On Sat, 5 Jun 2021, Michael Schmitz wrote:
Am 04.06.2021 um 19:54 schrieb Geert Uytterhoeven:
I have to wonder whether there is a nice simple definition for
MULTI_ISA.
As I understand it, MULTI_ISA means that different byte orders
and/or different address translations need to be used in the same
kernel, so all that cannot be decided at build time.
As long as there is only a single platform that will use this code
(ISA only used on a single platform, and neither Atari IDE nor
EtherNEC used), MULTI_ISA is not needed.
If we have Kconfig symbols for 'single platform only', and
'multi-platform ISA use', that might be shorter to write and easier
to understand. Geert?
It would be nice to have that automatically, like with the current
MULTI_ISA define (and all the MACH_* in
arch/m68k/include/asm/setup.h). Perhaps we should extend kconfig
syntax to define a group of related symbols, and to automatically
generate CONFIG_FOO_MULTI or CONFIG_FOO_SINGLE (and even
CONFIG_BAR_ONLY?) symbols?
I take it this is not supported by our current Kconfig syntax?
That may be because CPP hacking is seen as a competitive sport in some
circles.
group ISA
item ATARI_ROM_ISA
item AMIGA_PCMCIA
item Q40
=> CONFIG_ISA_MULTI or CONFIG_ISA_SINGLE (+ e.g. ATARI_ROM_ISA_ONLY
if appropriate).
Since the items may be bools or tristates, it not clear what type the
group has.
Anyway, I see that we can already write this:
#define IS_MULTI(a,b) __or(IS_ENABLED(a), IS_ENABLED(b))
So maybe we just need an exclusive-OR macro to go with the other operators
defined in include/linux/kconfig.h? Then we could write this:
#define IS_SINGLE(a,b) __xor(IS_ENABLED(a), IS_ENABLED(b))
But these only work for a 2-way group. Extending them to N-way groups is
beyond my CPP abilities. It probably requires N-way __or() and __xor()...
