214 lines
5.9 KiB
ReStructuredText
214 lines
5.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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Introduction
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============
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The Intel Management Engine (Intel ME) is an isolated and protected computing
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resource (Co-processor) residing inside certain Intel chipsets. The Intel ME
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provides support for computer/IT management and security features.
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The actual feature set depends on the Intel chipset SKU.
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The Intel Management Engine Interface (Intel MEI, previously known as HECI)
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is the interface between the Host and Intel ME. This interface is exposed
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to the host as a PCI device, actually multiple PCI devices might be exposed.
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The Intel MEI Driver is in charge of the communication channel between
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a host application and the Intel ME features.
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Each Intel ME feature, or Intel ME Client is addressed by a unique GUID and
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each client has its own protocol. The protocol is message-based with a
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header and payload up to maximal number of bytes advertised by the client,
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upon connection.
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Intel MEI Driver
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================
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The driver exposes a character device with device nodes /dev/meiX.
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An application maintains communication with an Intel ME feature while
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/dev/meiX is open. The binding to a specific feature is performed by calling
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:c:macro:`MEI_CONNECT_CLIENT_IOCTL`, which passes the desired GUID.
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The number of instances of an Intel ME feature that can be opened
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at the same time depends on the Intel ME feature, but most of the
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features allow only a single instance.
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The driver is transparent to data that are passed between firmware feature
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and host application.
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Because some of the Intel ME features can change the system
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configuration, the driver by default allows only a privileged
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user to access it.
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The session is terminated calling :c:expr:`close(fd)`.
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A code snippet for an application communicating with Intel AMTHI client:
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In order to support virtualization or sandboxing a trusted supervisor
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can use :c:macro:`MEI_CONNECT_CLIENT_IOCTL_VTAG` to create
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virtual channels with an Intel ME feature. Not all features support
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virtual channels such client with answer EOPNOTSUPP.
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.. code-block:: C
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struct mei_connect_client_data data;
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fd = open(MEI_DEVICE);
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data.d.in_client_uuid = AMTHI_GUID;
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ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &data);
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printf("Ver=%d, MaxLen=%ld\n",
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data.d.in_client_uuid.protocol_version,
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data.d.in_client_uuid.max_msg_length);
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[...]
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write(fd, amthi_req_data, amthi_req_data_len);
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[...]
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read(fd, &amthi_res_data, amthi_res_data_len);
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[...]
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close(fd);
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User space API
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IOCTLs:
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=======
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The Intel MEI Driver supports the following IOCTL commands:
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IOCTL_MEI_CONNECT_CLIENT
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-------------------------
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Connect to firmware Feature/Client.
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.. code-block:: none
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Usage:
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struct mei_connect_client_data client_data;
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ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &client_data);
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Inputs:
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struct mei_connect_client_data - contain the following
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Input field:
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in_client_uuid - GUID of the FW Feature that needs
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to connect to.
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Outputs:
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out_client_properties - Client Properties: MTU and Protocol Version.
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Error returns:
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ENOTTY No such client (i.e. wrong GUID) or connection is not allowed.
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EINVAL Wrong IOCTL Number
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ENODEV Device or Connection is not initialized or ready.
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ENOMEM Unable to allocate memory to client internal data.
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EFAULT Fatal Error (e.g. Unable to access user input data)
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EBUSY Connection Already Open
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:Note:
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max_msg_length (MTU) in client properties describes the maximum
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data that can be sent or received. (e.g. if MTU=2K, can send
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requests up to bytes 2k and received responses up to 2k bytes).
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IOCTL_MEI_CONNECT_CLIENT_VTAG:
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------------------------------
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.. code-block:: none
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Usage:
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struct mei_connect_client_data_vtag client_data_vtag;
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ioctl(fd, IOCTL_MEI_CONNECT_CLIENT_VTAG, &client_data_vtag);
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Inputs:
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struct mei_connect_client_data_vtag - contain the following
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Input field:
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in_client_uuid - GUID of the FW Feature that needs
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to connect to.
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vtag - virtual tag [1, 255]
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Outputs:
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out_client_properties - Client Properties: MTU and Protocol Version.
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Error returns:
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ENOTTY No such client (i.e. wrong GUID) or connection is not allowed.
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EINVAL Wrong IOCTL Number or tag == 0
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ENODEV Device or Connection is not initialized or ready.
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ENOMEM Unable to allocate memory to client internal data.
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EFAULT Fatal Error (e.g. Unable to access user input data)
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EBUSY Connection Already Open
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EOPNOTSUPP Vtag is not supported
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IOCTL_MEI_NOTIFY_SET
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---------------------
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Enable or disable event notifications.
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.. code-block:: none
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Usage:
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uint32_t enable;
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ioctl(fd, IOCTL_MEI_NOTIFY_SET, &enable);
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uint32_t enable = 1;
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or
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uint32_t enable[disable] = 0;
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Error returns:
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EINVAL Wrong IOCTL Number
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ENODEV Device is not initialized or the client not connected
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ENOMEM Unable to allocate memory to client internal data.
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EFAULT Fatal Error (e.g. Unable to access user input data)
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EOPNOTSUPP if the device doesn't support the feature
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:Note:
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The client must be connected in order to enable notification events
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IOCTL_MEI_NOTIFY_GET
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--------------------
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Retrieve event
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.. code-block:: none
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Usage:
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uint32_t event;
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ioctl(fd, IOCTL_MEI_NOTIFY_GET, &event);
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Outputs:
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1 - if an event is pending
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0 - if there is no even pending
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Error returns:
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EINVAL Wrong IOCTL Number
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ENODEV Device is not initialized or the client not connected
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ENOMEM Unable to allocate memory to client internal data.
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EFAULT Fatal Error (e.g. Unable to access user input data)
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EOPNOTSUPP if the device doesn't support the feature
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:Note:
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The client must be connected and event notification has to be enabled
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in order to receive an event
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Supported Chipsets
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==================
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82X38/X48 Express and newer
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linux-mei@linux.intel.com
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