Re: [GIT PULL] pin control bulk changes for v4.16

[Linus Walleij]

On Sat, Feb 3, 2018 at 1:51 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Feb 2, 2018 at 4:44 PM, Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> Stupid patch attached. I don't know how much this helps the insane
>> dependency hell for <linux/pinctrl/devinfo.h>, but it's bound to help
>> _some_.
>
> Testing it, that patch definitely cuts down on recompiles after
>
>      touch include/linux/pinctrl/devinfo.h
>
> a lot.

Hey very nice. Sorry I was offline this weekend and didn't provide
much feedback.

Indeed it is smarter to forward-declare struct dev_pin_info.

I rebuilt my platforms with the mainline and all is working just fine
of course.

> It still ends up rebuilding a fair amount of odd drivers, but now the
> files it rebuilds at least make _some_ sense.

Yeah :/

I guess the lesson learned is that when I push stuff into device
core like this, it needs to be done as exquisitely as cache-aligned
structs because of the overall impact on the build systems.

> One odd header include down. Ten million to go.

Sorry about contributing to that :(

Another thing that comes to mind was Paul Gortmaker's tedious
work to remove #include <linux/module.h> from drivers that cannot
be built as modules that happened in the last few months. My
subsystems had a few of those and it visibly impacted build
time. As usual clean and consistent code is code that compiles
quickly...

We definitely need some better tooling to find these things,
using Ingo's head and your occasional frustration is not going to
scale.

Julia: do you have ideas on tooling that can loosen #include
deps and advise on when to replace #includes with forward
declarations of structs (etc) to bring down rebuild-triggering
dependencies?

Yours,
Linus Walleij