Merge tag 'char-misc-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

Pull char/misc driver updates from Greg KH:
 "Here is the big set of char/misc patches for 4.20-rc1.

  Loads of things here, we have new code in all of these driver
  subsystems:
   - fpga
   - stm
   - extcon
   - nvmem
   - eeprom
   - hyper-v
   - gsmi
   - coresight
   - thunderbolt
   - vmw_balloon
   - goldfish
   - soundwire
  along with lots of fixes and minor changes to other small drivers.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'char-misc-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (245 commits)
  Documentation/security-bugs: Clarify treatment of embargoed information
  lib: Fix ia64 bootloader linkage
  MAINTAINERS: Clarify UIO vs UIOVEC maintainer
  docs/uio: fix a grammar nitpick
  docs: fpga: document programming fpgas using regions
  fpga: add devm_fpga_region_create
  fpga: bridge: add devm_fpga_bridge_create
  fpga: mgr: add devm_fpga_mgr_create
  hv_balloon: Replace spin_is_locked() with lockdep
  sgi-xp: Replace spin_is_locked() with lockdep
  eeprom: New ee1004 driver for DDR4 memory
  eeprom: at25: remove unneeded 'at25_remove'
  w1: IAD Register is yet readable trough iad sys file. Fix snprintf (%u for unsigned, count for max size).
  misc: mic: scif: remove set but not used variables 'src_dma_addr, dst_dma_addr'
  misc: mic: fix a DMA pool free failure
  platform: goldfish: pipe: Add a blank line to separate varibles and code
  platform: goldfish: pipe: Remove redundant casting
  platform: goldfish: pipe: Call misc_deregister if init fails
  platform: goldfish: pipe: Move the file-scope goldfish_pipe_dev variable into the driver state
  platform: goldfish: pipe: Move the file-scope goldfish_pipe_miscdev variable into the driver state
  ...

1 files changed, 29 insertions, 9 deletions

diff --git a/Documentation/trace/stm.rst b/Documentation/trace/stm.rst
index 2c22ddb7fd3e..99f99963e5e7 100644
--- a/Documentation/trace/stm.rst
+++ b/Documentation/trace/stm.rst
@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: GPL-2.0
+
 ===================
 System Trace Module
 ===================
@@ -53,12 +55,30 @@ under "user" directory from the example above and this new rule will
 be used for trace sources with the id string of "user/dummy".
 
 Trace sources have to open the stm class device's node and write their
-trace data into its file descriptor. In order to identify themselves
-to the policy, they need to do a STP_POLICY_ID_SET ioctl on this file
-descriptor providing their id string. Otherwise, they will be
-automatically allocated a master/channel pair upon first write to this
-file descriptor according to the "default" rule of the policy, if such
-exists.
+trace data into its file descriptor.
+
+In order to find an appropriate policy node for a given trace source,
+several mechanisms can be used. First, a trace source can explicitly
+identify itself by calling an STP_POLICY_ID_SET ioctl on the character
+device's file descriptor, providing their id string, before they write
+any data there. Secondly, if they chose not to perform the explicit
+identification (because you may not want to patch existing software
+to do this), they can just start writing the data, at which point the
+stm core will try to find a policy node with the name matching the
+task's name (e.g., "syslogd") and if one exists, it will be used.
+Thirdly, if the task name can't be found among the policy nodes, the
+catch-all entry "default" will be used, if it exists. This entry also
+needs to be created and configured by the system administrator or
+whatever tools are taking care of the policy configuration. Finally,
+if all the above steps failed, the write() to an stm file descriptor
+will return a error (EINVAL).
+
+Previously, if no policy nodes were found for a trace source, the stm
+class would silently fall back to allocating the first available
+contiguous range of master/channels from the beginning of the device's
+master/channel range. The new requirement for a policy node to exist
+will help programmers and sysadmins identify gaps in configuration
+and have better control over the un-identified sources.
 
 Some STM devices may allow direct mapping of the channel mmio regions
 to userspace for zero-copy writing. One mappable page (in terms of
@@ -92,9 +112,9 @@ allocated for the device according to the policy configuration. If
 there's a node in the root of the policy directory that matches the
 stm_source device's name (for example, "console"), this node will be
 used to allocate master and channel numbers. If there's no such policy
-node, the stm core will pick the first contiguous chunk of channels
-within the first available master. Note that the node must exist
-before the stm_source device is connected to its stm device.
+node, the stm core will use the catch-all entry "default", if one
+exists. If neither policy nodes exist, the write() to stm_source_link
+will return an error.
 
 stm_console
 ===========