Yes I think we are on the same page. I think my original proposal would work up to the layout transform stage, but I now realized the possibility of type inference failure (since the function takes NCHWc layout but the convolution inside is still nn.conv2d from Relay perspective), if extern function is not treated as a opaque op (like @anijain2305 mentioned) during type inference.
@anijain2305 AlterOpLayout is associated with each target (x86, ARM). If I decide to run a layout transform pass before BYOC, I want to convert NCHW convolutions to NCHWc convolution according to my need (the choice of inner c dim etc). Is ConvertLayout the right pass to use here? I have no experience with this.