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, 348 insertions, 0 deletions

diff --git a/Documentation/input/joydev/joystick-api.rst b/Documentation/input/joydev/joystick-api.rst
new file mode 100644
index 000000000..5db6dc6fe
--- /dev/null
+++ b/Documentation/input/joydev/joystick-api.rst
@@ -0,0 +1,348 @@
+.. _joystick-api:
+
+=====================
+Programming Interface
+=====================
+
+:Author: Ragnar Hojland Espinosa <ragnar@macula.net> - 7 Aug 1998
+
+Introduction
+============
+
+.. important::
+   This document describes legacy ``js`` interface. Newer clients are
+   encouraged to switch to the generic event (``evdev``) interface.
+
+The 1.0 driver uses a new, event based approach to the joystick driver.
+Instead of the user program polling for the joystick values, the joystick
+driver now reports only any changes of its state. See joystick-api.txt,
+joystick.h and jstest.c included in the joystick package for more
+information. The joystick device can be used in either blocking or
+nonblocking mode, and supports select() calls.
+
+For backward compatibility the old (v0.x) interface is still included.
+Any call to the joystick driver using the old interface will return values
+that are compatible to the old interface. This interface is still limited
+to 2 axes, and applications using it usually decode only 2 buttons, although
+the driver provides up to 32.
+
+Initialization
+==============
+
+Open the joystick device following the usual semantics (that is, with open).
+Since the driver now reports events instead of polling for changes,
+immediately after the open it will issue a series of synthetic events
+(JS_EVENT_INIT) that you can read to obtain the initial state of the
+joystick.
+
+By default, the device is opened in blocking mode::
+
+	int fd = open ("/dev/input/js0", O_RDONLY);
+
+
+Event Reading
+=============
+
+::
+
+	struct js_event e;
+	read (fd, &e, sizeof(e));
+
+where js_event is defined as::
+
+	struct js_event {
+		__u32 time;     /* event timestamp in milliseconds */
+		__s16 value;    /* value */
+		__u8 type;      /* event type */
+		__u8 number;    /* axis/button number */
+	};
+
+If the read is successful, it will return sizeof(e), unless you wanted to read
+more than one event per read as described in section 3.1.
+
+
+js_event.type
+-------------
+
+The possible values of ``type`` are::
+
+	#define JS_EVENT_BUTTON         0x01    /* button pressed/released */
+	#define JS_EVENT_AXIS           0x02    /* joystick moved */
+	#define JS_EVENT_INIT           0x80    /* initial state of device */
+
+As mentioned above, the driver will issue synthetic JS_EVENT_INIT ORed
+events on open. That is, if it's issuing an INIT BUTTON event, the
+current type value will be::
+
+	int type = JS_EVENT_BUTTON | JS_EVENT_INIT;	/* 0x81 */
+
+If you choose not to differentiate between synthetic or real events
+you can turn off the JS_EVENT_INIT bits::
+
+	type &= ~JS_EVENT_INIT;				/* 0x01 */
+
+
+js_event.number
+---------------
+
+The values of ``number`` correspond to the axis or button that
+generated the event. Note that they carry separate numeration (that
+is, you have both an axis 0 and a button 0). Generally,
+
+        =============== =======
+	Axis		number
+        =============== =======
+	1st Axis X	0
+	1st Axis Y	1
+	2nd Axis X	2
+	2nd Axis Y	3
+	...and so on
+        =============== =======
+
+Hats vary from one joystick type to another. Some can be moved in 8
+directions, some only in 4. The driver, however, always reports a hat as two
+independent axes, even if the hardware doesn't allow independent movement.
+
+
+js_event.value
+--------------
+
+For an axis, ``value`` is a signed integer between -32767 and +32767
+representing the position of the joystick along that axis. If you
+don't read a 0 when the joystick is ``dead``, or if it doesn't span the
+full range, you should recalibrate it (with, for example, jscal).
+
+For a button, ``value`` for a press button event is 1 and for a release
+button event is 0.
+
+Though this::
+
+	if (js_event.type == JS_EVENT_BUTTON) {
+		buttons_state ^= (1 << js_event.number);
+	}
+
+may work well if you handle JS_EVENT_INIT events separately,
+
+::
+
+	if ((js_event.type & ~JS_EVENT_INIT) == JS_EVENT_BUTTON) {
+		if (js_event.value)
+			buttons_state |= (1 << js_event.number);
+		else
+			buttons_state &= ~(1 << js_event.number);
+	}
+
+is much safer since it can't lose sync with the driver. As you would
+have to write a separate handler for JS_EVENT_INIT events in the first
+snippet, this ends up being shorter.
+
+
+js_event.time
+-------------
+
+The time an event was generated is stored in ``js_event.time``. It's a time
+in milliseconds since ... well, since sometime in the past.  This eases the
+task of detecting double clicks, figuring out if movement of axis and button
+presses happened at the same time, and similar.
+
+
+Reading
+=======
+
+If you open the device in blocking mode, a read will block (that is,
+wait) forever until an event is generated and effectively read. There
+are two alternatives if you can't afford to wait forever (which is,
+admittedly, a long time;)
+
+	a) use select to wait until there's data to be read on fd, or
+	   until it timeouts. There's a good example on the select(2)
+	   man page.
+
+	b) open the device in non-blocking mode (O_NONBLOCK)
+
+
+O_NONBLOCK
+----------
+
+If read returns -1 when reading in O_NONBLOCK mode, this isn't
+necessarily a "real" error (check errno(3)); it can just mean there
+are no events pending to be read on the driver queue. You should read
+all events on the queue (that is, until you get a -1).
+
+For example,
+
+::
+
+	while (1) {
+		while (read (fd, &e, sizeof(e)) > 0) {
+			process_event (e);
+		}
+		/* EAGAIN is returned when the queue is empty */
+		if (errno != EAGAIN) {
+			/* error */
+		}
+		/* do something interesting with processed events */
+	}
+
+One reason for emptying the queue is that if it gets full you'll start
+missing events since the queue is finite, and older events will get
+overwritten.
+
+The other reason is that you want to know all that happened, and not
+delay the processing till later.
+
+Why can the queue get full? Because you don't empty the queue as
+mentioned, or because too much time elapses from one read to another
+and too many events to store in the queue get generated. Note that
+high system load may contribute to space those reads even more.
+
+If time between reads is enough to fill the queue and lose an event,
+the driver will switch to startup mode and next time you read it,
+synthetic events (JS_EVENT_INIT) will be generated to inform you of
+the actual state of the joystick.
+
+
+.. note::
+
+ As of version 1.2.8, the queue is circular and able to hold 64
+ events. You can increment this size bumping up JS_BUFF_SIZE in
+ joystick.h and recompiling the driver.
+
+
+In the above code, you might as well want to read more than one event
+at a time using the typical read(2) functionality. For that, you would
+replace the read above with something like::
+
+	struct js_event mybuffer[0xff];
+	int i = read (fd, mybuffer, sizeof(mybuffer));
+
+In this case, read would return -1 if the queue was empty, or some
+other value in which the number of events read would be i /
+sizeof(js_event)  Again, if the buffer was full, it's a good idea to
+process the events and keep reading it until you empty the driver queue.
+
+
+IOCTLs
+======
+
+The joystick driver defines the following ioctl(2) operations::
+
+				/* function			3rd arg  */
+	#define JSIOCGAXES	/* get number of axes		char	 */
+	#define JSIOCGBUTTONS	/* get number of buttons	char	 */
+	#define JSIOCGVERSION	/* get driver version		int	 */
+	#define JSIOCGNAME(len) /* get identifier string	char	 */
+	#define JSIOCSCORR	/* set correction values	&js_corr */
+	#define JSIOCGCORR	/* get correction values	&js_corr */
+
+For example, to read the number of axes::
+
+	char number_of_axes;
+	ioctl (fd, JSIOCGAXES, &number_of_axes);
+
+
+JSIOGCVERSION
+-------------
+
+JSIOGCVERSION is a good way to check in run-time whether the running
+driver is 1.0+ and supports the event interface. If it is not, the
+IOCTL will fail. For a compile-time decision, you can test the
+JS_VERSION symbol::
+
+	#ifdef JS_VERSION
+	#if JS_VERSION > 0xsomething
+
+
+JSIOCGNAME
+----------
+
+JSIOCGNAME(len) allows you to get the name string of the joystick - the same
+as is being printed at boot time. The 'len' argument is the length of the
+buffer provided by the application asking for the name. It is used to avoid
+possible overrun should the name be too long::
+
+	char name[128];
+	if (ioctl(fd, JSIOCGNAME(sizeof(name)), name) < 0)
+		strscpy(name, "Unknown", sizeof(name));
+	printf("Name: %s\n", name);
+
+
+JSIOC[SG]CORR
+-------------
+
+For usage on JSIOC[SG]CORR I suggest you to look into jscal.c  They are
+not needed in a normal program, only in joystick calibration software
+such as jscal or kcmjoy. These IOCTLs and data types aren't considered
+to be in the stable part of the API, and therefore may change without
+warning in following releases of the driver.
+
+Both JSIOCSCORR and JSIOCGCORR expect &js_corr to be able to hold
+information for all axes. That is, struct js_corr corr[MAX_AXIS];
+
+struct js_corr is defined as::
+
+	struct js_corr {
+		__s32 coef[8];
+		__u16 prec;
+		__u16 type;
+	};
+
+and ``type``::
+
+	#define JS_CORR_NONE            0x00    /* returns raw values */
+	#define JS_CORR_BROKEN          0x01    /* broken line */
+
+
+Backward compatibility
+======================
+
+The 0.x joystick driver API is quite limited and its usage is deprecated.
+The driver offers backward compatibility, though. Here's a quick summary::
+
+	struct JS_DATA_TYPE js;
+	while (1) {
+		if (read (fd, &js, JS_RETURN) != JS_RETURN) {
+			/* error */
+		}
+		usleep (1000);
+	}
+
+As you can figure out from the example, the read returns immediately,
+with the actual state of the joystick::
+
+	struct JS_DATA_TYPE {
+		int buttons;    /* immediate button state */
+		int x;          /* immediate x axis value */
+		int y;          /* immediate y axis value */
+	};
+
+and JS_RETURN is defined as::
+
+	#define JS_RETURN       sizeof(struct JS_DATA_TYPE)
+
+To test the state of the buttons,
+
+::
+
+	first_button_state  = js.buttons & 1;
+	second_button_state = js.buttons & 2;
+
+The axis values do not have a defined range in the original 0.x driver,
+except that the values are non-negative. The 1.2.8+ drivers use a
+fixed range for reporting the values, 1 being the minimum, 128 the
+center, and 255 maximum value.
+
+The v0.8.0.2 driver also had an interface for 'digital joysticks', (now
+called Multisystem joysticks in this driver), under /dev/djsX. This driver
+doesn't try to be compatible with that interface.
+
+
+Final Notes
+===========
+
+::
+
+  ____/|	Comments, additions, and specially corrections are welcome.
+  \ o.O|	Documentation valid for at least version 1.2.8 of the joystick
+   =(_)=	driver and as usual, the ultimate source for documentation is
+     U		to "Use The Source Luke" or, at your convenience, Vojtech ;)