[PATCH 00/15] mach/io.h cleanup and removal

On 02/14/2012 03:26 PM, Arnd Bergmann wrote:

On Tuesday 14 February 2012, Tony Lindgren wrote:

quoted

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c) Don't allow mach includes in drivers and sound dirs for
multi-platform kernels. This is already the case for any multi-arch
driver. A lot of the headers are platform_data structs or things that
should be cleaned up or need common infrastructure. Some cases I've
found seem like the include is unnecessary. Also, just fixing up the
name or path is no guarantee of avoiding namespace collisions.

Out of the three options c) makes most sense for multi-subarch kernels.
And that avoids having to sort out the name collisions with defines.

I agree that this is the ideal, but as far as I can tell, we have a
significant amount of functions that are defined in platform specific
code but used in platform specific drivers. E.g. when you have a
piece of code dealing with system management registers in your platform,
that would be used in the cpufreq, irqchip, watchdog and more drivers.

From my quick survey, those categories are really the exception. I would

guess platform_data structs is at least half of it. Older platforms seem
to be another big chunk.

Lack of a common usb phy infrastructure is another example of custom
platform functions (tegra usb_phy.h).

There has to be some place where we can put function declarations
for stuff like this, while at the same time we should try to minimise
the amount that is required.

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For dealing with legacy platforms, I too would prefer b).

How about this:

* We stop providing arch/arm/{mach,plat}-*/include/ to C files
outside of arch/arm/{mach,plat}-* when CONFIG_MULTIPLATFORM is
enabled.

* Any symbol that is required to be visible in device drivers
gets declared in arch/arm/include/mach-*/*.h, but we are very
careful about adding only the absolute minimum here.

Why not include/linux? Any includes for drivers which are either
multiple arches (ahci_platform.h) or multiple ARM machines
(linux/amba/pl061.h) are already there. Every platform trying to dump
dozens of includes there would certainly get attention and force some
clean-up.

Rob