https://bugs.freedesktop.org/show_bug.cgi?id=97305
--- Comment #9 from Ilia Mirkin imirkin@alum.mit.edu --- (In reply to Marek Olšák from comment #5)
Pre-GCN cards require an alignment of 256 bytes for uniform buffers. GCN cards only require 4 byte alignment there.
All other buffer binding points require 1, 2, or 4 bytes depending on the texel size. It's really min(texel_size, 4).
That means that you have to return max(texel_size) for the GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT. You only get one cap, and a texture buffer can be any offset.