u64 enum_blob_ptr;
+ /** + * @prop_id: Object ID of the property which should be retrieved. Set + * by the caller. + */ __u32 prop_id; + /** + * @flags: ``DRM_MODE_PROP_*`` bitfield. See &drm_property.flags for + * a definition of the flags. + */ __u32 flags; + /** + * @name: Symbolic property name. User-space should use this field to + * recognize properties. + */ char name[DRM_PROP_NAME_LEN];
+ /** @count_values: Number of elements in @values_ptr. */ __u32 count_values; - /* This is only used to count enum values, not blobs. The _blobs is - * simply because of a historical reason, i.e. backwards compat. */ + /** @count_enum_blobs: Number of elements in @enum_blob_ptr. */ __u32 count_enum_blobs; };