Re: [Buildroot] [PATCH next 1/1] package/rdma-core: new package

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello Julien,

On Mon, 19 Sep 2022 00:38:27 +0200
Julien Olivain <ju.o@free.fr> wrote:


> >> +The Linux Kernel needs some Infiniband configuration. In this example
> >> +the kernel "rdma_rxe" driver is needed (CONFIG_RDMA_RXE=y). See the
> >> +example fragment file provided:
> >> +
> >> +    package/rdma-core/linux-rdma.fragment  
> > 
> > Did you consider using the <pkg>_LINUX_CONFIG_FIXUPS variable instead?
> > This would make sure these configuration options are always enabled in
> > the kernel. Or is your fragment just an example?  
> 
> Yes, I considered <pkg>_LINUX_CONFIG_FIXUPS but decided not to use it.
> This fragment is really an example with the rdma_rxe driver. The
> rdma-core package could be used with any other Kernel InfiniBand
> driver. The reason I picked this one, is it's a purely software
> implementation and does not require any specific hardware to test.
> 
> The only Kernel config that could always be enabled would be
> CONFIG_INFINIBAND to enable the core support. The value would be
> limited as it would be an empty shell since no other driver/options
> would be enabled.
> 
> I could then enable a bit more kernel configs, but I think this would
> go against the Buildroot philosophy (which I could summarize as
> "Buildroot only enables the mandatory things, the user enables only
> what he/she needs/wants").
> 
> I used the word "example" for that purpose. If needed, I can clarify
> even more in the text.

Then I think there is no need to provide this example, just put the
kernel config fragment as an artifact together with the runtime test.

> >> +Buildroot package configuration
> >> +-------------------------------
> >> +
> >> +For setting up a software RoCE link, the "rdma" program is needed. It
> >> +is provided by the "iproute2" package, when "libmnl" is also
> >> +selected. Make sure to have in your Buildroot configuration:
> >> +
> >> +    BR2_PACKAGE_IPROUTE2=y
> >> +    BR2_PACKAGE_LIBMNL=y
> >> +    BR2_PACKAGE_RDMA_CORE=y  
> > 
> > Then is there a reason to not select iproute2 and libmnl? Or is it just
> > that they are needed only for specific use cases?  
> 
> Yes, the reasons are:
> - Those are indeed needed for a specific use cases,
> - Those are not mandatory dependencies (neither for build nor runtime).

OK. Then indeed, suggesting that they can be relevant (and in which
case) in the Config.in help text would be useful.

Thanks!

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