On Mon, 31 Dec 2018, Arnd Bergmann wrote:
On Sun, Dec 30, 2018 at 4:29 AM Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> wrote:
On Sat, 29 Dec 2018, Arnd Bergmann wrote:
With the current method, it does seem odd to have a single
per-architecture instance of the exported structure containing
function pointers. This doesn't give us the flexibility of having
multiple copies in the kernel the way that ppc_md does, but it adds
overhead compared to simply exporting the functions directly.
You're right, there is overhead here.
With a bit of auditing, wrappers like the one you quoted (which merely
checks whether or not a ppc_md method is implemented) could surely be
avoided.
The arch_nvram_ops methods are supposed to optional (that is, they are
allowed to be NULL).
We could call exactly the same function pointers though either ppc_md
or arch_nvram_ops. That would avoid the double indirection.
I think you can have a 'const' structure in the __ro_after_init section,
so without changing anything else, powerpc could just copy the function
pointers from ppc_md into the arch_nvram_ops at early init time, which
should ideally simplify your implementation as well.
Does this require removing the 'const' from the powerpc arch_nvram_ops
definition? That would mean removing the 'const' from the declaration in
nvram.h, which means removing 'const' for every other instance of that
struct too.
That's what happened when I tried removing the ppc_md.nvram_* methods
entirely and assigning the same function pointers to arch_nvram_ops
methods instead. Apparently all instances of arch_nvram_ops have to be
const or none of them. Otherwise gcc says, "error: conflicting type
qualifiers for 'arch_nvram_ops'".
--
Arnd
