Pass user defines for Barebox build

[Ahmad Fatoum]

Hi,

On 29.11.23 11:13, Lior Weintraub wrote:
> Thanks Ahmad,
> 
> On our Barebox porting we have a small piece of code that needs different coding if we build it for QEMU or for the real HW.
> We are used to pass build defines in other projects so that is way we took this approach.  
> 
> I assume the official way would be to set a new defconfig and define a new platform?
> Currently our spider_defconfig has:
> CONFIG_MACH_SPIDER_MK1_EVK=y
> So the new one (spider-qemu_defconfig) would use:
> CONFIG_MACH_SPIDER_QEMU_EVK=y  
> 
> Is this the correct solution?

I'd rather suggest either

   - Having the difference detected at runtime.

   - Have the difference encoded into the device tree: You can have
     multiple ENTRY_FUNCTION, each with a different device tree and
     get multiple images in the same build, one for each device tree.

This avoids the confusion when the wrong image is used. You can even
combine them, see for example arch/arm/boards/stm32mp15xx-dkx/lowlevel.c.

Cheers,
Ahmad

> 
> Cheers,
> Lior.
> 
>> -----Original Message-----
>> From: Ahmad Fatoum <a.fatoum at pengutronix.de>
>> Sent: Wednesday, November 29, 2023 9:20 AM
>> To: Lior Weintraub <liorw at pliops.com>; barebox at lists.infradead.org
>> Subject: Re: Pass user defines for Barebox build
>>
>> CAUTION: External Sender
>>
>> Hello Lior,
>>
>> On 27.11.23 08:02, Lior Weintraub wrote:
>>> Hi guys,
>>>
>>> Is there a formal way to pass user compilation flags into Barebox build?
>>
>> There isn't. Both barebox and Linux have been broken in the past by distros
>> setting CFLAGS that force hardening options that require kernel/libc cooperation,
>> which didn't apply to barebox. For that reason, the variables were prefixed
>> with KBUILD_ and a way to inject variables into the build of barebox itself
>> (i.e. not host tools) is intentionally not provided.
>>
>> What options do you want to inject?
>>
>>> I couldn't find one so I just patched the main Makefile
>>> diff --git a/Makefile b/Makefile
>>> index 471bbc2679..febc94b7f3 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -443,7 +443,7 @@ KBUILD_CPPFLAGS        := -D__KERNEL__ -
>> D__BAREBOX__ $(LINUXINCLUDE) -fno-builti
>>>  KBUILD_CFLAGS   := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs
>> \
>>>                    -fno-strict-aliasing -fno-common -fshort-wchar \
>>>                     -Werror=implicit-function-declaration -Werror=implicit-int \
>>> -                   -Os -pipe -Wmissing-prototypes -std=gnu89
>>> +                   -Os -pipe -Wmissing-prototypes -std=gnu89
>> $(BAREBOX_USER_CFLAGS)
>>
>> USER is an unfortunate name, because there's already KBUILD_USERCFLAGS
>> and that user is short for userspace and not the user, who is building
>> barebox.
>>
>> Cheers,
>> Ahmad
>>
>>>  KBUILD_AFLAGS          := -D__ASSEMBLY__
>>>  KBUILD_AFLAGS_KERNEL :=
>>>  KBUILD_CFLAGS_KERNEL :=
>>>
>>> This patch allowed me to set BAREBOX_CFLAGS environment when calling
>> make.
>>>
>>> Thanks,
>>> Lior.
>>>
>>>
>>>
>>
>> --
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> 

-- 
Pengutronix e.K.                           |                             |
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