lkml.org 
[lkml]   [2018]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH 00/23] kconfig: move compiler capability tests to Kconfig
    On Wed, Feb 21, 2018 at 1:57 PM, Masahiro Yamada
    <yamada.masahiro@socionext.com> wrote:
    > 2018-02-21 19:52 GMT+09:00 Arnd Bergmann <arnd@arndb.de>:
    >> On Wed, Feb 21, 2018 at 11:20 AM, Masahiro Yamada
    >> <yamada.masahiro@socionext.com> wrote:
    >>> 2018-02-21 18:56 GMT+09:00 Arnd Bergmann <arnd@arndb.de>:
    >>>> On Wed, Feb 21, 2018 at 8:38 AM, Masahiro Yamada
    >>>> <yamada.masahiro@socionext.com> wrote:
    >>>>> 2018-02-20 0:18 GMT+09:00 Ulf Magnusson <ulfalizer@gmail.com>:
    >
    > 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

    \
     
     \ /
      Last update: 2018-02-21 17:04    [W:4.016 / U:0.080 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site