I sent through a patch a while ago that fixed building YAFFS on new kernels (https://yaffs.net/lurker/message/20170507.214229.ce03d9f1.pt-BR.html). But the way it did that was basically by disabling xattr support. I've got a new patch which reinstates it again, but it's a bit more invasive since we now end up with three different prototypes for the yaffs_getxattr & yaffs_setxattr functions.