Only a little. The bulk of the complexity for large data like textures isn't around the dma transfer, it's instead around things like ensuring data is properly aligned, that things like textures are swizzled if that format is even documented at all, and ensuring it's actually safe to read or write to the buffer (that is, that the GPU isn't still using it). Also in actually allocating memory in that a malloc/free isn't really provided, rather something like mmap is instead. So you want a (re)allocator on top of that.
And there's also the complexity of things like Vulkan want to work on both unified and non-unified systems.
Also unified doesn't necessarily mean coherent, so there's additional complexities there.
