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, 109 insertions, 0 deletions

diff --git a/Documentation/admin-guide/media/raspberrypi-pisp-be.rst b/Documentation/admin-guide/media/raspberrypi-pisp-be.rst
new file mode 100644
index 000000000..0fcf46f26
--- /dev/null
+++ b/Documentation/admin-guide/media/raspberrypi-pisp-be.rst
@@ -0,0 +1,109 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================================
+Raspberry Pi PiSP Back End Memory-to-Memory ISP (pisp-be)
+=========================================================
+
+The PiSP Back End
+=================
+
+The PiSP Back End is a memory-to-memory Image Signal Processor (ISP) which reads
+image data from DRAM memory and performs image processing as specified by the
+application through the parameters in a configuration buffer, before writing
+pixel data back to memory through two distinct output channels.
+
+The ISP registers and programming model are documented in the `Raspberry Pi
+Image Signal Processor (PiSP) Specification document`_
+
+The PiSP Back End ISP processes images in tiles. The handling of image
+tessellation and the computation of low-level configuration parameters is
+realized by a free software library called `libpisp
+<https://github.com/raspberrypi/libpisp>`_.
+
+The full image processing pipeline, which involves capturing RAW Bayer data from
+an image sensor through a MIPI CSI-2 compatible capture interface, storing them
+in DRAM memory and processing them in the PiSP Back End to obtain images usable
+by an application is implemented in `libcamera <https://libcamera.org>`_ as
+part of the Raspberry Pi platform support.
+
+The pisp-be driver
+==================
+
+The Raspberry Pi PiSP Back End (pisp-be) driver is located under
+drivers/media/platform/raspberrypi/pisp-be. It uses the `V4L2 API` to register
+a number of video capture and output devices, the `V4L2 subdev API` to register
+a subdevice for the ISP that connects the video devices in a single media graph
+realized using the `Media Controller (MC) API`.
+
+The media topology registered by the `pisp-be` driver is represented below:
+
+.. _pips-be-topology:
+
+.. kernel-figure:: raspberrypi-pisp-be.dot
+    :alt:   Diagram of the default media pipeline topology
+    :align: center
+
+
+The media graph registers the following video device nodes:
+
+- pispbe-input: output device for images to be submitted to the ISP for
+  processing.
+- pispbe-tdn_input: output device for temporal denoise.
+- pispbe-stitch_input: output device for image stitching (HDR).
+- pispbe-output0: first capture device for processed images.
+- pispbe-output1: second capture device for processed images.
+- pispbe-tdn_output: capture device for temporal denoise.
+- pispbe-stitch_output: capture device for image stitching (HDR).
+- pispbe-config: output device for ISP configuration parameters.
+
+pispbe-input
+------------
+
+Images to be processed by the ISP are queued to the `pispbe-input` output device
+node. For a list of image formats supported as input to the ISP refer to the
+`Raspberry Pi Image Signal Processor (PiSP) Specification document`_.
+
+pispbe-tdn_input, pispbe-tdn_output
+-----------------------------------
+
+The `pispbe-tdn_input` output video device receives images to be processed by
+the temporal denoise block which are captured from the `pispbe-tdn_output`
+capture video device. Userspace is responsible for maintaining queues on both
+devices, and ensuring that buffers completed on the output are queued to the
+input.
+
+pispbe-stitch_input, pispbe-stitch_output
+-----------------------------------------
+
+To realize HDR (high dynamic range) image processing the image stitching and
+tonemapping blocks are used. The `pispbe-stitch_output` writes images to memory
+and the `pispbe-stitch_input` receives the previously written frame to process
+it along with the current input image. Userspace is responsible for maintaining
+queues on both devices, and ensuring that buffers completed on the output are
+queued to the input.
+
+pispbe-output0, pispbe-output1
+------------------------------
+
+The two capture devices write to memory the pixel data as processed by the ISP.
+
+pispbe-config
+-------------
+
+The `pispbe-config` output video devices receives a buffer of configuration
+parameters that define the desired image processing to be performed by the ISP.
+
+The format of the ISP configuration parameter is defined by
+:c:type:`pisp_be_tiles_config` C structure and the meaning of each parameter is
+described in the `Raspberry Pi Image Signal Processor (PiSP) Specification
+document`_.
+
+ISP configuration
+=================
+
+The ISP configuration is described solely by the content of the parameters
+buffer. The only parameter that userspace needs to configure using the V4L2 API
+is the image format on the output and capture video devices for validation of
+the content of the parameters buffer.
+
+.. _Raspberry Pi Image Signal Processor (PiSP) Specification document: https://datasheets.raspberrypi.com/camera/raspberry-pi-image-signal-processor-specification.pdf