On Wed, Feb 21, 2018 at 1:57 PM, Masahiro Yamada
[off-list ref] wrote:

2018-02-21 19:52 GMT+09:00 Arnd Bergmann [off-list ref]:

quoted

On Wed, Feb 21, 2018 at 11:20 AM, Masahiro Yamada
[off-list ref] wrote:

quoted

2018-02-21 18:56 GMT+09:00 Arnd Bergmann [off-list ref]:

quoted

On Wed, Feb 21, 2018 at 8:38 AM, Masahiro Yamada
[off-list ref] wrote:

quoted

2018-02-20 0:18 GMT+09:00 Ulf Magnusson [off-list ref]:

Hmm, I think I can implement those somehow.
But, I hope we do not have many instances like this...


If you know more naive cases, please share your knowledge.

One case that comes to mind would be architecture level selection on 32-bit
ARM, which is roughly this (I probably have some details wrong, but you
get the idea):

- older compilers don't support the latest architecture setting (-march=armv8
  or -march=armv7ve)
- newer compilers no longer support really old architectures (-march=armv4)
- setting -mthumb requires setting one of  -march=armv7-a, armv7ve, armv7-m or
  armv8 if the compiler doesn't default to those
- on a compiler that defaults to -marm, setting -march=armv7-m requires
  setting -mthumb (IIRC)
- really old compilers only support OABI, but not EABI
- newer compilers no longer support OABI
- mthumb requires EABI
- armv6 and higher are subtly broken with OABI, but only when using
  certain inline assembly with 64-bit arguments in register pairs.

I think we just shouldn't try to capture all of the above correctly in Kconfig
conditionals.

       Arnd