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mei: docs: move documentation under driver-api

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Move mei driver documentation under Documentation/driver-api/
Perform some minimal formating changes to produce correct sphinx rendering
and add index.rst

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tomas Winkler
2019-06-03 12:14:00 +03:00
committed by Greg Kroah-Hartman
parent 381e9760ee
commit 7e527e11d6
5 changed files with 104 additions and 86 deletions
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141
Documentation/misc-devices/mei/mei-client-bus.txt
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Intel(R) Management Engine (ME) Client bus API
==============================================
Rationale
=========
MEI misc character device is useful for dedicated applications to send and receive
data to the many FW appliance found in Intel's ME from the user space.
However for some of the ME functionalities it make sense to leverage existing software
stack and expose them through existing kernel subsystems.
In order to plug seamlessly into the kernel device driver model we add kernel virtual
bus abstraction on top of the MEI driver. This allows implementing linux kernel drivers
for the various MEI features as a stand alone entities found in their respective subsystem.
Existing device drivers can even potentially be re-used by adding an MEI CL bus layer to
the existing code.
MEI CL bus API
==============
A driver implementation for an MEI Client is very similar to existing bus
based device drivers. The driver registers itself as an MEI CL bus driver through
the mei_cl_driver structure:
struct mei_cl_driver {
struct device_driver driver;
const char *name;
const struct mei_cl_device_id *id_table;
int (*probe)(struct mei_cl_device *dev, const struct mei_cl_id *id);
int (*remove)(struct mei_cl_device *dev);
};
struct mei_cl_id {
char name[MEI_NAME_SIZE];
kernel_ulong_t driver_info;
};
The mei_cl_id structure allows the driver to bind itself against a device name.
To actually register a driver on the ME Client bus one must call the mei_cl_add_driver()
API. This is typically called at module init time.
Once registered on the ME Client bus, a driver will typically try to do some I/O on
this bus and this should be done through the mei_cl_send() and mei_cl_recv()
routines. The latter is synchronous (blocks and sleeps until data shows up).
In order for drivers to be notified of pending events waiting for them (e.g.
an Rx event) they can register an event handler through the
mei_cl_register_event_cb() routine. Currently only the MEI_EVENT_RX event
will trigger an event handler call and the driver implementation is supposed
to call mei_recv() from the event handler in order to fetch the pending
received buffers.
Example
=======
As a theoretical example let's pretend the ME comes with a "contact" NFC IP.
The driver init and exit routines for this device would look like:
#define CONTACT_DRIVER_NAME "contact"
static struct mei_cl_device_id contact_mei_cl_tbl[] = {
{ CONTACT_DRIVER_NAME, },
/* required last entry */
{ }
};
MODULE_DEVICE_TABLE(mei_cl, contact_mei_cl_tbl);
static struct mei_cl_driver contact_driver = {
.id_table = contact_mei_tbl,
.name = CONTACT_DRIVER_NAME,
.probe = contact_probe,
.remove = contact_remove,
};
static int contact_init(void)
{
int r;
r = mei_cl_driver_register(&contact_driver);
if (r) {
pr_err(CONTACT_DRIVER_NAME ": driver registration failed\n");
return r;
}
return 0;
}
static void __exit contact_exit(void)
{
mei_cl_driver_unregister(&contact_driver);
}
module_init(contact_init);
module_exit(contact_exit);
And the driver's simplified probe routine would look like that:
int contact_probe(struct mei_cl_device *dev, struct mei_cl_device_id *id)
{
struct contact_driver *contact;
[...]
mei_cl_enable_device(dev);
mei_cl_register_event_cb(dev, contact_event_cb, contact);
return 0;
}
In the probe routine the driver first enable the MEI device and then registers
an ME bus event handler which is as close as it can get to registering a
threaded IRQ handler.
The handler implementation will typically call some I/O routine depending on
the pending events:
#define MAX_NFC_PAYLOAD 128
static void contact_event_cb(struct mei_cl_device *dev, u32 events,
void *context)
{
struct contact_driver *contact = context;
if (events & BIT(MEI_EVENT_RX)) {
u8 payload[MAX_NFC_PAYLOAD];
int payload_size;
payload_size = mei_recv(dev, payload, MAX_NFC_PAYLOAD);
if (payload_size <= 0)
return;
/* Hook to the NFC subsystem */
nfc_hci_recv_frame(contact->hdev, payload, payload_size);
}
}

266
Documentation/misc-devices/mei/mei.txt
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Intel(R) Management Engine Interface (Intel(R) MEI)
===================================================
Introduction
============
The Intel Management Engine (Intel ME) is an isolated and protected computing
resource (Co-processor) residing inside certain Intel chipsets. The Intel ME
provides support for computer/IT management features. The feature set
depends on the Intel chipset SKU.
The Intel Management Engine Interface (Intel MEI, previously known as HECI)
is the interface between the Host and Intel ME. This interface is exposed
to the host as a PCI device. The Intel MEI Driver is in charge of the
communication channel between a host application and the Intel ME feature.
Each Intel ME feature (Intel ME Client) is addressed by a GUID/UUID and
each client has its own protocol. The protocol is message-based with a
header and payload up to 512 bytes.
Prominent usage of the Intel ME Interface is to communicate with Intel(R)
Active Management Technology (Intel AMT) implemented in firmware running on
the Intel ME.
Intel AMT provides the ability to manage a host remotely out-of-band (OOB)
even when the operating system running on the host processor has crashed or
is in a sleep state.
Some examples of Intel AMT usage are:
- Monitoring hardware state and platform components
- Remote power off/on (useful for green computing or overnight IT
maintenance)
- OS updates
- Storage of useful platform information such as software assets
- Built-in hardware KVM
- Selective network isolation of Ethernet and IP protocol flows based
on policies set by a remote management console
- IDE device redirection from remote management console
Intel AMT (OOB) communication is based on SOAP (deprecated
starting with Release 6.0) over HTTP/S or WS-Management protocol over
HTTP/S that are received from a remote management console application.
For more information about Intel AMT:
http://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide
Intel MEI Driver
================
The driver exposes a misc device called /dev/mei.
An application maintains communication with an Intel ME feature while
/dev/mei is open. The binding to a specific feature is performed by calling
MEI_CONNECT_CLIENT_IOCTL, which passes the desired UUID.
The number of instances of an Intel ME feature that can be opened
at the same time depends on the Intel ME feature, but most of the
features allow only a single instance.
The Intel AMT Host Interface (Intel AMTHI) feature supports multiple
simultaneous user connected applications. The Intel MEI driver
handles this internally by maintaining request queues for the applications.
The driver is transparent to data that are passed between firmware feature
and host application.
Because some of the Intel ME features can change the system
configuration, the driver by default allows only a privileged
user to access it.
A code snippet for an application communicating with Intel AMTHI client:
struct mei_connect_client_data data;
fd = open(MEI_DEVICE);
data.d.in_client_uuid = AMTHI_UUID;
ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &data);
printf("Ver=%d, MaxLen=%ld\n",
data.d.in_client_uuid.protocol_version,
data.d.in_client_uuid.max_msg_length);
[...]
write(fd, amthi_req_data, amthi_req_data_len);
[...]
read(fd, &amthi_res_data, amthi_res_data_len);
[...]
close(fd);
IOCTL
=====
The Intel MEI Driver supports the following IOCTL commands:
IOCTL_MEI_CONNECT_CLIENT Connect to firmware Feature (client).
usage:
struct mei_connect_client_data clientData;
ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &clientData);
inputs:
mei_connect_client_data struct contain the following
input field:
in_client_uuid - UUID of the FW Feature that needs
to connect to.
outputs:
out_client_properties - Client Properties: MTU and Protocol Version.
error returns:
EINVAL Wrong IOCTL Number
ENODEV Device or Connection is not initialized or ready.
(e.g. Wrong UUID)
ENOMEM Unable to allocate memory to client internal data.
EFAULT Fatal Error (e.g. Unable to access user input data)
EBUSY Connection Already Open
Notes:
max_msg_length (MTU) in client properties describes the maximum
data that can be sent or received. (e.g. if MTU=2K, can send
requests up to bytes 2k and received responses up to 2k bytes).
IOCTL_MEI_NOTIFY_SET: enable or disable event notifications
Usage:
uint32_t enable;
ioctl(fd, IOCTL_MEI_NOTIFY_SET, &enable);
Inputs:
uint32_t enable = 1;
or
uint32_t enable[disable] = 0;
Error returns:
EINVAL Wrong IOCTL Number
ENODEV Device is not initialized or the client not connected
ENOMEM Unable to allocate memory to client internal data.
EFAULT Fatal Error (e.g. Unable to access user input data)
EOPNOTSUPP if the device doesn't support the feature
Notes:
The client must be connected in order to enable notification events
IOCTL_MEI_NOTIFY_GET : retrieve event
Usage:
uint32_t event;
ioctl(fd, IOCTL_MEI_NOTIFY_GET, &event);
Outputs:
1 - if an event is pending
0 - if there is no even pending
Error returns:
EINVAL Wrong IOCTL Number
ENODEV Device is not initialized or the client not connected
ENOMEM Unable to allocate memory to client internal data.
EFAULT Fatal Error (e.g. Unable to access user input data)
EOPNOTSUPP if the device doesn't support the feature
Notes:
The client must be connected and event notification has to be enabled
in order to receive an event
Intel ME Applications
=====================
1) Intel Local Management Service (Intel LMS)
Applications running locally on the platform communicate with Intel AMT Release
2.0 and later releases in the same way that network applications do via SOAP
over HTTP (deprecated starting with Release 6.0) or with WS-Management over
SOAP over HTTP. This means that some Intel AMT features can be accessed from a
local application using the same network interface as a remote application
communicating with Intel AMT over the network.
When a local application sends a message addressed to the local Intel AMT host
name, the Intel LMS, which listens for traffic directed to the host name,
intercepts the message and routes it to the Intel MEI.
For more information:
http://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide
Under "About Intel AMT" => "Local Access"
For downloading Intel LMS:
http://software.intel.com/en-us/articles/download-the-latest-intel-amt-open-source-drivers/
The Intel LMS opens a connection using the Intel MEI driver to the Intel LMS
firmware feature using a defined UUID and then communicates with the feature
using a protocol called Intel AMT Port Forwarding Protocol (Intel APF protocol).
The protocol is used to maintain multiple sessions with Intel AMT from a
single application.
See the protocol specification in the Intel AMT Software Development Kit (SDK)
http://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide
Under "SDK Resources" => "Intel(R) vPro(TM) Gateway (MPS)"
=> "Information for Intel(R) vPro(TM) Gateway Developers"
=> "Description of the Intel AMT Port Forwarding (APF) Protocol"
2) Intel AMT Remote configuration using a Local Agent
A Local Agent enables IT personnel to configure Intel AMT out-of-the-box
without requiring installing additional data to enable setup. The remote
configuration process may involve an ISV-developed remote configuration
agent that runs on the host.
For more information:
http://software.intel.com/sites/manageability/AMT_Implementation_and_Reference_Guide
Under "Setup and Configuration of Intel AMT" =>
"SDK Tools Supporting Setup and Configuration" =>
"Using the Local Agent Sample"
An open source Intel AMT configuration utility, implementing a local agent
that accesses the Intel MEI driver, can be found here:
http://software.intel.com/en-us/articles/download-the-latest-intel-amt-open-source-drivers/
Intel AMT OS Health Watchdog
============================
The Intel AMT Watchdog is an OS Health (Hang/Crash) watchdog.
Whenever the OS hangs or crashes, Intel AMT will send an event
to any subscriber to this event. This mechanism means that
IT knows when a platform crashes even when there is a hard failure on the host.
The Intel AMT Watchdog is composed of two parts:
1) Firmware feature - receives the heartbeats
and sends an event when the heartbeats stop.
2) Intel MEI iAMT watchdog driver - connects to the watchdog feature,
configures the watchdog and sends the heartbeats.
The Intel iAMT watchdog MEI driver uses the kernel watchdog API to configure
the Intel AMT Watchdog and to send heartbeats to it. The default timeout of the
watchdog is 120 seconds.
If the Intel AMT is not enabled in the firmware then the watchdog client won't enumerate
on the me client bus and watchdog devices won't be exposed.
Supported Chipsets
==================
7 Series Chipset Family
6 Series Chipset Family
5 Series Chipset Family
4 Series Chipset Family
Mobile 4 Series Chipset Family
ICH9
82946GZ/GL
82G35 Express
82Q963/Q965
82P965/G965
Mobile PM965/GM965
Mobile GME965/GLE960
82Q35 Express
82G33/G31/P35/P31 Express
82Q33 Express
82X38/X48 Express
---
linux-mei@linux.intel.com