Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 204 insertions, 0 deletions

diff --git a/Documentation/driver-api/surface_aggregator/clients/cdev.rst b/Documentation/driver-api/surface_aggregator/clients/cdev.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+.. |ssam_cdev_request| replace:: :c:type:`struct ssam_cdev_request <ssam_cdev_request>`
+.. |ssam_cdev_request_flags| replace:: :c:type:`enum ssam_cdev_request_flags <ssam_cdev_request_flags>`
+.. |ssam_cdev_event| replace:: :c:type:`struct ssam_cdev_event <ssam_cdev_event>`
+
+==============================
+User-Space EC Interface (cdev)
+==============================
+
+The ``surface_aggregator_cdev`` module provides a misc-device for the SSAM
+controller to allow for a (more or less) direct connection from user-space to
+the SAM EC. It is intended to be used for development and debugging, and
+therefore should not be used or relied upon in any other way. Note that this
+module is not loaded automatically, but instead must be loaded manually.
+
+The provided interface is accessible through the ``/dev/surface/aggregator``
+device-file. All functionality of this interface is provided via IOCTLs.
+These IOCTLs and their respective input/output parameter structs are defined in
+``include/uapi/linux/surface_aggregator/cdev.h``.
+
+A small python library and scripts for accessing this interface can be found
+at https://github.com/linux-surface/surface-aggregator-module/tree/master/scripts/ssam.
+
+.. contents::
+
+
+Receiving Events
+================
+
+Events can be received by reading from the device-file. The are represented by
+the |ssam_cdev_event| datatype.
+
+Before events are available to be read, however, the desired notifiers must be
+registered via the ``SSAM_CDEV_NOTIF_REGISTER`` IOCTL. Notifiers are, in
+essence, callbacks, called when the EC sends an event. They are, in this
+interface, associated with a specific target category and device-file-instance.
+They forward any event of this category to the buffer of the corresponding
+instance, from which it can then be read.
+
+Notifiers themselves do not enable events on the EC. Thus, it may additionally
+be necessary to enable events via the ``SSAM_CDEV_EVENT_ENABLE`` IOCTL. While
+notifiers work per-client (i.e. per-device-file-instance), events are enabled
+globally, for the EC and all of its clients (regardless of userspace or
+non-userspace). The ``SSAM_CDEV_EVENT_ENABLE`` and ``SSAM_CDEV_EVENT_DISABLE``
+IOCTLs take care of reference counting the events, such that an event is
+enabled as long as there is a client that has requested it.
+
+Note that enabled events are not automatically disabled once the client
+instance is closed. Therefore any client process (or group of processes) should
+balance their event enable calls with the corresponding event disable calls. It
+is, however, perfectly valid to enable and disable events on different client
+instances. For example, it is valid to set up notifiers and read events on
+client instance ``A``, enable those events on instance ``B`` (note that these
+will also be received by A since events are enabled/disabled globally), and
+after no more events are desired, disable the previously enabled events via
+instance ``C``.
+
+
+Controller IOCTLs
+=================
+
+The following IOCTLs are provided:
+
+.. flat-table:: Controller IOCTLs
+   :widths: 1 1 1 1 4
+   :header-rows: 1
+
+   * - Type
+     - Number
+     - Direction
+     - Name
+     - Description
+
+   * - ``0xA5``
+     - ``1``
+     - ``WR``
+     - ``REQUEST``
+     - Perform synchronous SAM request.
+
+   * - ``0xA5``
+     - ``2``
+     - ``W``
+     - ``NOTIF_REGISTER``
+     - Register event notifier.
+
+   * - ``0xA5``
+     - ``3``
+     - ``W``
+     - ``NOTIF_UNREGISTER``
+     - Unregister event notifier.
+
+   * - ``0xA5``
+     - ``4``
+     - ``W``
+     - ``EVENT_ENABLE``
+     - Enable event source.
+
+   * - ``0xA5``
+     - ``5``
+     - ``W``
+     - ``EVENT_DISABLE``
+     - Disable event source.
+
+
+``SSAM_CDEV_REQUEST``
+---------------------
+
+Defined as ``_IOWR(0xA5, 1, struct ssam_cdev_request)``.
+
+Executes a synchronous SAM request. The request specification is passed in
+as argument of type |ssam_cdev_request|, which is then written to/modified
+by the IOCTL to return status and result of the request.
+
+Request payload data must be allocated separately and is passed in via the
+``payload.data`` and ``payload.length`` members. If a response is required,
+the response buffer must be allocated by the caller and passed in via the
+``response.data`` member. The ``response.length`` member must be set to the
+capacity of this buffer, or if no response is required, zero. Upon
+completion of the request, the call will write the response to the response
+buffer (if its capacity allows it) and overwrite the length field with the
+actual size of the response, in bytes.
+
+Additionally, if the request has a response, this must be indicated via the
+request flags, as is done with in-kernel requests. Request flags can be set
+via the ``flags`` member and the values correspond to the values found in
+|ssam_cdev_request_flags|.
+
+Finally, the status of the request itself is returned in the ``status``
+member (a negative errno value indicating failure). Note that failure
+indication of the IOCTL is separated from failure indication of the request:
+The IOCTL returns a negative status code if anything failed during setup of
+the request (``-EFAULT``) or if the provided argument or any of its fields
+are invalid (``-EINVAL``). In this case, the status value of the request
+argument may be set, providing more detail on what went wrong (e.g.
+``-ENOMEM`` for out-of-memory), but this value may also be zero. The IOCTL
+will return with a zero status code in case the request has been set up,
+submitted, and completed (i.e. handed back to user-space) successfully from
+inside the IOCTL, but the request ``status`` member may still be negative in
+case the actual execution of the request failed after it has been submitted.
+
+A full definition of the argument struct is provided below.
+
+``SSAM_CDEV_NOTIF_REGISTER``
+----------------------------
+
+Defined as ``_IOW(0xA5, 2, struct ssam_cdev_notifier_desc)``.
+
+Register a notifier for the event target category specified in the given
+notifier description with the specified priority. Notifiers registration is
+required to receive events, but does not enable events themselves. After a
+notifier for a specific target category has been registered, all events of that
+category will be forwarded to the userspace client and can then be read from
+the device file instance. Note that events may have to be enabled, e.g. via the
+``SSAM_CDEV_EVENT_ENABLE`` IOCTL, before the EC will send them.
+
+Only one notifier can be registered per target category and client instance. If
+a notifier has already been registered, this IOCTL will fail with ``-EEXIST``.
+
+Notifiers will automatically be removed when the device file instance is
+closed.
+
+``SSAM_CDEV_NOTIF_UNREGISTER``
+------------------------------
+
+Defined as ``_IOW(0xA5, 3, struct ssam_cdev_notifier_desc)``.
+
+Unregisters the notifier associated with the specified target category. The
+priority field will be ignored by this IOCTL. If no notifier has been
+registered for this client instance and the given category, this IOCTL will
+fail with ``-ENOENT``.
+
+``SSAM_CDEV_EVENT_ENABLE``
+--------------------------
+
+Defined as ``_IOW(0xA5, 4, struct ssam_cdev_event_desc)``.
+
+Enable the event associated with the given event descriptor.
+
+Note that this call will not register a notifier itself, it will only enable
+events on the controller. If you want to receive events by reading from the
+device file, you will need to register the corresponding notifier(s) on that
+instance.
+
+Events are not automatically disabled when the device file is closed. This must
+be done manually, via a call to the ``SSAM_CDEV_EVENT_DISABLE`` IOCTL.
+
+``SSAM_CDEV_EVENT_DISABLE``
+---------------------------
+
+Defined as ``_IOW(0xA5, 5, struct ssam_cdev_event_desc)``.
+
+Disable the event associated with the given event descriptor.
+
+Note that this will not unregister any notifiers. Events may still be received
+and forwarded to user-space after this call. The only safe way of stopping
+events from being received is unregistering all previously registered
+notifiers.
+
+
+Structures and Enums
+====================
+
+.. kernel-doc:: include/uapi/linux/surface_aggregator/cdev.h