staging: android: logger: Allow to completely disable

* Logger is completely disabled on kernel_common branch.
* Let's disable it via userspace and give option to
  user to re-enable it when required.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: logger: Allocate logs dynamically at boot (v3)

This changes the log initialization to be dynamic, but still
at boot time.  These changes are a predecessor to implementing
runtime allocation and freeing of logs, to make the Android logger
less hard-coded.

Change from a fixed set of static log structures, to allocation
at init time into a list.  Return proper error numbers on log
allocation failure.

Cc: Brian Swetland <swetland@google.com>
Signed-off-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: Android: Fix some checkpatch warnings

Warnings reported by checkpatch.pl have been fixed.

Cc: Brian Swetland <swetland@google.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: logger: Finish documentation of two structs
Signed-off-by: Cruz Julian Bishop <cruzjbishop@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: logger: Fix some sparse and whitespace issues

Fix a few sparse warnings, and improve whitespace.

Cc: Brian Swetland <swetland@google.com>
Signed-off-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: logger: enforce GID and CAP check on log flush
Restrict log flushing to those in the logs group, or
anyone with CAP_SYSLOG.

Cc: Android Kernel Team <kernel-team@android.com>
Cc: Charndeep Grewal <csgrewa@tycho.ncsc.mil>
Signed-off-by: Charndeep Grewal <csgrewa@tycho.ncsc.mil>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Staging: Android: logger: module_exit implementation

This patch creates the module_exit for the android logger
so that it can be loaded and unloaded as a module.

The android logger is already declared as a tristate in the
Kconfig but the module_exit function was missing.

device_initcall works also with modprobe since include/linux/init.h:

 #define module_init(x)  __initcall(x);
 ...
 #define __initcall(fn) device_initcall(fn)

Signed-off-by: Luca Clementi <luca.clementi@gmail.com>
Cc: Brian Swetland <swetland@google.com>
Cc: Robert Love <rlove@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: logger: Correct write offset reset on error
In the situation that a writer fails to copy data from userspace it will reset
the write offset to the value it had before it went to sleep. This discarding
any messages written while aquiring the mutex.

Therefore the reset offset needs to be retrieved after acquiring the mutex.

Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: android: fix a possible memory leak

Memory allocated by kstrdup should be freed.

CC: Brian Swetland <swetland@google.com>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Seunghun Lee <waydi1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: android: logger: fixed checkpatch.pl warnings.
Signed-off-by: Jerry Stralko <gerb.stralko@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
backport rwsem from Linux 3.11
mainly to add writer lock stealing by Alex Shi and later improvements
by Michael Lespinasse
http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/log/lib/rwsem.c?h=linux-3.11.y
Optimized ARM RWSEM algorithm
RWSEM implementation for ARM using atomic functions.
Heavily based on arch/sh/include/asm/rwsem.h

Signed-off-by: Ashwin Chaugule <ashwinc@codeaurora.org>