Re: [Buildroot] [RFC v2 01/14] arch: add hexagon architecture support

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

On Wed, 18 Dec 2024 21:30:40 -0800
Brian Cain via buildroot <buildroot@buildroot.org> wrote:

> Signed-off-by: Brian Cain <brian.cain@oss.qualcomm.com>

A non-empty commit log would be useful here, at least to introduce the
CPU architecture main characteristics, use-cases, why Buildroot matters
for this CPU architecture, etc.

> ---
>  arch/Config.in         | 10 +++++++
>  arch/Config.in.hexagon | 63 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 73 insertions(+)
>  create mode 100644 arch/Config.in.hexagon

Please add yourself as the maintainer of  this CPU architecture in the
DEVELOPERS as part of this patch. I see you did it in a separate patch,
but we like to have changes in the DEVELOPERS file together with the
commit adding the changes.

> 
> diff --git a/arch/Config.in b/arch/Config.in
> index e57f4b2baa..fe863e50a7 100644
> --- a/arch/Config.in
> +++ b/arch/Config.in
> @@ -254,6 +254,12 @@ config BR2_xtensa
>  	  http://en.wikipedia.org/wiki/Xtensa
>  	  http://www.tensilica.com/
>  
> +config BR2_hexagon

Please comply with alphabetic ordering of the CPU architectures.

> +	bool "Hexagon"
> +	select BR2_USE_MMU
> +	help
> +	  Hexagon is a Qualcomm DSP processor.
> +
>  endchoice

Another issue is that right after applying this patch, Buildroot allows
me to build an internal toolchain for this architecture (with upstream
gcc, binutils, glibc/uclibc/musl). My understanding is that this most
likely won't work, so it needs to be somehow disabled. So you need your
architecture to select BR2_ARCH_HAS_NO_TOOLCHAIN_BUILDROOT so that
building with a Buildroot toolchain is not offered.

To be honest, I am not sure we want to support an architecture that can
only be built using an external toolchain.

Also, does Hexagon has support in gcc/binutils ? Adding this new
architecture *and* supporting it only with Clang is really doing two
big things at once, which is only going to complicate stuff a lot.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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