NFC: update HCI documentation
Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
This commit is contained in:
parent
a0f36536ac
commit
2ad554a502
|
@ -17,10 +17,12 @@ HCI
|
|||
HCI registers as an nfc device with NFC Core. Requests coming from userspace are
|
||||
routed through netlink sockets to NFC Core and then to HCI. From this point,
|
||||
they are translated in a sequence of HCI commands sent to the HCI layer in the
|
||||
host controller (the chip). The sending context blocks while waiting for the
|
||||
response to arrive.
|
||||
host controller (the chip). Commands can be executed synchronously (the sending
|
||||
context blocks waiting for response) or asynchronously (the response is returned
|
||||
from HCI Rx context).
|
||||
HCI events can also be received from the host controller. They will be handled
|
||||
and a translation will be forwarded to NFC Core as needed.
|
||||
and a translation will be forwarded to NFC Core as needed. There are hooks to
|
||||
let the HCI driver handle proprietary events or override standard behavior.
|
||||
HCI uses 2 execution contexts:
|
||||
- one for executing commands : nfc_hci_msg_tx_work(). Only one command
|
||||
can be executing at any given moment.
|
||||
|
@ -33,6 +35,8 @@ The Session initialization is an HCI standard which must unfortunately
|
|||
support proprietary gates. This is the reason why the driver will pass a list
|
||||
of proprietary gates that must be part of the session. HCI will ensure all
|
||||
those gates have pipes connected when the hci device is set up.
|
||||
In case the chip supports pre-opened gates and pseudo-static pipes, the driver
|
||||
can pass that information to HCI core.
|
||||
|
||||
HCI Gates and Pipes
|
||||
-------------------
|
||||
|
@ -46,6 +50,13 @@ without knowing the pipe connected to it.
|
|||
Driver interface
|
||||
----------------
|
||||
|
||||
A driver is generally written in two parts : the physical link management and
|
||||
the HCI management. This makes it easier to maintain a driver for a chip that
|
||||
can be connected using various phy (i2c, spi, ...)
|
||||
|
||||
HCI Management
|
||||
--------------
|
||||
|
||||
A driver would normally register itself with HCI and provide the following
|
||||
entry points:
|
||||
|
||||
|
@ -53,58 +64,113 @@ struct nfc_hci_ops {
|
|||
int (*open)(struct nfc_hci_dev *hdev);
|
||||
void (*close)(struct nfc_hci_dev *hdev);
|
||||
int (*hci_ready) (struct nfc_hci_dev *hdev);
|
||||
int (*xmit)(struct nfc_hci_dev *hdev, struct sk_buff *skb);
|
||||
int (*start_poll)(struct nfc_hci_dev *hdev, u32 protocols);
|
||||
int (*target_from_gate)(struct nfc_hci_dev *hdev, u8 gate,
|
||||
struct nfc_target *target);
|
||||
int (*xmit) (struct nfc_hci_dev *hdev, struct sk_buff *skb);
|
||||
int (*start_poll) (struct nfc_hci_dev *hdev,
|
||||
u32 im_protocols, u32 tm_protocols);
|
||||
int (*dep_link_up)(struct nfc_hci_dev *hdev, struct nfc_target *target,
|
||||
u8 comm_mode, u8 *gb, size_t gb_len);
|
||||
int (*dep_link_down)(struct nfc_hci_dev *hdev);
|
||||
int (*target_from_gate) (struct nfc_hci_dev *hdev, u8 gate,
|
||||
struct nfc_target *target);
|
||||
int (*complete_target_discovered) (struct nfc_hci_dev *hdev, u8 gate,
|
||||
struct nfc_target *target);
|
||||
int (*data_exchange) (struct nfc_hci_dev *hdev,
|
||||
struct nfc_target *target,
|
||||
struct sk_buff *skb, struct sk_buff **res_skb);
|
||||
int (*im_transceive) (struct nfc_hci_dev *hdev,
|
||||
struct nfc_target *target, struct sk_buff *skb,
|
||||
data_exchange_cb_t cb, void *cb_context);
|
||||
int (*tm_send)(struct nfc_hci_dev *hdev, struct sk_buff *skb);
|
||||
int (*check_presence)(struct nfc_hci_dev *hdev,
|
||||
struct nfc_target *target);
|
||||
int (*event_received)(struct nfc_hci_dev *hdev, u8 gate, u8 event,
|
||||
struct sk_buff *skb);
|
||||
};
|
||||
|
||||
- open() and close() shall turn the hardware on and off.
|
||||
- hci_ready() is an optional entry point that is called right after the hci
|
||||
session has been set up. The driver can use it to do additional initialization
|
||||
that must be performed using HCI commands.
|
||||
- xmit() shall simply write a frame to the chip.
|
||||
- xmit() shall simply write a frame to the physical link.
|
||||
- start_poll() is an optional entrypoint that shall set the hardware in polling
|
||||
mode. This must be implemented only if the hardware uses proprietary gates or a
|
||||
mechanism slightly different from the HCI standard.
|
||||
- dep_link_up() is called after a p2p target has been detected, to finish
|
||||
the p2p connection setup with hardware parameters that need to be passed back
|
||||
to nfc core.
|
||||
- dep_link_down() is called to bring the p2p link down.
|
||||
- target_from_gate() is an optional entrypoint to return the nfc protocols
|
||||
corresponding to a proprietary gate.
|
||||
- complete_target_discovered() is an optional entry point to let the driver
|
||||
perform additional proprietary processing necessary to auto activate the
|
||||
discovered target.
|
||||
- data_exchange() must be implemented by the driver if proprietary HCI commands
|
||||
- im_transceive() must be implemented by the driver if proprietary HCI commands
|
||||
are required to send data to the tag. Some tag types will require custom
|
||||
commands, others can be written to using the standard HCI commands. The driver
|
||||
can check the tag type and either do proprietary processing, or return 1 to ask
|
||||
for standard processing.
|
||||
for standard processing. The data exchange command itself must be sent
|
||||
asynchronously.
|
||||
- tm_send() is called to send data in the case of a p2p connection
|
||||
- check_presence() is an optional entry point that will be called regularly
|
||||
by the core to check that an activated tag is still in the field. If this is
|
||||
not implemented, the core will not be able to push tag_lost events to the user
|
||||
space
|
||||
- event_received() is called to handle an event coming from the chip. Driver
|
||||
can handle the event or return 1 to let HCI attempt standard processing.
|
||||
|
||||
On the rx path, the driver is responsible to push incoming HCP frames to HCI
|
||||
using nfc_hci_recv_frame(). HCI will take care of re-aggregation and handling
|
||||
This must be done from a context that can sleep.
|
||||
|
||||
SHDLC
|
||||
-----
|
||||
PHY Management
|
||||
--------------
|
||||
|
||||
Most chips use shdlc to ensure integrity and delivery ordering of the HCP
|
||||
frames between the host controller (the chip) and hosts (entities connected
|
||||
to the chip, like the cpu). In order to simplify writing the driver, an shdlc
|
||||
layer is available for use by the driver.
|
||||
When used, the driver actually registers with shdlc, and shdlc will register
|
||||
with HCI. HCI sees shdlc as the driver and thus send its HCP frames
|
||||
through shdlc->xmit.
|
||||
SHDLC adds a new execution context (nfc_shdlc_sm_work()) to run its state
|
||||
machine and handle both its rx and tx path.
|
||||
The physical link (i2c, ...) management is defined by the following struture:
|
||||
|
||||
struct nfc_phy_ops {
|
||||
int (*write)(void *dev_id, struct sk_buff *skb);
|
||||
int (*enable)(void *dev_id);
|
||||
void (*disable)(void *dev_id);
|
||||
};
|
||||
|
||||
enable(): turn the phy on (power on), make it ready to transfer data
|
||||
disable(): turn the phy off
|
||||
write(): Send a data frame to the chip. Note that to enable higher
|
||||
layers such as an llc to store the frame for re-emission, this function must
|
||||
not alter the skb. It must also not return a positive result (return 0 for
|
||||
success, negative for failure).
|
||||
|
||||
Data coming from the chip shall be sent directly to nfc_hci_recv_frame().
|
||||
|
||||
LLC
|
||||
---
|
||||
|
||||
Communication between the CPU and the chip often requires some link layer
|
||||
protocol. Those are isolated as modules managed by the HCI layer. There are
|
||||
currently two modules : nop (raw transfert) and shdlc.
|
||||
A new llc must implement the following functions:
|
||||
|
||||
struct nfc_llc_ops {
|
||||
void *(*init) (struct nfc_hci_dev *hdev, xmit_to_drv_t xmit_to_drv,
|
||||
rcv_to_hci_t rcv_to_hci, int tx_headroom,
|
||||
int tx_tailroom, int *rx_headroom, int *rx_tailroom,
|
||||
llc_failure_t llc_failure);
|
||||
void (*deinit) (struct nfc_llc *llc);
|
||||
int (*start) (struct nfc_llc *llc);
|
||||
int (*stop) (struct nfc_llc *llc);
|
||||
void (*rcv_from_drv) (struct nfc_llc *llc, struct sk_buff *skb);
|
||||
int (*xmit_from_hci) (struct nfc_llc *llc, struct sk_buff *skb);
|
||||
};
|
||||
|
||||
- init() : allocate and init your private storage
|
||||
- deinit() : cleanup
|
||||
- start() : establish the logical connection
|
||||
- stop () : terminate the logical connection
|
||||
- rcv_from_drv() : handle data coming from the chip, going to HCI
|
||||
- xmit_from_hci() : handle data sent by HCI, going to the chip
|
||||
|
||||
The llc must be registered with nfc before it can be used. Do that by
|
||||
calling nfc_llc_register(const char *name, struct nfc_llc_ops *ops);
|
||||
|
||||
Again, note that the llc does not handle the physical link. It is thus very
|
||||
easy to mix any physical link with any llc for a given chip driver.
|
||||
|
||||
Included Drivers
|
||||
----------------
|
||||
|
@ -117,10 +183,12 @@ Execution Contexts
|
|||
|
||||
The execution contexts are the following:
|
||||
- IRQ handler (IRQH):
|
||||
fast, cannot sleep. stores incoming frames into an shdlc rx queue
|
||||
fast, cannot sleep. sends incoming frames to HCI where they are passed to
|
||||
the current llc. In case of shdlc, the frame is queued in shdlc rx queue.
|
||||
|
||||
- SHDLC State Machine worker (SMW)
|
||||
handles shdlc rx & tx queues. Dispatches HCI cmd responses.
|
||||
Only when llc_shdlc is used: handles shdlc rx & tx queues.
|
||||
Dispatches HCI cmd responses.
|
||||
|
||||
- HCI Tx Cmd worker (MSGTXWQ)
|
||||
Serializes execution of HCI commands. Completes execution in case of response
|
||||
|
@ -166,6 +234,15 @@ waiting command execution. Response processing involves invoking the completion
|
|||
callback that was provided by nfc_hci_msg_tx_work() when it sent the command.
|
||||
The completion callback will then wake the syscall context.
|
||||
|
||||
It is also possible to execute the command asynchronously using this API:
|
||||
|
||||
static int nfc_hci_execute_cmd_async(struct nfc_hci_dev *hdev, u8 pipe, u8 cmd,
|
||||
const u8 *param, size_t param_len,
|
||||
data_exchange_cb_t cb, void *cb_context)
|
||||
|
||||
The workflow is the same, except that the API call returns immediately, and
|
||||
the callback will be called with the result from the SMW context.
|
||||
|
||||
Workflow receiving an HCI event or command
|
||||
------------------------------------------
|
||||
|
||||
|
|
Loading…
Reference in New Issue