prepended to each generated header, contains a message like
"do not edit directly - file was auto-generated by ...."
-
-
-RATIONALE:
-==========
-
-OVERVIEW OF THE CURRENT KERNEL HEADER MESS:
--------------------------------------------
-
-The original kernel headers are not easily usable from userland applications.
-they contain many declarations and construct that will result in a compilation
-failure or even worse, incorrect behaviour. for example:
-
-- some headers try to define Posix types (e.g. size_t, ssize_t) that can
- conflict with the corresponding definitions provided by your C library.
-
-- some headers use constructs that cannot be compiled in ANSI C mode.
-
-- some headers use constructs do not compile with C++ at all.
-
-- some headers contain invalid "legacy" definitions for the benefit of old
- C libraries (e.g. glibc5) but result in incorrect behaviour if used
- directly.
-
- e.g. gid_t being defined in <linux/types.h> as a 16-bit type while the
- kernel uses 32-bit ids. this results in problems when getgroups() or
- setgroups() are called, since they operate on gid_t arrays.
-
-unfortunately, these headers are also the only source of some really extensive
-constant and type definitions that are required by userland applications.
-think any library/program that need to access ALSA, or Video4Linux, or
-anything related to a specific device or Linux-specific system interface
-(e.g. IOCTLS, etc...)
-
-As a consequence, every Linux distribution provides a set of patched kernel
-headers to be used by userland applications (which installs in
-/usr/include/linux/, /usr/include/asm/, etc...). these are manually maintained
-by distribution packagers, and generated either manually or with various
-scripts. these headers are also tailored to GNU LibC and cannot be reused
-easily by Bionic.
-
-for a really long period, the kernel authors have stated that they don't want
-to fix the problem, even when someone proposed a patch to start cleaning the
-official headers. from their point of view this is purely a library author
-problem.
-
-fortunately, enlightnment happened, and the kernel now provides a way to
-install a set of "user-friendly" headers that are generated from the official
-ones by stripping the __KERNEL__ protected declarations.
-
-unfortunately, this is not enough for Bionic because the result still contains
-a few broken declarations that are difficult to route around. (see below for
-a little bit of details).
-
-we plan to be able to support these kernel-generated user-land headers in the
-future, but the priority on this issue is very low.
-
-
-WHAT WE DO:
------------
-
-so we're doomed to repeat the same effort than anyone else. the big difference
-here is that we want to automate as much as possible the generation of the
-clean headers to easily support additional architectures in the future,
-and keep current with upstream changes in the header definitions with the
-least possible hassle.
-
-of course, this is only a race to the bottom. the kernel maintainers still
-feel free to randomly break the structure of their headers (e.g. moving the
-location of some files) occasionally, so we'll need to keep up with that by
-updating our build script/original headers as these cases happen.
-
-what we do is keep a set of "original" kernel headers, and process them
-automatically to generate a set of "clean" headers that can be used from
-userland and the C library.
-
-note that the "original" headers can be tweaked a little to avoid some subtle
-issues. for example:
-
-- when the location of various USB-related headers changes in the kernel
- source tree, we want to keep them at the same location in our generated
- headers (there is no reason to break the userland API for something
- like that).
-
-- sometimes, we prefer to take certain things out of blocks guarded by a
- #ifdef __KERNEL__ .. #endif. for example, on recent kernels <linux/wireless.h>
- only includes <linux/if.h> when in kernel mode. we make it available to
- userland as well since some code out there assumes that this is the case.
-
-- sometimes, the header is simply incorrect (e.g. it uses a type without
- including the header that defines it before-hand)
-
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