Scott Anderson 52bf2d5659 Add clean kernel header for uhid.
The original kernel header was submitted in this change:

  commit 45b515c106161bb3b00d2c097504b9d44505f2d9
  Author: Scott Anderson <saa@android.com>
  Date:   Wed Aug 15 14:52:27 2012 -0700

      Add uhid original header.

      This header was cherry-picked from the upstream series that ends
      with patch adefb69b1b94df29ea2df05cd838c0e032b2c473.

      Change-Id: If516e41b6b14754e7feebdf062461dd38a31900a
      Signed-off-by: Scott Anderson <saa@android.com>

Change-Id: I088a0df4449df859835f8267d0d2e6cd4ed3c478
Signed-off-by: Scott Anderson <saa@android.com>
2012-08-16 11:56:11 -07:00
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Welcome to Bionic, Android's small and custom C library for the Android
platform.

Bionic is mainly a port of the BSD C library to our Linux kernel with the
following additions/changes:

- no support for locales
- no support for wide chars (i.e. multi-byte characters)
- its own smallish implementation of pthreads based on Linux futexes
- support for x86, ARM and ARM thumb CPU instruction sets and kernel interfaces

Bionic is released under the standard 3-clause BSD License

Bionic doesn't want to implement all features of a traditional C library, we only
add features to it as we need them, and we try to keep things as simple and small
as possible. Our goal is not to support scaling to thousands of concurrent threads
on multi-processors machines; we're running this on cell-phones, damnit !!

Note that Bionic doesn't provide a libthread_db or a libm implementation.


Adding new syscalls:
====================

Bionic provides the gensyscalls.py Python script to automatically generate syscall
stubs from the list defined in the file SYSCALLS.TXT. You can thus add a new syscall
by doing the following:

- edit SYSCALLS.TXT
- add a new line describing your syscall, it should look like:

   return_type  syscall_name(parameters)    syscall_number

- in the event where you want to differentiate the syscall function from its entry name,
  use the alternate:

   return_type  funcname:syscall_name(parameters)  syscall_number

- additionally, if the syscall number is different between ARM and x86, use:

   return_type  funcname[:syscall_name](parameters)   arm_number,x86_number

- a syscall number can be -1 to indicate that the syscall is not implemented on
  a given platform, for example:

   void   __set_tls(void*)   arm_number,-1


the comments in SYSCALLS.TXT contain more information about the line format

You can also use the 'checksyscalls.py' script to check that all the syscall
numbers you entered are correct. It does so by looking at the values defined in
your Linux kernel headers. The script indicates where the values are incorrect
and what is expected instead.