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, 136 insertions, 0 deletions

diff --git a/Documentation/misc-devices/max6875.rst b/Documentation/misc-devices/max6875.rst
new file mode 100644
index 000000000..ad419ac22
--- /dev/null
+++ b/Documentation/misc-devices/max6875.rst
@@ -0,0 +1,136 @@
+=====================
+Kernel driver max6875
+=====================
+
+Supported chips:
+
+  * Maxim MAX6874, MAX6875
+
+    Prefix: 'max6875'
+
+    Addresses scanned: None (see below)
+
+    Datasheet: http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf
+
+Author: Ben Gardner <bgardner@wabtec.com>
+
+
+Description
+-----------
+
+The Maxim MAX6875 is an EEPROM-programmable power-supply sequencer/supervisor.
+It provides timed outputs that can be used as a watchdog, if properly wired.
+It also provides 512 bytes of user EEPROM.
+
+At reset, the MAX6875 reads the configuration EEPROM into its configuration
+registers.  The chip then begins to operate according to the values in the
+registers.
+
+The Maxim MAX6874 is a similar, mostly compatible device, with more inputs
+and outputs:
+
+===========  ===     ===    ====
+-            vin     gpi    vout
+===========  ===     ===    ====
+MAX6874        6       4       8
+MAX6875        4       3       5
+===========  ===     ===    ====
+
+See the datasheet for more information.
+
+
+Sysfs entries
+-------------
+
+eeprom        - 512 bytes of user-defined EEPROM space.
+
+
+General Remarks
+---------------
+
+Valid addresses for the MAX6875 are 0x50 and 0x52.
+
+Valid addresses for the MAX6874 are 0x50, 0x52, 0x54 and 0x56.
+
+The driver does not probe any address, so you explicitly instantiate the
+devices.
+
+Example::
+
+  $ modprobe max6875
+  $ echo max6875 0x50 > /sys/bus/i2c/devices/i2c-0/new_device
+
+The MAX6874/MAX6875 ignores address bit 0, so this driver attaches to multiple
+addresses.  For example, for address 0x50, it also reserves 0x51.
+The even-address instance is called 'max6875', the odd one is 'dummy'.
+
+
+Programming the chip using i2c-dev
+----------------------------------
+
+Use the i2c-dev interface to access and program the chips.
+
+Reads and writes are performed differently depending on the address range.
+
+The configuration registers are at addresses 0x00 - 0x45.
+
+Use i2c_smbus_write_byte_data() to write a register and
+i2c_smbus_read_byte_data() to read a register.
+
+The command is the register number.
+
+Examples:
+
+To write a 1 to register 0x45::
+
+  i2c_smbus_write_byte_data(fd, 0x45, 1);
+
+To read register 0x45::
+
+  value = i2c_smbus_read_byte_data(fd, 0x45);
+
+
+The configuration EEPROM is at addresses 0x8000 - 0x8045.
+
+The user EEPROM is at addresses 0x8100 - 0x82ff.
+
+Use i2c_smbus_write_word_data() to write a byte to EEPROM.
+
+The command is the upper byte of the address: 0x80, 0x81, or 0x82.
+The data word is the lower part of the address or'd with data << 8::
+
+  cmd = address >> 8;
+  val = (address & 0xff) | (data << 8);
+
+Example:
+
+To write 0x5a to address 0x8003::
+
+  i2c_smbus_write_word_data(fd, 0x80, 0x5a03);
+
+
+Reading data from the EEPROM is a little more complicated.
+
+Use i2c_smbus_write_byte_data() to set the read address and then
+i2c_smbus_read_byte() or i2c_smbus_read_i2c_block_data() to read the data.
+
+Example:
+
+To read data starting at offset 0x8100, first set the address::
+
+  i2c_smbus_write_byte_data(fd, 0x81, 0x00);
+
+And then read the data::
+
+  value = i2c_smbus_read_byte(fd);
+
+or::
+
+  count = i2c_smbus_read_i2c_block_data(fd, 0x84, 16, buffer);
+
+The block read should read 16 bytes.
+
+0x84 is the block read command.
+
+See the datasheet for more details.
+