Jordan Niethe's on March 23, 2020 7:28 pm: > On Mon, Mar 23, 2020 at 5:27 PM Nicholas Piggin <npig...@gmail.com> wrote: >> >> Jordan Niethe's on March 20, 2020 3:17 pm: >> > Currently unsigned ints are used to represent instructions on powerpc. >> > This has worked well as instructions have always been 4 byte words. >> > However, a future ISA version will introduce some changes to >> > instructions that mean this scheme will no longer work as well. This >> > change is Prefixed Instructions. A prefixed instruction is made up of a >> > word prefix followed by a word suffix to make an 8 byte double word >> > instruction. No matter the endianess of the system the prefix always >> > comes first. Prefixed instructions are only planned for powerpc64. >> > >> > Introduce a ppc_inst type to represent both prefixed and word >> > instructions on powerpc64 while keeping it possible to exclusively have >> > word instructions on powerpc32, A latter patch will expand the type to >> > include prefixed instructions but for now just typedef it to a u32. >> > >> > Later patches will introduce helper functions and macros for >> > manipulating the instructions so that powerpc64 and powerpc32 might >> > maintain separate type definitions. >> >> ppc_inst_t I would slightly prefer for a typedef like this. > Are _t types meant to be reserved?
No, just convention that structs are not normally typedefed unless they are a pervasive interface that gets passed around a lot but does not get accessed without accessor functions much. When you do typedef them, add a _t (or less frequently _s/_u/etc). pte_t, cpumask_t, atomic_t. Thanks, Nick
