Date:   Mon, 17 Jul 2023 09:59:52 -0600
From:   Rob Herring <robh@...nel.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
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        Pengutronix Kernel Team <kernel@...gutronix.de>,
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        chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
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Subject: Re: [PATCH] pwm: Explicitly include correct DT includes

On Mon, Jul 17, 2023 at 1:44 AM Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
>
> On Fri, Jul 14, 2023 at 11:48:50AM -0600, Rob Herring wrote:
> > The DT of_device.h and of_platform.h date back to the separate
> > of_platform_bus_type before it as merged into the regular platform bus.
> > As part of that merge prepping Arm DT support 13 years ago, they
> > "temporarily" include each other. They also include platform_device.h
> > and of.h. As a result, there's a pretty much random mix of those include
> > files used throughout the tree. In order to detangle these headers and
> > replace the implicit includes with struct declarations, users need to
> > explicitly include the correct includes.
>
> so the eventual goal here is to prepare for:
>
>  - drop #include <linux/of_device.h> from include/linux/of_platform.h
>  - drop #include <linux/of.h> from include/linux/of_device.h
>  - drop #include <linux/of_platform.h> from include/linux/of_device.h
>  - drop #include <linux/platform_device.h> from include/linux/of_device.h
>  - drop #include <linux/platform_device.h> from include/linux/of_platform.h

Yes.

> > Signed-off-by: Rob Herring <robh@...nel.org>
> > ---
> >  drivers/pwm/core.c               | 1 +
> >  drivers/pwm/pwm-apple.c          | 1 +
> >  drivers/pwm/pwm-atmel-hlcdc.c    | 1 +
> >  drivers/pwm/pwm-atmel-tcb.c      | 3 +--
> >  drivers/pwm/pwm-atmel.c          | 1 -
> >  drivers/pwm/pwm-berlin.c         | 1 +
> >  drivers/pwm/pwm-cros-ec.c        | 1 +
> >  drivers/pwm/pwm-fsl-ftm.c        | 3 +--
> >  drivers/pwm/pwm-hibvt.c          | 2 +-
> >  drivers/pwm/pwm-imx1.c           | 1 -
> >  drivers/pwm/pwm-jz4740.c         | 2 +-
> >  drivers/pwm/pwm-lp3943.c         | 1 +
> >  drivers/pwm/pwm-lpc18xx-sct.c    | 1 +
> >  drivers/pwm/pwm-mediatek.c       | 1 -
> >  drivers/pwm/pwm-meson.c          | 1 -
> >  drivers/pwm/pwm-microchip-core.c | 2 +-
> >  drivers/pwm/pwm-mtk-disp.c       | 1 -
> >  drivers/pwm/pwm-pxa.c            | 1 +
> >  drivers/pwm/pwm-sifive.c         | 1 +
> >  drivers/pwm/pwm-sl28cpld.c       | 1 +
> >  drivers/pwm/pwm-sprd.c           | 1 +
> >  drivers/pwm/pwm-sun4i.c          | 1 -
> >  drivers/pwm/pwm-sunplus.c        | 1 +
> >  drivers/pwm/pwm-tegra.c          | 1 -
> >  drivers/pwm/pwm-tiecap.c         | 2 +-
> >  drivers/pwm/pwm-tiehrpwm.c       | 2 +-
> >  drivers/pwm/pwm-visconti.c       | 2 +-
> >  drivers/pwm/pwm-vt8500.c         | 5 +----
> >  28 files changed, 21 insertions(+), 21 deletions(-)
> >
> > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > index 3dacceaef4a9..d37617c60eae 100644
> > --- a/drivers/pwm/core.c
> > +++ b/drivers/pwm/core.c
> > @@ -8,6 +8,7 @@
> >
> >  #include <linux/acpi.h>
> >  #include <linux/module.h>
> > +#include <linux/of.h>
> >  #include <linux/pwm.h>
> >  #include <linux/radix-tree.h>
> >  #include <linux/list.h>
>
> This file includes neither of_device.h nor of_platform.h and up to now
> gets of.h via <linux/pwm.h>.

Indeed.

> What is your plan for <linux/pwm.h>'s include? I think it would only need
>
>         struct of_phandle_args;

Here's what I'm testing with:

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 04ae1d9073a7..5a59a7d53be8 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -4,8 +4,10 @@

 #include <linux/err.h>
 #include <linux/mutex.h>
-#include <linux/of.h>

+struct device;
+struct fwnode_handle;
+struct of_phandle_args;
 struct pwm_chip;

 /**

>
> to replace that. (But that would need another patch like this one, as
> then e.g. drivers/pwm/pwm-sl28cpld.c fails to compile because
> device_property_read_u32() is undeclared. It would need to #include
> <linux/property.h> which now it gets transitively via <linux/of.h>.)

property.h is added in this patch, so it should be okay?

> If <linux/pwm.h> is planed to continue #including <linux/of.h>, the
> explicit include here isn't necessary (and probably elsewhere).

I would like to drop including of.h, but probably not this cycle.
Either way, I thought kernel best practice was to not rely on implicit
includes.

BTW, linux/i2c.h is another source of lots of implicit of.h includes.
That one looks like we can't get rid of.

> I don't care much either way, but maybe your quest would be a bit
> simpler if you only touch files that include the two files you want to
> modify?

Yes, that's how it started. I kind of decided it wasn't worth trying
to split things up by every separate reason explicit includes were not
correct.

>
> *shrug*, this patch is still an improvement so:
>
> Acked-by: Uwe Kleine-Köng <u.kleine-koenig@...gutronix.de>
>
> Another thing I wonder is: How did you identify the files that need
> these includes. I guess you have a list of types for each header and
> search for files that use any of the types but doesn't include the
> respecitve header? I wonder if tracking this type -> header mapping in
> machine readable form somewhere would be nice, to e.g. make checkpatch
> warn if a file uses struct of_node but only gets it by chance?

It's been less automated than I'd like. It's been a lot of grepping
with a list of symbols the headers provide. For example, I get all the
files including of_device.h and then get the ones with no symbols from
of_device.h. And then do a manual review of what are the correct
headers for the file. And then run thru builds and fix all the issues.

Rob

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