6 files changed, 79 insertions, 9 deletions

diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
index 20e07e40be02..46c13780994c 100644
--- a/Documentation/driver-api/driver-model/devres.rst
+++ b/Documentation/driver-api/driver-model/devres.rst
@@ -267,6 +267,8 @@ DRM
 
 GPIO
   devm_gpiod_get()
+  devm_gpiod_get_array()
+  devm_gpiod_get_array_optional()
   devm_gpiod_get_index()
   devm_gpiod_get_index_optional()
   devm_gpiod_get_optional()
diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst
index 2ff743105927..871922529332 100644
--- a/Documentation/driver-api/gpio/driver.rst
+++ b/Documentation/driver-api/gpio/driver.rst
@@ -507,11 +507,6 @@ available but we try to move away from this:
   cascaded irq has to be handled by a threaded interrupt handler.
   Apart from that it works exactly like the chained irqchip.
 
-- DEPRECATED: gpiochip_set_chained_irqchip(): sets up a chained cascaded irq
-  handler for a gpio_chip from a parent IRQ and passes the struct gpio_chip*
-  as handler data. Notice that we pass is as the handler data, since the
-  irqchip data is likely used by the parent irqchip.
-
 - gpiochip_set_nested_irqchip(): sets up a nested cascaded irq handler for a
   gpio_chip from a parent IRQ. As the parent IRQ has usually been
   explicitly requested by the driver, this does very little more than
diff --git a/Documentation/driver-api/gpio/drivers-on-gpio.rst b/Documentation/driver-api/gpio/drivers-on-gpio.rst
index f3a189320e11..820b403d50f6 100644
--- a/Documentation/driver-api/gpio/drivers-on-gpio.rst
+++ b/Documentation/driver-api/gpio/drivers-on-gpio.rst
@@ -95,7 +95,7 @@ to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The
 MTD NOR flash has add-ons for extra GPIO lines too, though the address bus is
 usually connected directly to the flash.
 
-Use those instead of talking directly to the GPIOs using sysfs; they integrate
-with kernel frameworks better than your userspace code could. Needless to say,
-just using the appropriate kernel drivers will simplify and speed up your
-embedded hacking in particular by providing ready-made components.
+Use those instead of talking directly to the GPIOs from userspace; they
+integrate with kernel frameworks better than your userspace code could.
+Needless to say, just using the appropriate kernel drivers will simplify and
+speed up your embedded hacking in particular by providing ready-made components.
diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst
index 5b61032aa4ea..1d48fe248f05 100644
--- a/Documentation/driver-api/gpio/index.rst
+++ b/Documentation/driver-api/gpio/index.rst
@@ -8,6 +8,7 @@ Contents:
    :maxdepth: 2
 
    intro
+   using-gpio
    driver
    consumer
    board
diff --git a/Documentation/driver-api/gpio/using-gpio.rst b/Documentation/driver-api/gpio/using-gpio.rst
new file mode 100644
index 000000000000..dda069444032
--- /dev/null
+++ b/Documentation/driver-api/gpio/using-gpio.rst
@@ -0,0 +1,50 @@
+=========================
+Using GPIO Lines in Linux
+=========================
+
+The Linux kernel exists to abstract and present hardware to users. GPIO lines
+as such are normally not user facing abstractions. The most obvious, natural
+and preferred way to use GPIO lines is to let kernel hardware drivers deal
+with them.
+
+For examples of already existing generic drivers that will also be good
+examples for any other kernel drivers you want to author, refer to
+:doc:`drivers-on-gpio`
+
+For any kind of mass produced system you want to support, such as servers,
+laptops, phones, tablets, routers, and any consumer or office or business goods
+using appropriate kernel drivers is paramount. Submit your code for inclusion
+in the upstream Linux kernel when you feel it is mature enough and you will get
+help to refine it, see :doc:`../../process/submitting-patches`.
+
+In Linux GPIO lines also have a userspace ABI.
+
+The userspace ABI is intended for one-off deployments. Examples are prototypes,
+factory lines, maker community projects, workshop specimen, production tools,
+industrial automation, PLC-type use cases, door controllers, in short a piece
+of specialized equipment that is not produced by the numbers, requiring
+operators to have a deep knowledge of the equipment and knows about the
+software-hardware interface to be set up. They should not have a natural fit
+to any existing kernel subsystem and not be a good fit for an operating system,
+because of not being reusable or abstract enough, or involving a lot of non
+computer hardware related policy.
+
+Applications that have a good reason to use the industrial I/O (IIO) subsystem
+from userspace will likely be a good fit for using GPIO lines from userspace as
+well.
+
+Do not under any circumstances abuse the GPIO userspace ABI to cut corners in
+any product development projects. If you use it for prototyping, then do not
+productify the prototype: rewrite it using proper kernel drivers. Do not under
+any circumstances deploy any uniform products using GPIO from userspace.
+
+The userspace ABI is a character device for each GPIO hardware unit (GPIO chip).
+These devices will appear on the system as ``/dev/gpiochip0`` thru
+``/dev/gpiochipN``. Examples of how to directly use the userspace ABI can be
+found in the kernel tree ``tools/gpio`` subdirectory.
+
+For structured and managed applications, we recommend that you make use of the
+libgpiod_ library. This provides helper abstractions, command line utlities
+and arbitration for multiple simultaneous consumers on the same GPIO chip.
+
+.. _libgpiod: https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/
diff --git a/Documentation/driver-api/interconnect.rst b/Documentation/driver-api/interconnect.rst
index cdeb5825f314..5ed4f57a6bac 100644
--- a/Documentation/driver-api/interconnect.rst
+++ b/Documentation/driver-api/interconnect.rst
@@ -91,3 +91,25 @@ Interconnect consumers are the clients which use the interconnect APIs to
 get paths between endpoints and set their bandwidth/latency/QoS requirements
 for these interconnect paths.  These interfaces are not currently
 documented.
+
+Interconnect debugfs interfaces
+-------------------------------
+
+Like several other subsystems interconnect will create some files for debugging
+and introspection. Files in debugfs are not considered ABI so application
+software shouldn't rely on format details change between kernel versions.
+
+``/sys/kernel/debug/interconnect/interconnect_summary``:
+
+Show all interconnect nodes in the system with their aggregated bandwidth
+request. Indented under each node show bandwidth requests from each device.
+
+``/sys/kernel/debug/interconnect/interconnect_graph``:
+
+Show the interconnect graph in the graphviz dot format. It shows all
+interconnect nodes and links in the system and groups together nodes from the
+same provider as subgraphs. The format is human-readable and can also be piped
+through dot to generate diagrams in many graphical formats::
+
+        $ cat /sys/kernel/debug/interconnect/interconnect_graph | \
+                dot -Tsvg > interconnect_graph.svg