Re: [PATCH 2/3] x86: apuv2: fix input dependencies

Re: [PATCH 2/3] x86: apuv2: fix input dependencies

[Enrico Weigelt, metux IT consult]

On 05.03.19 09:23, Arnd Bergmann wrote:

(CC'ing kbuild maintainer + list, hoping for better ideas :)


> No, that wouldn't be good here. In effect that means that with INPUT disabled,
> most of the x86 platform drivers are disabled, until you enable the
> PCENGINES_APU2 symbol, which then ends up showing all the other
> symbols at once, and changing them to their default states.

Okay, I didn't consider the defaults.

Maybe we should talk about step by step getting away from these defaults
(perhaps move them to the defconfigs ?) on a broader scale ... but yeah,
that's far out of scope now.

So, you've conviced me.
Add me to Reviewed-By to your patches and forget about mine.

> Another problem is that you likely run into circular dependency chains
> after trying that. The best practice for select vs. depends are

hmm, if circular deps happen, wouldn't that mean we've got some deeper
problems in here ? IMHO, dependencies should always form a DAG (except
for some really rare cases).

Do you recall any actual problem w/ input vs gpio vs. drivers ?
I'd like to have a closer look at it.

> 1. try to use 'depends on' if you can

Well, this has the unpleasant side effect that we often have to enable
a lot of things, just to even see the individual driver. For people who
just wanna configure a kernel for their board, this is a bit nasty.

But, okay, I'm going to do this w/ my own tool - I've written a small
tool that allows easy kernel reconfiguration on a higher level: you
can just pick some board templates and enable high level features like
eth, gpu, etc - it automatically creates a .config for you. I'm going
announce it on lkml soon.


--mtx

-- 
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287

Re: [PATCH 2/3] x86: apuv2: fix input dependencies

[Andy Shevchenko]

On Tue, Mar 5, 2019 at 3:50 PM Enrico Weigelt, metux IT consult
<lkml@metux.net> wrote:
> On 05.03.19 09:23, Arnd Bergmann wrote:

> > 1. try to use 'depends on' if you can
>
> Well, this has the unpleasant side effect that we often have to enable
> a lot of things, just to even see the individual driver. For people who
> just wanna configure a kernel for their board, this is a bit nasty.
>
> But, okay, I'm going to do this w/ my own tool - I've written a small
> tool that allows easy kernel reconfiguration on a higher level: you
> can just pick some board templates and enable high level features like
> eth, gpu, etc - it automatically creates a .config for you. I'm going
> announce it on lkml soon.

Darren gave a talk about merging kernel configs to get something like
you want to.
This tool is quite long already lying around. merge_config.sh in your
kernel source tree.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/3] x86: apuv2: fix input dependencies

[Enrico Weigelt, metux IT consult]

On 05.03.19 14:56, Andy Shevchenko wrote:
> 
> Darren gave a talk about merging kernel configs to get something like
> you want to.
> This tool is quite long already lying around. merge_config.sh in your
> kernel source tree.

Yes, that's similar to how some distros (eg. yocto) do it.

But my requirements are a bit more complex:

In my final meta-config, I just wanna say:

* i have board A (possibly multiple boards)
* i need features X, Y, Z (eg. eth, display, can, ext4, acl, ...)

And that shall be all to generate a minimal config for exactly those
requirements.

Doing that by just putting config snippets together, quickly turns into
a maintenance hell. At least you'd need recursive dependencies and some
if/else logic.

That's why I've written kmct:

https://github.com/metux/kmct


--mtx

-- 
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287

Re: [PATCH 2/3] x86: apuv2: fix input dependencies

[Darren Hart]

On Thu, Mar 07, 2019 at 01:10:13AM +0100, Enrico Weigelt, metux IT consult wrote:
> On 05.03.19 14:56, Andy Shevchenko wrote:
> > 
> > Darren gave a talk about merging kernel configs to get something like
> > you want to.
> > This tool is quite long already lying around. merge_config.sh in your
> > kernel source tree.
> 
> Yes, that's similar to how some distros (eg. yocto) do it.
> 

I wrote merge_config.sh to replace and simplify some of the yocto
tooling. With merge_config upstream, Yocto now uses it directly.

> But my requirements are a bit more complex:
> 
> In my final meta-config, I just wanna say:
> 
> * i have board A (possibly multiple boards)
> * i need features X, Y, Z (eg. eth, display, can, ext4, acl, ...)
> 
> And that shall be all to generate a minimal config for exactly those
> requirements.

That's also the goal of the Yocto configuration fragments, and is
possible with merge_config with a set of defined fragments.

> 
> Doing that by just putting config snippets together, quickly turns into
> a maintenance hell. At least you'd need recursive dependencies and some
> if/else logic.
> 
> That's why I've written kmct:
> 
> https://github.com/metux/kmct

I had a look, the README could benefit from a basic usage example.
Digging through it further, it appears that you are creating yaml files
which contain CONFIGs. The problem with this in my opinion is these are
kernel version specific, so you know have a lot of boiler plate yaml
wrapping kernel version specific CONFIG options which will slowly get
out of sync over time. This is the usual argument for keeping config
fragments together with the kernel - and why we do that in arch/*/config
for example.

Perhaps I'm missing your desired workflow though. I tend to find the
options I need and record them in a fragment, and save it off for later
to quickly be able to "make defconfig fragA.config fragB.config" etc. Is
what you're trying to do different?

-- 
Darren Hart
VMware Open Source Technology Center

Re: [PATCH 2/3] x86: apuv2: fix input dependencies

[Arnd Bergmann]

On Tue, Mar 5, 2019 at 2:50 PM Enrico Weigelt, metux IT consult
<lkml@metux.net> wrote:
>
> On 05.03.19 09:23, Arnd Bergmann wrote:
>
> hmm, if circular deps happen, wouldn't that mean we've got some deeper
> problems in here ? IMHO, dependencies should always form a DAG (except
> for some really rare cases).
>
> Do you recall any actual problem w/ input vs gpio vs. drivers ?
> I'd like to have a closer look at it.

Not with gpio. Most of the circular dependencies I've seen tend to
revolve around drivers/gpu/drm, which uses more 'select' statements
than most other subsystems. Those dependencies often touch
backlight, acpi, fbdev and other things then.

       Arnd