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, 156 insertions, 0 deletions

diff --git a/Documentation/i2c/functionality.rst b/Documentation/i2c/functionality.rst
new file mode 100644
index 000000000..377507c56
--- /dev/null
+++ b/Documentation/i2c/functionality.rst
@@ -0,0 +1,156 @@
+=======================
+I2C/SMBus Functionality
+=======================
+
+INTRODUCTION
+------------
+
+Because not every I2C or SMBus adapter implements everything in the
+I2C specifications, a client can not trust that everything it needs
+is implemented when it is given the option to attach to an adapter:
+the client needs some way to check whether an adapter has the needed
+functionality.
+
+
+FUNCTIONALITY CONSTANTS
+-----------------------
+
+For the most up-to-date list of functionality constants, please check
+<uapi/linux/i2c.h>!
+
+  =============================== ==============================================
+  I2C_FUNC_I2C                    Plain i2c-level commands (Pure SMBus
+                                  adapters typically can not do these)
+  I2C_FUNC_10BIT_ADDR             Handles the 10-bit address extensions
+  I2C_FUNC_PROTOCOL_MANGLING      Knows about the I2C_M_IGNORE_NAK,
+                                  I2C_M_REV_DIR_ADDR and I2C_M_NO_RD_ACK
+                                  flags (which modify the I2C protocol!)
+  I2C_FUNC_NOSTART                Can skip repeated start sequence
+  I2C_FUNC_SMBUS_QUICK            Handles the SMBus write_quick command
+  I2C_FUNC_SMBUS_READ_BYTE        Handles the SMBus read_byte command
+  I2C_FUNC_SMBUS_WRITE_BYTE       Handles the SMBus write_byte command
+  I2C_FUNC_SMBUS_READ_BYTE_DATA   Handles the SMBus read_byte_data command
+  I2C_FUNC_SMBUS_WRITE_BYTE_DATA  Handles the SMBus write_byte_data command
+  I2C_FUNC_SMBUS_READ_WORD_DATA   Handles the SMBus read_word_data command
+  I2C_FUNC_SMBUS_WRITE_WORD_DATA  Handles the SMBus write_byte_data command
+  I2C_FUNC_SMBUS_PROC_CALL        Handles the SMBus process_call command
+  I2C_FUNC_SMBUS_READ_BLOCK_DATA  Handles the SMBus read_block_data command
+  I2C_FUNC_SMBUS_WRITE_BLOCK_DATA Handles the SMBus write_block_data command
+  I2C_FUNC_SMBUS_READ_I2C_BLOCK   Handles the SMBus read_i2c_block_data command
+  I2C_FUNC_SMBUS_WRITE_I2C_BLOCK  Handles the SMBus write_i2c_block_data command
+  =============================== ==============================================
+
+A few combinations of the above flags are also defined for your convenience:
+
+  =========================       ======================================
+  I2C_FUNC_SMBUS_BYTE             Handles the SMBus read_byte
+                                  and write_byte commands
+  I2C_FUNC_SMBUS_BYTE_DATA        Handles the SMBus read_byte_data
+                                  and write_byte_data commands
+  I2C_FUNC_SMBUS_WORD_DATA        Handles the SMBus read_word_data
+                                  and write_word_data commands
+  I2C_FUNC_SMBUS_BLOCK_DATA       Handles the SMBus read_block_data
+                                  and write_block_data commands
+  I2C_FUNC_SMBUS_I2C_BLOCK        Handles the SMBus read_i2c_block_data
+                                  and write_i2c_block_data commands
+  I2C_FUNC_SMBUS_EMUL             Handles all SMBus commands that can be
+                                  emulated by a real I2C adapter (using
+                                  the transparent emulation layer)
+  =========================       ======================================
+
+In kernel versions prior to 3.5 I2C_FUNC_NOSTART was implemented as
+part of I2C_FUNC_PROTOCOL_MANGLING.
+
+
+ADAPTER IMPLEMENTATION
+----------------------
+
+When you write a new adapter driver, you will have to implement a
+function callback ``functionality``. Typical implementations are given
+below.
+
+A typical SMBus-only adapter would list all the SMBus transactions it
+supports. This example comes from the i2c-piix4 driver::
+
+  static u32 piix4_func(struct i2c_adapter *adapter)
+  {
+	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
+	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
+	       I2C_FUNC_SMBUS_BLOCK_DATA;
+  }
+
+A typical full-I2C adapter would use the following (from the i2c-pxa
+driver)::
+
+  static u32 i2c_pxa_functionality(struct i2c_adapter *adap)
+  {
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+  }
+
+I2C_FUNC_SMBUS_EMUL includes all the SMBus transactions (with the
+addition of I2C block transactions) which i2c-core can emulate using
+I2C_FUNC_I2C without any help from the adapter driver. The idea is
+to let the client drivers check for the support of SMBus functions
+without having to care whether the said functions are implemented in
+hardware by the adapter, or emulated in software by i2c-core on top
+of an I2C adapter.
+
+
+CLIENT CHECKING
+---------------
+
+Before a client tries to attach to an adapter, or even do tests to check
+whether one of the devices it supports is present on an adapter, it should
+check whether the needed functionality is present. The typical way to do
+this is (from the lm75 driver)::
+
+  static int lm75_detect(...)
+  {
+	(...)
+	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
+				     I2C_FUNC_SMBUS_WORD_DATA))
+		goto exit;
+	(...)
+  }
+
+Here, the lm75 driver checks if the adapter can do both SMBus byte data
+and SMBus word data transactions. If not, then the driver won't work on
+this adapter and there's no point in going on. If the check above is
+successful, then the driver knows that it can call the following
+functions: i2c_smbus_read_byte_data(), i2c_smbus_write_byte_data(),
+i2c_smbus_read_word_data() and i2c_smbus_write_word_data(). As a rule of
+thumb, the functionality constants you test for with
+i2c_check_functionality() should match exactly the i2c_smbus_* functions
+which you driver is calling.
+
+Note that the check above doesn't tell whether the functionalities are
+implemented in hardware by the underlying adapter or emulated in
+software by i2c-core. Client drivers don't have to care about this, as
+i2c-core will transparently implement SMBus transactions on top of I2C
+adapters.
+
+
+CHECKING THROUGH /DEV
+---------------------
+
+If you try to access an adapter from a userspace program, you will have
+to use the /dev interface. You will still have to check whether the
+functionality you need is supported, of course. This is done using
+the I2C_FUNCS ioctl. An example, adapted from the i2cdetect program, is
+below::
+
+  int file;
+  if (file = open("/dev/i2c-0", O_RDWR) < 0) {
+	/* Some kind of error handling */
+	exit(1);
+  }
+  if (ioctl(file, I2C_FUNCS, &funcs) < 0) {
+	/* Some kind of error handling */
+	exit(1);
+  }
+  if (!(funcs & I2C_FUNC_SMBUS_QUICK)) {
+	/* Oops, the needed functionality (SMBus write_quick function) is
+           not available! */
+	exit(1);
+  }
+  /* Now it is safe to use the SMBus write_quick command */