On Mon, 31 Dec 2018, Arnd Bergmann wrote: > On Sun, Dec 30, 2018 at 4:29 AM Finn Thain <fth...@telegraphics.com.au> 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 >
