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| -rw-r--r-- | Documentation/driver-api/mei/mei.rst | 213 |
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diff --git a/Documentation/driver-api/mei/mei.rst b/Documentation/driver-api/mei/mei.rst new file mode 100644 index 000000000..4f2ced4cc --- /dev/null +++ b/Documentation/driver-api/mei/mei.rst @@ -0,0 +1,213 @@ +.. SPDX-License-Identifier: GPL-2.0 + +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 and security features. +The actual 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, actually multiple PCI devices might be exposed. +The Intel MEI Driver is in charge of the communication channel between +a host application and the Intel ME features. + +Each Intel ME feature, or Intel ME Client is addressed by a unique GUID and +each client has its own protocol. The protocol is message-based with a +header and payload up to maximal number of bytes advertised by the client, +upon connection. + +Intel MEI Driver +================ + +The driver exposes a character device with device nodes /dev/meiX. + +An application maintains communication with an Intel ME feature while +/dev/meiX is open. The binding to a specific feature is performed by calling +:c:macro:`MEI_CONNECT_CLIENT_IOCTL`, which passes the desired GUID. +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 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. + +The session is terminated calling :c:expr:`close(fd)`. + +A code snippet for an application communicating with Intel AMTHI client: + +In order to support virtualization or sandboxing a trusted supervisor +can use :c:macro:`MEI_CONNECT_CLIENT_IOCTL_VTAG` to create +virtual channels with an Intel ME feature. Not all features support +virtual channels such client with answer EOPNOTSUPP. + +.. code-block:: C + + struct mei_connect_client_data data; + fd = open(MEI_DEVICE); + + data.d.in_client_uuid = AMTHI_GUID; + + 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); + + +User space API + +IOCTLs: +======= + +The Intel MEI Driver supports the following IOCTL commands: + +IOCTL_MEI_CONNECT_CLIENT +------------------------- +Connect to firmware Feature/Client. + +.. code-block:: none + + Usage: + + struct mei_connect_client_data client_data; + + ioctl(fd, IOCTL_MEI_CONNECT_CLIENT, &client_data); + + Inputs: + + struct mei_connect_client_data - contain the following + Input field: + + in_client_uuid - GUID of the FW Feature that needs + to connect to. + Outputs: + out_client_properties - Client Properties: MTU and Protocol Version. + + Error returns: + + ENOTTY No such client (i.e. wrong GUID) or connection is not allowed. + EINVAL Wrong IOCTL Number + ENODEV Device or Connection is not initialized or ready. + ENOMEM Unable to allocate memory to client internal data. + EFAULT Fatal Error (e.g. Unable to access user input data) + EBUSY Connection Already Open + +:Note: + 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_CONNECT_CLIENT_VTAG: +------------------------------ + +.. code-block:: none + + Usage: + + struct mei_connect_client_data_vtag client_data_vtag; + + ioctl(fd, IOCTL_MEI_CONNECT_CLIENT_VTAG, &client_data_vtag); + + Inputs: + + struct mei_connect_client_data_vtag - contain the following + Input field: + + in_client_uuid - GUID of the FW Feature that needs + to connect to. + vtag - virtual tag [1, 255] + + Outputs: + out_client_properties - Client Properties: MTU and Protocol Version. + + Error returns: + + ENOTTY No such client (i.e. wrong GUID) or connection is not allowed. + EINVAL Wrong IOCTL Number or tag == 0 + ENODEV Device or Connection is not initialized or ready. + ENOMEM Unable to allocate memory to client internal data. + EFAULT Fatal Error (e.g. Unable to access user input data) + EBUSY Connection Already Open + EOPNOTSUPP Vtag is not supported + +IOCTL_MEI_NOTIFY_SET +--------------------- +Enable or disable event notifications. + + +.. code-block:: none + + Usage: + + uint32_t enable; + + ioctl(fd, IOCTL_MEI_NOTIFY_SET, &enable); + + + 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 + +:Note: + The client must be connected in order to enable notification events + + +IOCTL_MEI_NOTIFY_GET +-------------------- +Retrieve event + +.. code-block:: none + + 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 + +:Note: + The client must be connected and event notification has to be enabled + in order to receive an event + + + +Supported Chipsets +================== +82X38/X48 Express and newer + +linux-mei@linux.intel.com |