linux-kernel - Re: [PATCH v2] codafs: Fix build using bare-metal toolchain

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Date:   Wed, 21 Nov 2018 17:48:59 -0500
From:   Jan Harkes <jaharkes@...cmu.edu>
To:     Sam Protsenko <semen.protsenko@...aro.org>
CC:     hch@....de, Andrew Morton <akpm@...ux-foundation.org>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-scsi@...r.kernel.org, Praneeth Bajjuri <praneeth@...com>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v2] codafs: Fix build using bare-metal toolchain

That actually makes a lot of sense.

Jan

On November 21, 2018 2:39:03 PM EST, Sam Protsenko <semen.protsenko@...aro.org> wrote:
>+ Jan Harkes back to "To:" list, slipped away somehow...
>
>On Wed, Nov 21, 2018 at 9:36 PM Sam Protsenko
><semen.protsenko@...aro.org> wrote:
>>
>> On Wed, Nov 21, 2018 at 8:10 PM Jan Harkes <jaharkes@...cmu.edu>
>wrote:
>> >
>> > On Wed, Nov 21, 2018 at 06:41:13PM +0200, Andy Shevchenko wrote:
>> > > I'm not sure how you managed to miss people in this list (perhaps
>by
>> > > default you have suppress all Cc in your Git configuration), but
>I
>> > > guess we may gently ask Christoph to apply this in case Jan will
>not
>> > > appear.
>> >
>> > You have got to give me a little more than 10 minutes to respond
>before
>> > assuming that I would not appear... I don't think I've ignored any
>> > previous emails on this subject and the only issues has been some
>people
>> > not receiving my responses for unknown reasons (agressive spam
>filter?).
>> >
>> > I have no problem with this patch, have it sitting with some other
>> > non-urgent patches and in case it doesn't appear upstream it should
>> > piggyback with whatever I have to send.
>> >
>>
>> Thanks, Jan, really appreciate it. We need this patch to fix our
>tests
>> with allmodconfig configuration (in Linaro CI loops).
>>
>> > I still don't know why the bare-metal toolchain couldn't just add a
>> > -D__linux__.  I understand that this define is expected to be
>always
>> > present while compiling kernel headers so that there is no good
>reason
>> > to even bother testing for it, which is why I have no issue with
>the
>> > patch. But it seems it would make your life a lot easier if you had
>it
>> > defined.
>> >
>>
>> As I understand it, from toolchain's point of view, if __linux__ is
>> defined then it means that the program is being built *for* Linux
>> (i.e. we can use Linux specific features, ABI, like syscalls).
>> Checking this definition can make sense in uapi headers, but in
>kernel
>> code we shouldn't use it (as kernel is baremetal program and not
>> compiled for some OS). I presume that's why __linux__ is not defined
>> in bare-metal toolchains (as those don't provide Linux specific
>> features, libc, etc).
>>
>> > Jan
>> >