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Diffstat (limited to 'Documentation/networking/nfc.txt')
| -rw-r--r-- | Documentation/networking/nfc.txt | 128 |
1 files changed, 0 insertions, 128 deletions
diff --git a/Documentation/networking/nfc.txt b/Documentation/networking/nfc.txt deleted file mode 100644 index b24c29bdae27..000000000000 --- a/Documentation/networking/nfc.txt +++ /dev/null @@ -1,128 +0,0 @@ -Linux NFC subsystem -=================== - -The Near Field Communication (NFC) subsystem is required to standardize the -NFC device drivers development and to create an unified userspace interface. - -This document covers the architecture overview, the device driver interface -description and the userspace interface description. - -Architecture overview ---------------------- - -The NFC subsystem is responsible for: - - NFC adapters management; - - Polling for targets; - - Low-level data exchange; - -The subsystem is divided in some parts. The 'core' is responsible for -providing the device driver interface. On the other side, it is also -responsible for providing an interface to control operations and low-level -data exchange. - -The control operations are available to userspace via generic netlink. - -The low-level data exchange interface is provided by the new socket family -PF_NFC. The NFC_SOCKPROTO_RAW performs raw communication with NFC targets. - - - +--------------------------------------+ - | USER SPACE | - +--------------------------------------+ - ^ ^ - | low-level | control - | data exchange | operations - | | - | v - | +-----------+ - | AF_NFC | netlink | - | socket +-----------+ - | raw ^ - | | - v v - +---------+ +-----------+ - | rawsock | <--------> | core | - +---------+ +-----------+ - ^ - | - v - +-----------+ - | driver | - +-----------+ - -Device Driver Interface ------------------------ - -When registering on the NFC subsystem, the device driver must inform the core -of the set of supported NFC protocols and the set of ops callbacks. The ops -callbacks that must be implemented are the following: - -* start_poll - setup the device to poll for targets -* stop_poll - stop on progress polling operation -* activate_target - select and initialize one of the targets found -* deactivate_target - deselect and deinitialize the selected target -* data_exchange - send data and receive the response (transceive operation) - -Userspace interface --------------------- - -The userspace interface is divided in control operations and low-level data -exchange operation. - -CONTROL OPERATIONS: - -Generic netlink is used to implement the interface to the control operations. -The operations are composed by commands and events, all listed below: - -* NFC_CMD_GET_DEVICE - get specific device info or dump the device list -* NFC_CMD_START_POLL - setup a specific device to polling for targets -* NFC_CMD_STOP_POLL - stop the polling operation in a specific device -* NFC_CMD_GET_TARGET - dump the list of targets found by a specific device - -* NFC_EVENT_DEVICE_ADDED - reports an NFC device addition -* NFC_EVENT_DEVICE_REMOVED - reports an NFC device removal -* NFC_EVENT_TARGETS_FOUND - reports START_POLL results when 1 or more targets -are found - -The user must call START_POLL to poll for NFC targets, passing the desired NFC -protocols through NFC_ATTR_PROTOCOLS attribute. The device remains in polling -state until it finds any target. However, the user can stop the polling -operation by calling STOP_POLL command. In this case, it will be checked if -the requester of STOP_POLL is the same of START_POLL. - -If the polling operation finds one or more targets, the event TARGETS_FOUND is -sent (including the device id). The user must call GET_TARGET to get the list of -all targets found by such device. Each reply message has target attributes with -relevant information such as the supported NFC protocols. - -All polling operations requested through one netlink socket are stopped when -it's closed. - -LOW-LEVEL DATA EXCHANGE: - -The userspace must use PF_NFC sockets to perform any data communication with -targets. All NFC sockets use AF_NFC: - -struct sockaddr_nfc { - sa_family_t sa_family; - __u32 dev_idx; - __u32 target_idx; - __u32 nfc_protocol; -}; - -To establish a connection with one target, the user must create an -NFC_SOCKPROTO_RAW socket and call the 'connect' syscall with the sockaddr_nfc -struct correctly filled. All information comes from NFC_EVENT_TARGETS_FOUND -netlink event. As a target can support more than one NFC protocol, the user -must inform which protocol it wants to use. - -Internally, 'connect' will result in an activate_target call to the driver. -When the socket is closed, the target is deactivated. - -The data format exchanged through the sockets is NFC protocol dependent. For -instance, when communicating with MIFARE tags, the data exchanged are MIFARE -commands and their responses. - -The first received package is the response to the first sent package and so -on. In order to allow valid "empty" responses, every data received has a NULL -header of 1 byte. |