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pinctrl: remove include file from <linux/device.h>

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When pulling the recent pinctrl merge, I was surprised by how a
pinctrl-only pull request ended up rebuilding basically the whole
kernel.

The reason for that ended up being that <linux/device.h> included
<linux/pinctrl/devinfo.h>, so any change to that file ended up causing
pretty much every driver out there to be rebuilt.

The reason for that was because 'struct device' has this in it:

    #ifdef CONFIG_PINCTRL
        struct dev_pin_info     *pins;
    #endif

but we already avoid header includes for these kinds of things in that
header file, preferring to just use a forward-declaration of the
structure instead.  Exactly to avoid this kind of header dependency.

Since some drivers seem to expect that <linux/pinctrl/devinfo.h> header
to come in automatically, move the include to <linux/pinctrl/pinctrl.h>
instead.  It might be better to just make the includes more targeted,
but I'm not going to review every driver.

It would definitely be good to have a tool for finding and minimizing
header dependencies automatically - or at least help with them.  Right
now we almost certainly end up having way too many of these things, and
it's hard to test every single configuration.

FWIW, you can get a sense of the "hotness" of a header file with something
like this after doing a full build:

    find . -name '.*.o.cmd' -print0 |
        xargs -0 tail --lines=+2 |
        grep -v 'wildcard ' |
        tr ' \\' '\n' |
        sort | uniq -c | sort -n | less -S

which isn't exact (there are other things in those '*.o.cmd' than just
the dependencies, and the "--lines=+2" only removes the header), but
might a useful approximation.

With this patch, <linux/pinctrl/devinfo.h> drops to "only" having 833
users in the current x86-64 allmodconfig.  In contrast, <linux/device.h>
has 14857 build files including it directly or indirectly.

Of course, the headers that absolutely _everybody_ includes (things like
<linux/types.h> etc) get a score of 23000+.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2018-02-02 16:44:14 -08:00
parent d3581c8ef7
commit 23c35f48f5
2 changed files with 2 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/device.h
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@ -20,7 +20,6 @@
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/pinctrl/devinfo.h>
#include <linux/pm.h>
#include <linux/atomic.h>
#include <linux/ratelimit.h>
@ -41,6 +40,7 @@ struct fwnode_handle;
struct iommu_ops;
struct iommu_group;
struct iommu_fwspec;
struct dev_pin_info;
struct bus_attribute {
struct attribute attr;

1
include/linux/pinctrl/pinctrl.h
View File

@ -18,6 +18,7 @@
#include <linux/list.h>
#include <linux/seq_file.h>
#include <linux/pinctrl/pinctrl-state.h>
#include <linux/pinctrl/devinfo.h>
struct device;
struct pinctrl_dev;