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    SubjectRe: [PATCH 1/3] drm: add gem ttm helpers
    > > +/**
    > > + * drm_gem_ttm_mmap_offset() - Returns a GEM ttm object's mmap offset
    > > + * @gbo: the GEM ttm object
    > > + *
    > > + * See drm_vma_node_offset_addr() for more information.
    > > + *
    > > + * Returns:
    > > + * The buffer object's offset for userspace mappings on success, or
    > > + * 0 if no offset is allocated.
    > > + */
    > > +u64 drm_gem_ttm_mmap_offset(struct ttm_buffer_object *bo)
    > > +{
    > > + return drm_vma_node_offset_addr(&bo->base.vma_node);
    >
    > Why do we need a new one here, can't we use the existing gem
    > implementation for this (there really should only be one I hope, but I
    > didn't check).

    Havn't found one.

    But maybe we don't need this as separate function and can simply move
    the drm_vma_node_offset_addr() call into
    drm_gem_ttm_driver_dumb_mmap_offset().

    > > +int drm_gem_ttm_driver_dumb_mmap_offset(struct drm_file *file,
    > > + struct drm_device *dev,
    > > + uint32_t handle, uint64_t *offset)
    > > +{
    > > + struct drm_gem_object *gem;
    > > + struct ttm_buffer_object *bo;
    > > +
    > > + gem = drm_gem_object_lookup(file, handle);
    > > + if (!gem)
    > > + return -ENOENT;
    > > +
    > > + bo = drm_gem_ttm_of_gem(gem);
    > > + *offset = drm_gem_ttm_mmap_offset(bo);
    > > +
    > > + drm_gem_object_put_unlocked(gem);
    > > +
    > > + return 0;
    > > +}
    > > +EXPORT_SYMBOL(drm_gem_ttm_driver_dumb_mmap_offset);
    >
    > Same for this, you're just upcasting to ttm_bo and then downcasting to
    > gem_bo again ... I think just a series to roll out the existing gem
    > helpers everywhere should work?

    I don't think so. drm_gem_dumb_map_offset() calls
    drm_gem_create_mmap_offset(), which I think is not correct for ttm
    objects because ttm_bo_init() handles vma_node initialization.

    cheers,
    Gerd

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