[PATCH v2 24/29] docs: nfc: convert to ReST

Mauro Carvalho Chehab
2019-06-18T20:54:16Z

Rename the nfc documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
---
Documentation/nfc/index.rst | 11 ++
.../nfc/{nfc-hci.txt => nfc-hci.rst} | 163 ++++++++++--------
.../nfc/{nfc-pn544.txt => nfc-pn544.rst} | 6 +-
3 files changed, 107 insertions(+), 73 deletions(-)
create mode 100644 Documentation/nfc/index.rst
rename Documentation/nfc/{nfc-hci.txt => nfc-hci.rst} (71%)
rename Documentation/nfc/{nfc-pn544.txt => nfc-pn544.rst} (82%)

diff --git a/Documentation/nfc/index.rst b/Documentation/nfc/index.rst
new file mode 100644
index 000000000000..4f4947fce80d
--- /dev/null
+++ b/Documentation/nfc/index.rst
@@ -0,0 +1,11 @@
+:orphan:
+
+========================
+Near Field Communication
+========================
+
+.. toctree::
+ :maxdepth: 1
+
+ nfc-hci
+ nfc-pn544
diff --git a/Documentation/nfc/nfc-hci.txt b/Documentation/nfc/nfc-hci.rst
similarity index 71%
rename from Documentation/nfc/nfc-hci.txt
rename to Documentation/nfc/nfc-hci.rst
index 0dc078cab972..eb8a1a14e919 100644
--- a/Documentation/nfc/nfc-hci.txt
+++ b/Documentation/nfc/nfc-hci.rst
@@ -1,7 +1,9 @@
+========================
HCI backend for NFC Core
+========================

-Author: Eric Lapuyade, Samuel Ortiz
-Contact: eric.lapuyade@intel.com, samuel.ortiz@intel.com
+- Author: Eric Lapuyade, Samuel Ortiz
+- Contact: eric.lapuyade@intel.com, samuel.ortiz@intel.com

General
-------
@@ -24,12 +26,13 @@ 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. 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.
+ can be executing at any given moment.
- one for dispatching received events and commands : nfc_hci_msg_rx_work().

-HCI Session initialization:
----------------------------
+HCI Session initialization
+--------------------------

The Session initialization is an HCI standard which must unfortunately
support proprietary gates. This is the reason why the driver will pass a list
@@ -58,9 +61,9 @@ HCI Management
--------------

A driver would normally register itself with HCI and provide the following
-entry points:
+entry points::

-struct nfc_hci_ops {
+ 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);
@@ -82,38 +85,38 @@ struct nfc_hci_ops {
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.
+ 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 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.
+ 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.
+ 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.
+ 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.
+ perform additional proprietary processing necessary to auto activate the
+ discovered target.
- 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. The data exchange command itself must be sent
-asynchronously.
+ 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. 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
+ 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.
+ 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
@@ -122,20 +125,23 @@ This must be done from a context that can sleep.
PHY Management
--------------

-The physical link (i2c, ...) management is defined by the following structure:
+The physical link (i2c, ...) management is defined by the following structure::

-struct nfc_phy_ops {
+ 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).
+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().

@@ -145,9 +151,9 @@ 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:
+A new llc must implement the following functions::

-struct nfc_llc_ops {
+ 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,
@@ -157,17 +163,25 @@ struct nfc_llc_ops {
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
+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);
+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.
@@ -187,26 +201,32 @@ 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)
-Only when llc_shdlc is used: 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
-timeout.
+
+ Serializes execution of HCI commands.
+
+ Completes execution in case of response timeout.

- HCI Rx worker (MSGRXWQ)
-Dispatches incoming HCI commands or events.
+
+ Dispatches incoming HCI commands or events.

- Syscall context from a userspace call (SYSCALL)
-Any entrypoint in HCI called from NFC Core
+
+ Any entrypoint in HCI called from NFC Core

Workflow executing an HCI command (using shdlc)
-----------------------------------------------

Executing an HCI command can easily be performed synchronously using the
-following API:
+following API::

-int nfc_hci_send_cmd (struct nfc_hci_dev *hdev, u8 gate, u8 cmd,
+ int nfc_hci_send_cmd (struct nfc_hci_dev *hdev, u8 gate, u8 cmd,
const u8 *param, size_t param_len, struct sk_buff **skb)

The API must be invoked from a context that can sleep. Most of the time, this
@@ -234,11 +254,11 @@ 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:
+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)
+ 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.
@@ -268,23 +288,24 @@ went wrong below and know that expected events will probably never happen.
Handling of these errors is done as follows:

- driver (pn544) fails to deliver an incoming frame: it stores the error such
-that any subsequent call to the driver will result in this error. Then it calls
-the standard nfc_shdlc_recv_frame() with a NULL argument to report the problem
-above. shdlc stores a EREMOTEIO sticky status, which will trigger SMW to
-report above in turn.
+ that any subsequent call to the driver will result in this error. Then it
+ calls the standard nfc_shdlc_recv_frame() with a NULL argument to report the
+ problem above. shdlc stores a EREMOTEIO sticky status, which will trigger
+ SMW to report above in turn.

- SMW is basically a background thread to handle incoming and outgoing shdlc
-frames. This thread will also check the shdlc sticky status and report to HCI
-when it discovers it is not able to run anymore because of an unrecoverable
-error that happened within shdlc or below. If the problem occurs during shdlc
-connection, the error is reported through the connect completion.
+ frames. This thread will also check the shdlc sticky status and report to HCI
+ when it discovers it is not able to run anymore because of an unrecoverable
+ error that happened within shdlc or below. If the problem occurs during shdlc
+ connection, the error is reported through the connect completion.

- HCI: if an internal HCI error happens (frame is lost), or HCI is reported an
-error from a lower layer, HCI will either complete the currently executing
-command with that error, or notify NFC Core directly if no command is executing.
+ error from a lower layer, HCI will either complete the currently executing
+ command with that error, or notify NFC Core directly if no command is
+ executing.

- NFC Core: when NFC Core is notified of an error from below and polling is
-active, it will send a tag discovered event with an empty tag list to the user
-space to let it know that the poll operation will never be able to detect a tag.
-If polling is not active and the error was sticky, lower levels will return it
-at next invocation.
+ active, it will send a tag discovered event with an empty tag list to the user
+ space to let it know that the poll operation will never be able to detect a
+ tag. If polling is not active and the error was sticky, lower levels will
+ return it at next invocation.
diff --git a/Documentation/nfc/nfc-pn544.txt b/Documentation/nfc/nfc-pn544.rst
similarity index 82%
rename from Documentation/nfc/nfc-pn544.txt
rename to Documentation/nfc/nfc-pn544.rst
index b36ca14ca2d6..6b2d8aae0c4e 100644
--- a/Documentation/nfc/nfc-pn544.txt
+++ b/Documentation/nfc/nfc-pn544.rst
@@ -1,5 +1,7 @@
-Kernel driver for the NXP Semiconductors PN544 Near Field
-Communication chip
+============================================================================
+Kernel driver for the NXP Semiconductors PN544 Near Field Communication chip
+============================================================================
+

General
-------
--
2.21.0