Merge tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-coregrafted

Pull driver core fixes from Danilo Krummrich:

 - Fix kernfs listxattr() not returning security xattr names (e.g.
   SELinux labels) when the kernfs node has no allocated kernfs_iattrs

 - Fix silent truncation of IRQ vector indices in the Rust PCI
   abstractions

 - Don't select OF from DRIVER_PE_KUNIT_TEST; skip the test when OF is
   disabled instead of silently enabling extra kernel functionality

 - Russ Weight is retiring from kernel development; update the Firmware
   Loader sysfs contact to the driver-core mailing list, add a CREDITS
   entry for Firmware Upload, and update MAINTAINERS accordingly

* tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core:
  MAINTAINERS: Remove Russ Weight from Firmware Loader
  CREDITS: Add CREDITS entry for Firmware Upload
  firmware_loader: Change contact for sysfs nodes
  rust: pci: reject IRQ vector indices that do not fit in u32
  kernfs: preserve security xattrs without allocating iattrs
  drivers: base: test: DRIVER_PE_KUNIT_TEST should not select OF

1 files changed, 88 insertions, 0 deletions

diff --git a/Documentation/driver-api/hsi.rst b/Documentation/driver-api/hsi.rst
new file mode 100644
index 000000000..01b6bebfb
--- /dev/null
+++ b/Documentation/driver-api/hsi.rst
@@ -0,0 +1,88 @@
+High Speed Synchronous Serial Interface (HSI)
+=============================================
+
+Introduction
+---------------
+
+High Speed Synchronous Interface (HSI) is a full duplex, low latency protocol,
+that is optimized for die-level interconnect between an Application Processor
+and a Baseband chipset. It has been specified by the MIPI alliance in 2003 and
+implemented by multiple vendors since then.
+
+The HSI interface supports full duplex communication over multiple channels
+(typically 8) and is capable of reaching speeds up to 200 Mbit/s.
+
+The serial protocol uses two signals, DATA and FLAG as combined data and clock
+signals and an additional READY signal for flow control. An additional WAKE
+signal can be used to wakeup the chips from standby modes. The signals are
+commonly prefixed by AC for signals going from the application die to the
+cellular die and CA for signals going the other way around.
+
+::
+
+    +------------+                                 +---------------+
+    |  Cellular  |                                 |  Application  |
+    |    Die     |                                 |      Die      |
+    |            | - - - - - - CAWAKE - - - - - - >|               |
+    |           T|------------ CADATA ------------>|R              |
+    |           X|------------ CAFLAG ------------>|X              |
+    |            |<----------- ACREADY ------------|               |
+    |            |                                 |               |
+    |            |                                 |               |
+    |            |< - - - - -  ACWAKE - - - - - - -|               |
+    |           R|<----------- ACDATA -------------|T              |
+    |           X|<----------- ACFLAG -------------|X              |
+    |            |------------ CAREADY ----------->|               |
+    |            |                                 |               |
+    |            |                                 |               |
+    +------------+                                 +---------------+
+
+HSI Subsystem in Linux
+-------------------------
+
+In the Linux kernel the hsi subsystem is supposed to be used for HSI devices.
+The hsi subsystem contains drivers for hsi controllers including support for
+multi-port controllers and provides a generic API for using the HSI ports.
+
+It also contains HSI client drivers, which make use of the generic API to
+implement a protocol used on the HSI interface. These client drivers can
+use an arbitrary number of channels.
+
+hsi-char Device
+------------------
+
+Each port automatically registers a generic client driver called hsi_char,
+which provides a character device for userspace representing the HSI port.
+It can be used to communicate via HSI from userspace. Userspace may
+configure the hsi_char device using the following ioctl commands:
+
+HSC_RESET
+ flush the HSI port
+
+HSC_SET_PM
+ enable or disable the client.
+
+HSC_SEND_BREAK
+ send break
+
+HSC_SET_RX
+ set RX configuration
+
+HSC_GET_RX
+ get RX configuration
+
+HSC_SET_TX
+ set TX configuration
+
+HSC_GET_TX
+ get TX configuration
+
+The kernel HSI API
+------------------
+
+.. kernel-doc:: include/linux/hsi/hsi.h
+   :internal:
+
+.. kernel-doc:: drivers/hsi/hsi_core.c
+   :export:
+