This adopts a "writer" concept, vaguely inspired by the ta parameter
writer. This might turn out to be not a great idea if the
response/offsets for heterogenous commands are too inconvenient to
keep track of.
This breaks every example that uses maple--only
example/maple_controller is updated to use the new interface.
Necessarily, this means that dma_start must now know what the size of the
response is, so that it can issue the appropriate number of ocbp instructions.
This also cleans up the inconsistent _command_buf and _recieve_buf declarations.
From the GCC manual.
> GCC permits a C structure to have no members:
struct empty {
};
> The structure has size zero. In C++, empty structures are part of the
> language. G++ treats empty structures as if they had a single member of type
> char.
I was not aware of the different behavior in C++.
This fixes every maple example--most were broken for multiple reasons, including
this one.
This also enables SH4 caching. This includes linking code/data into the P1
area (previously this was not the case).
The maple examples (which indeed involve much use of DMA) require much work to
successfully work with the operand and copyback caches. The vibration example
currently is the most complete, though I should consider more on how I want to
structure maple response operand cache invalidation more generally.
