Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 281 insertions, 0 deletions

diff --git a/Documentation/input/input.rst b/Documentation/input/input.rst
new file mode 100644
index 000000000..7bbda39d8
--- /dev/null
+++ b/Documentation/input/input.rst
@@ -0,0 +1,281 @@
+.. include:: <isonum.txt>
+
+============
+Introduction
+============
+
+:Copyright: |copy| 1999-2001 Vojtech Pavlik <vojtech@ucw.cz> - Sponsored by SuSE
+
+Architecture
+============
+
+Input subsystem is a collection of drivers that is designed to support
+all input devices under Linux. Most of the drivers reside in
+drivers/input, although quite a few live in drivers/hid and
+drivers/platform.
+
+The core of the input subsystem is the input module, which must be
+loaded before any other of the input modules - it serves as a way of
+communication between two groups of modules:
+
+Device drivers
+--------------
+
+These modules talk to the hardware (for example via USB), and provide
+events (keystrokes, mouse movements) to the input module.
+
+Event handlers
+--------------
+
+These modules get events from input core and pass them where needed
+via various interfaces - keystrokes to the kernel, mouse movements via
+a simulated PS/2 interface to GPM and X, and so on.
+
+Simple Usage
+============
+
+For the most usual configuration, with one USB mouse and one USB keyboard,
+you'll have to load the following modules (or have them built in to the
+kernel)::
+
+	input
+	mousedev
+	usbcore
+	uhci_hcd or ohci_hcd or ehci_hcd
+	usbhid
+	hid_generic
+
+After this, the USB keyboard will work straight away, and the USB mouse
+will be available as a character device on major 13, minor 63::
+
+	crw-r--r--   1 root     root      13,  63 Mar 28 22:45 mice
+
+This device is usually created automatically by the system. The commands
+to create it by hand are::
+
+	cd /dev
+	mkdir input
+	mknod input/mice c 13 63
+
+After that you have to point GPM (the textmode mouse cut&paste tool) and
+XFree to this device to use it - GPM should be called like::
+
+	gpm -t ps2 -m /dev/input/mice
+
+And in X::
+
+	Section "Pointer"
+	    Protocol    "ImPS/2"
+	    Device      "/dev/input/mice"
+	    ZAxisMapping 4 5
+	EndSection
+
+When you do all of the above, you can use your USB mouse and keyboard.
+
+Detailed Description
+====================
+
+Event handlers
+--------------
+
+Event handlers distribute the events from the devices to userspace and
+in-kernel consumers, as needed.
+
+evdev
+~~~~~
+
+``evdev`` is the generic input event interface. It passes the events
+generated in the kernel straight to the program, with timestamps. The
+event codes are the same on all architectures and are hardware
+independent.
+
+This is the preferred interface for userspace to consume user
+input, and all clients are encouraged to use it.
+
+See :ref:`event-interface` for notes on API.
+
+The devices are in /dev/input::
+
+	crw-r--r--   1 root     root      13,  64 Apr  1 10:49 event0
+	crw-r--r--   1 root     root      13,  65 Apr  1 10:50 event1
+	crw-r--r--   1 root     root      13,  66 Apr  1 10:50 event2
+	crw-r--r--   1 root     root      13,  67 Apr  1 10:50 event3
+	...
+
+There are two ranges of minors: 64 through 95 is the static legacy
+range. If there are more than 32 input devices in a system, additional
+evdev nodes are created with minors starting with 256.
+
+keyboard
+~~~~~~~~
+
+``keyboard`` is in-kernel input handler and is a part of VT code. It
+consumes keyboard keystrokes and handles user input for VT consoles.
+
+mousedev
+~~~~~~~~
+
+``mousedev`` is a hack to make legacy programs that use mouse input
+work. It takes events from either mice or digitizers/tablets and makes
+a PS/2-style (a la /dev/psaux) mouse device available to the
+userland.
+
+Mousedev devices in /dev/input (as shown above) are::
+
+	crw-r--r--   1 root     root      13,  32 Mar 28 22:45 mouse0
+	crw-r--r--   1 root     root      13,  33 Mar 29 00:41 mouse1
+	crw-r--r--   1 root     root      13,  34 Mar 29 00:41 mouse2
+	crw-r--r--   1 root     root      13,  35 Apr  1 10:50 mouse3
+	...
+	...
+	crw-r--r--   1 root     root      13,  62 Apr  1 10:50 mouse30
+	crw-r--r--   1 root     root      13,  63 Apr  1 10:50 mice
+
+Each ``mouse`` device is assigned to a single mouse or digitizer, except
+the last one - ``mice``. This single character device is shared by all
+mice and digitizers, and even if none are connected, the device is
+present.  This is useful for hotplugging USB mice, so that older programs
+that do not handle hotplug can open the device even when no mice are
+present.
+
+CONFIG_INPUT_MOUSEDEV_SCREEN_[XY] in the kernel configuration are
+the size of your screen (in pixels) in XFree86. This is needed if you
+want to use your digitizer in X, because its movement is sent to X
+via a virtual PS/2 mouse and thus needs to be scaled
+accordingly. These values won't be used if you use a mouse only.
+
+Mousedev will generate either PS/2, ImPS/2 (Microsoft IntelliMouse) or
+ExplorerPS/2 (IntelliMouse Explorer) protocols, depending on what the
+program reading the data wishes. You can set GPM and X to any of
+these. You'll need ImPS/2 if you want to make use of a wheel on a USB
+mouse and ExplorerPS/2 if you want to use extra (up to 5) buttons.
+
+joydev
+~~~~~~
+
+``joydev`` implements v0.x and v1.x Linux joystick API. See
+:ref:`joystick-api` for details.
+
+As soon as any joystick is connected, it can be accessed in /dev/input on::
+
+	crw-r--r--   1 root     root      13,   0 Apr  1 10:50 js0
+	crw-r--r--   1 root     root      13,   1 Apr  1 10:50 js1
+	crw-r--r--   1 root     root      13,   2 Apr  1 10:50 js2
+	crw-r--r--   1 root     root      13,   3 Apr  1 10:50 js3
+	...
+
+And so on up to js31 in legacy range, and additional nodes with minors
+above 256 if there are more joystick devices.
+
+Device drivers
+--------------
+
+Device drivers are the modules that generate events.
+
+hid-generic
+~~~~~~~~~~~
+
+``hid-generic`` is one of the largest and most complex driver of the
+whole suite. It handles all HID devices, and because there is a very
+wide variety of them, and because the USB HID specification isn't
+simple, it needs to be this big.
+
+Currently, it handles USB mice, joysticks, gamepads, steering wheels,
+keyboards, trackballs and digitizers.
+
+However, USB uses HID also for monitor controls, speaker controls, UPSs,
+LCDs and many other purposes.
+
+The monitor and speaker controls should be easy to add to the hid/input
+interface, but for the UPSs and LCDs it doesn't make much sense. For this,
+the hiddev interface was designed. See Documentation/hid/hiddev.rst
+for more information about it.
+
+The usage of the usbhid module is very simple, it takes no parameters,
+detects everything automatically and when a HID device is inserted, it
+detects it appropriately.
+
+However, because the devices vary wildly, you might happen to have a
+device that doesn't work well. In that case #define DEBUG at the beginning
+of hid-core.c and send me the syslog traces.
+
+usbmouse
+~~~~~~~~
+
+For embedded systems, for mice with broken HID descriptors and just any
+other use when the big usbhid wouldn't be a good choice, there is the
+usbmouse driver. It handles USB mice only. It uses a simpler HIDBP
+protocol. This also means the mice must support this simpler protocol. Not
+all do. If you don't have any strong reason to use this module, use usbhid
+instead.
+
+usbkbd
+~~~~~~
+
+Much like usbmouse, this module talks to keyboards with a simplified
+HIDBP protocol. It's smaller, but doesn't support any extra special keys.
+Use usbhid instead if there isn't any special reason to use this.
+
+psmouse
+~~~~~~~
+
+This is driver for all flavors of pointing devices using PS/2
+protocol, including Synaptics and ALPS touchpads, Intellimouse
+Explorer devices, Logitech PS/2 mice and so on.
+
+atkbd
+~~~~~
+
+This is driver for PS/2 (AT) keyboards.
+
+iforce
+~~~~~~
+
+A driver for I-Force joysticks and wheels, both over USB and RS232.
+It includes Force Feedback support now, even though Immersion
+Corp. considers the protocol a trade secret and won't disclose a word
+about it.
+
+Verifying if it works
+=====================
+
+Typing a couple keys on the keyboard should be enough to check that
+a keyboard works and is correctly connected to the kernel keyboard
+driver.
+
+Doing a ``cat /dev/input/mouse0`` (c, 13, 32) will verify that a mouse
+is also emulated; characters should appear if you move it.
+
+You can test the joystick emulation with the ``jstest`` utility,
+available in the joystick package (see :ref:`joystick-doc`).
+
+You can test the event devices with the ``evtest`` utility.
+
+.. _event-interface:
+
+Event interface
+===============
+
+You can use blocking and nonblocking reads, and also select() on the
+/dev/input/eventX devices, and you'll always get a whole number of input
+events on a read. Their layout is::
+
+    struct input_event {
+	    struct timeval time;
+	    unsigned short type;
+	    unsigned short code;
+	    int value;
+    };
+
+``time`` is the timestamp, it returns the time at which the event happened.
+Type is for example EV_REL for relative movement, EV_KEY for a keypress or
+release. More types are defined in include/uapi/linux/input-event-codes.h.
+
+``code`` is event code, for example REL_X or KEY_BACKSPACE, again a complete
+list is in include/uapi/linux/input-event-codes.h.
+
+``value`` is the value the event carries. Either a relative change for
+EV_REL, absolute new value for EV_ABS (joysticks ...), or 0 for EV_KEY for
+release, 1 for keypress and 2 for autorepeat.
+
+See :ref:`input-event-codes` for more information about various event codes.