Le 08/05/2020 à 03:51, Jordan Niethe a écrit :

On Wed, May 6, 2020 at 1:45 PM Jordan Niethe [off-list ref] wrote:

quoted

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 endianness 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.

Signed-off-by: Jordan Niethe <redacted>
---
v4: New to series
v5: Add to epapr_paravirt.c, kgdb.c
v6: - setup_32.c: machine_init(): Use type
     - feature-fixups.c: do_final_fixups(): Use type
     - optprobes.c: arch_prepare_optimized_kprobe(): change a void * to
       struct ppc_inst *
     - fault.c: store_updates_sp(): Use type
     - Change ppc_inst_equal() implementation from memcpy()
v7: - Fix compilation issue in early_init_dt_scan_epapr() and
       do_patch_instruction() with CONFIG_STRICT_KERNEL_RWX
v8: - style
     - Use in crash_dump.c, mpc86xx_smp.c, smp.c
---

[...]

Why not declare stard and end as struct ppc_inst ? Wouldn't it be 
cleaner than a cast ?

Christophe