Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

1 files changed, 132 insertions, 0 deletions

diff --git a/Documentation/networking/nfc.rst b/Documentation/networking/nfc.rst
new file mode 100644
index 000000000..401735006
--- /dev/null
+++ b/Documentation/networking/nfc.rst
@@ -0,0 +1,132 @@
+===================
+Linux NFC subsystem
+===================
+
+The Near Field Communication (NFC) subsystem is required to standardize the
+NFC device drivers development and to create an unified userspace interface.
+
+This document covers the architecture overview, the device driver interface
+description and the userspace interface description.
+
+Architecture overview
+=====================
+
+The NFC subsystem is responsible for:
+      - NFC adapters management;
+      - Polling for targets;
+      - Low-level data exchange;
+
+The subsystem is divided in some parts. The 'core' is responsible for
+providing the device driver interface. On the other side, it is also
+responsible for providing an interface to control operations and low-level
+data exchange.
+
+The control operations are available to userspace via generic netlink.
+
+The low-level data exchange interface is provided by the new socket family
+PF_NFC. The NFC_SOCKPROTO_RAW performs raw communication with NFC targets.
+
+.. code-block:: none
+
+        +--------------------------------------+
+        |              USER SPACE              |
+        +--------------------------------------+
+            ^                       ^
+            | low-level             | control
+            | data exchange         | operations
+            |                       |
+            |                       v
+            |                  +-----------+
+            | AF_NFC           |  netlink  |
+            | socket           +-----------+
+            | raw                   ^
+            |                       |
+            v                       v
+        +---------+            +-----------+
+        | rawsock | <--------> |   core    |
+        +---------+            +-----------+
+                                    ^
+                                    |
+                                    v
+                               +-----------+
+                               |  driver   |
+                               +-----------+
+
+Device Driver Interface
+=======================
+
+When registering on the NFC subsystem, the device driver must inform the core
+of the set of supported NFC protocols and the set of ops callbacks. The ops
+callbacks that must be implemented are the following:
+
+* start_poll - setup the device to poll for targets
+* stop_poll - stop on progress polling operation
+* activate_target - select and initialize one of the targets found
+* deactivate_target - deselect and deinitialize the selected target
+* data_exchange - send data and receive the response (transceive operation)
+
+Userspace interface
+===================
+
+The userspace interface is divided in control operations and low-level data
+exchange operation.
+
+Control operations
+------------------
+
+Generic netlink is used to implement the interface to the control operations.
+The operations are composed by commands and events, all listed below:
+
+* NFC_CMD_GET_DEVICE - get specific device info or dump the device list
+* NFC_CMD_START_POLL - setup a specific device to polling for targets
+* NFC_CMD_STOP_POLL - stop the polling operation in a specific device
+* NFC_CMD_GET_TARGET - dump the list of targets found by a specific device
+
+* NFC_EVENT_DEVICE_ADDED - reports an NFC device addition
+* NFC_EVENT_DEVICE_REMOVED - reports an NFC device removal
+* NFC_EVENT_TARGETS_FOUND - reports START_POLL results when 1 or more targets
+  are found
+
+The user must call START_POLL to poll for NFC targets, passing the desired NFC
+protocols through NFC_ATTR_PROTOCOLS attribute. The device remains in polling
+state until it finds any target. However, the user can stop the polling
+operation by calling STOP_POLL command. In this case, it will be checked if
+the requester of STOP_POLL is the same of START_POLL.
+
+If the polling operation finds one or more targets, the event TARGETS_FOUND is
+sent (including the device id). The user must call GET_TARGET to get the list of
+all targets found by such device. Each reply message has target attributes with
+relevant information such as the supported NFC protocols.
+
+All polling operations requested through one netlink socket are stopped when
+it's closed.
+
+Low-level data exchange
+-----------------------
+
+The userspace must use PF_NFC sockets to perform any data communication with
+targets. All NFC sockets use AF_NFC::
+
+        struct sockaddr_nfc {
+               sa_family_t sa_family;
+               __u32 dev_idx;
+               __u32 target_idx;
+               __u32 nfc_protocol;
+        };
+
+To establish a connection with one target, the user must create an
+NFC_SOCKPROTO_RAW socket and call the 'connect' syscall with the sockaddr_nfc
+struct correctly filled. All information comes from NFC_EVENT_TARGETS_FOUND
+netlink event. As a target can support more than one NFC protocol, the user
+must inform which protocol it wants to use.
+
+Internally, 'connect' will result in an activate_target call to the driver.
+When the socket is closed, the target is deactivated.
+
+The data format exchanged through the sockets is NFC protocol dependent. For
+instance, when communicating with MIFARE tags, the data exchanged are MIFARE
+commands and their responses.
+
+The first received package is the response to the first sent package and so
+on. In order to allow valid "empty" responses, every data received has a NULL
+header of 1 byte.