net: fill in MODULE_DESCRIPTION()s for NFC

W=1 builds now warn if module is built without a MODULE_DESCRIPTION().
Add descriptions to all NFC Controller Interface (NCI) modules.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240108181610.2697017-5-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

NFC: digital: fix possible memory leak in digital_tg_listen_mdaa()

'params' is allocated in digital_tg_listen_mdaa(), but not free when
digital_send_cmd() failed, which will cause memory leak. Fix it by
freeing 'params' if digital_send_cmd() return failed.

Fixes: 1c7a4c24fbfd ("NFC Digital: Add target NFC-DEP support")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

nfc: constify nfc_digital_ops

Neither the core nor the drivers modify the passed pointer to struct
nfc_digital_ops, so make it a pointer to const for correctness and safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

nfc: constify nfc_ops

Neither the core nor the drivers modify the passed pointer to struct
nfc_ops, so make it a pointer to const for correctness and safety.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

NFC: digital: Correct function name in the kerneldoc comments

Fix the following W=1 kernel build warning(s):

net/nfc/digital_core.c:473: warning: expecting prototype for start_poll operation(). Prototype was for digital_start_poll() instead

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net: nfc: Fix kerneldoc warnings

net//nfc/core.c:1046: warning: Function parameter or member 'tx_headroom' not described in 'nfc_allocate_device'
net//nfc/core.c:1046: warning: Function parameter or member 'tx_tailroom' not described in 'nfc_allocate_device'
net//nfc/core.c:198: warning: Excess function parameter 'protocols' description in 'nfc_start_poll'
net//nfc/core.c:198: warning: Function parameter or member 'im_protocols' not described in 'nfc_start_poll'
net//nfc/core.c:198: warning: Function parameter or member 'tm_protocols' not described in 'nfc_start_poll'
net//nfc/core.c:441: warning: Function parameter or member 'mode' not described in 'nfc_deactivate_target'
net//nfc/core.c:711: warning: Function parameter or member 'dev' not described in 'nfc_alloc_send_skb'
net//nfc/core.c:711: warning: Function parameter or member 'err' not described in 'nfc_alloc_send_skb'
net//nfc/core.c:711: warning: Function parameter or member 'flags' not described in 'nfc_alloc_send_skb'
net//nfc/core.c:711: warning: Function parameter or member 'sk' not described in 'nfc_alloc_send_skb'
net//nfc/digital_core.c:470: warning: Function parameter or member 'im_protocols' not described in 'digital_start_poll'
net//nfc/digital_core.c:470: warning: Function parameter or member 'nfc_dev' not described in 'digital_start_poll'
net//nfc/digital_core.c:470: warning: Function parameter or member 'tm_protocols' not described in 'digital_start_poll'
net//nfc/nci/core.c:1119: warning: Function parameter or member 'tx_headroom' not described in 'nci_allocate_device'
net//nfc/nci/core.c:1119: warning: Function parameter or member 'tx_tailroom' not described in 'nci_allocate_device'

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20201028005653.930467-1-andrew@lunn.ch
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 288

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms and conditions of the gnu general public license
version 2 as published by the free software foundation this program
is distributed in the hope it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 263 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.208660670@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

NFC: digital: Abort cmd when deactivating target

When deactivating an active target, the outstanding command should
be aborted.

Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Delete an error message for memory allocation failure

Omit an extra message for a memory allocation failure in this function.

This issue was detected by using the Coccinelle software.

Link: http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Improve a size determination in four functions

Replace the specification of four data structures by pointer dereferences
as the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style convention.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

networking: add and use skb_put_u8()

Joe and Bjørn suggested that it'd be nicer to not have the
cast in the fairly common case of doing
*(u8 *)skb_put(skb, 1) = c;

Add skb_put_u8() for this case, and use it across the code,
using the following spatch:

@@
expression SKB, C, S;
typedef u8;
identifier fn = {skb_put};
fresh identifier fn2 = fn ## "_u8";
@@
- *(u8 *)fn(SKB, S) = C;
+ fn2(SKB, C);

Note that due to the "S", the spatch isn't perfect, it should
have checked that S is 1, but there's also places that use a
sizeof expression like sizeof(var) or sizeof(u8) etc. Turns
out that nobody ever did something like
*(u8 *)skb_put(skb, 2) = c;

which would be wrong anyway since the second byte wouldn't be
initialized.

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

networking: make skb_put & friends return void pointers

It seems like a historic accident that these return unsigned char *,
and in many places that means casts are required, more often than not.

Make these functions (skb_put, __skb_put and pskb_put) return void *
and remove all the casts across the tree, adding a (u8 *) cast only
where the unsigned char pointer was used directly, all done with the
following spatch:

@@
expression SKB, LEN;
typedef u8;
identifier fn = { skb_put, __skb_put };
@@
- *(fn(SKB, LEN))
+ *(u8 *)fn(SKB, LEN)

@@
expression E, SKB, LEN;
identifier fn = { skb_put, __skb_put };
type T;
@@
- E = ((T *)(fn(SKB, LEN)))
+ E = fn(SKB, LEN)

which actually doesn't cover pskb_put since there are only three
users overall.

A handful of stragglers were converted manually, notably a macro in
drivers/isdn/i4l/isdn_bsdcomp.c and, oddly enough, one of the many
instances in net/bluetooth/hci_sock.c. In the former file, I also
had to fix one whitespace problem spatch introduced.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

NFC: digital: Abort last command when dep link goes down

With this patch, the Digital Protocol layer abort the last issued
command when the dep link goes down. That way it does not have to wait
for the driver to reply with a timeout error before sending a new
command (i.e. a start poll command if constant polling is on).

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Set the command pending flag

There is a flag in the command structure indicating that this command is
pending. It was checked before sending the command to not send the same
command twice but it was actually never set. This is now fixed.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Call pending command callbacks at device unregister

With this patch, when freeing the command queue in the module unregister
function, the callbacks of the commands still queued are called with a
ENODEV error. This gives a chance to the command issuer to free any
memory it could have allocate.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add a delay between poll cycles

This replaces the polling work struct with a delayed work struct and add
a 10 ms delay between 2 poll cycles. This avoids to flood the device
with 'switch off'/'switch on' commands.

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add Type4A tags support

The definition of DIGITAL_PROTO_NFCA_RF_TECH is modified to support
ISO14443 Type4A tags. Without this change it is not possible to start
polling for ISO14443 Type4A tags from the initiator side.

Signed-off-by: Shikha Singh <shikha.singh@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: netlink: Add mode parameter to deactivate_target functions

In order to manage in a better way the nci poll mode state machine,
add mode parameter to deactivate_target functions.
This way we can manage different target state.
mode parameter make sense only in nci core.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add 'tg_listen_md' and 'tg_get_rf_tech' driver hooks

The digital layer of the NFC subsystem currently
supports a 'tg_listen_mdaa' driver hook that supports
devices that can do mode detection and automatic
anticollision. However, there are some devices that
can do mode detection but not automatic anitcollision
so add the 'tg_listen_md' hook to support those devices.

In order for the digital layer to get the RF technology
detected by the device from the driver, add the
'tg_get_rf_tech' hook. It is only valid to call this
hook immediately after a successful call to 'tg_listen_md'.

CC: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Clear poll_tech_count before activating target

Currently, digital_target_found() has a race between
the events started by calling nfc_targets_found()
(which ultimately expect ddev->poll_tech_count to be
zero) and setting ddev->poll_tech_count to zero after
the call to nfc_targets_found(). When the race is
"lost" (i.e., ddev->poll_tech_count is found to not
be zero by the events started by nfc_targets_found()),
an error message is printed and the target is not found.
A similar race exists when digital_tg_recv_atr_req()
calls nfc_tm_activated().

Fix this by first saving the current value of
ddev->poll_tech_count and then clearing it before
calling nfc_targets_found()/nfc_tm_activated().
Clearing ddev->poll_tech_count before calling
nfc_targets_found()/nfc_tm_activated() eliminates
the race. Saving the value is required so it can be
restored when nfc_targets_found()/nfc_tm_activated()
fails and polling needs to continue.

Acked-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Randomize poll cycles

This change adds some entropy to polling cycles, choosing the next
polling rf technology randomly. This reflects the change done in the
pn533 driver, avoiding possible infinite loop for devices that export 2
targets on 2 different modulations. If the first target is not
readable, we will stay in an error loop for ever.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add support for ISO/IEC 14443-B Protocol

Add support for the ISO/IEC 14443-B protocol and Type 4B tags.
It is expected that there will be only one tag within range so the full
anticollision scheme is not implemented. Only the SENSB_REQ/SENSB_RES
and ATTRIB_REQ/ATTRIB_RES are implemented.

CC: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Rename Type V tags to Type 5 tags

According to the latest draft specification from
the NFC-V committee, ISO/IEC 15693 tags will be
referred to as "Type 5" tags and not "Type V"
tags anymore. Make the code reflect the new
terminology.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Use matching_[im|tm]_protocols to check with NFC protocols masks

This ensures we won't add polling function to the table of polling technologies
for non-supported protocols.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Fix a possible memory leak

This fixes a memory leak issue that may occur if data sending fails in
initiator mode. The data_exch structure was not released in case of
error.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add missing break in switch statement

There was a missing break making the digital stack configured for
ISO1443 target instead of ISO15693.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add ISO-DEP support for data exchange

When a type 4A target is activated, this change adds the ISO-DEP SoD
when sending frames and removes it when receiving responses. Chaining
is not supported so sent frames are rejected if they exceed remote FSC
bytes.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add poll support for type 4A tag platform

This adds support for ATS request and response handling for type 4A tag
activation.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add Digital Layer support for ISO/IEC 15693

Add support for ISO/IEC 15693 to the digital layer. The code
currently uses single-slot anticollision only since the digital
layer infrastructure only supports one tag per adapter (making
it pointless to do 16-slot anticollision).

The code uses two new framing types:
'NFC_DIGITAL_FRAMING_ISO15693_INVENTORY' and
'NFC_DIGITAL_FRAMING_ISO15693_TVT'. The former is used to
tell the driver to prepare for an Inventory command and the
ensuing anticollision sequence. The latter is used to tell
the driver that the anticollision sequence is over and to
prepare for non-inventory commands.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Set current target active on activate_target() call

The curr_protocol field of nfc_digital_dev structure used to determine
if a target is currently active was set too soon, immediately when a
target is found. This is not good since there is no other way than
deactivate_target() to reset curr_protocol and if activate_target() is
not called, the target remains active and it's not possible to put the
device in poll mode anymore.

With this patch curr_protocol is set when nfc core activates a target,
puts a device up, or when an ATR_REQ is received in target mode.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Add newline to pr_* calls

We do not add the newline to the pr_fmt macro, in order to give more
flexibility to the caller and to keep the logging style consistent with
the rest of the NFC and kernel code.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: digital: Remove PR_ERR and PR_DBG macros

They can be replaced by the standard pr_err and pr_debug one after
defining the right pr_fmt macro.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC Digital: Add target NFC-DEP support

This adds support for NFC-DEP target mode for NFC-A and NFC-F
technologies.

If the driver provides it, the stack uses an automatic mode for
technology detection and automatic anti-collision. Otherwise the stack
tries to use non-automatic synchronization and listens for SENS_REQ and
SENSF_REQ commands.

The detection, activation, and data exchange procedures work exactly
the same way as in initiator mode, as described in the previous
commits, except that the digital stack waits for commands and sends
responses back to the peer device.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC Digital: Add initiator NFC-DEP support

This adds support for NFC-DEP protocol in initiator mode for NFC-A and
NFC-F technologies.

When a target is detected, the process flow is as follow:

For NFC-A technology:
1 - The digital stack receives a SEL_RES as the reply of the SEL_REQ
command.
2 - If b7 of SEL_RES is set, the peer device is configure for NFC-DEP
protocol. NFC core is notified through nfc_targets_found().
Execution continues at step 4.
3 - Otherwise, it's a tag and the NFC core is notified. Detection
ends.
4 - The digital stacks sends an ATR_REQ command containing a randomly
generated NFCID3 and the general bytes obtained from the LLCP layer
of NFC core.

For NFC-F technology:
1 - The digital stack receives a SENSF_RES as the reply of the
SENSF_REQ command.
2 - If B1 and B2 of NFCID2 are 0x01 and 0xFE respectively, the peer
device is configured for NFC-DEP protocol. NFC core is notified
through nfc_targets_found(). Execution continues at step 4.
3 - Otherwise it's a type 3 tag. NFC core is notified. Detection
ends.
4 - The digital stacks sends an ATR_REQ command containing the NFC-F
NFCID2 as NFCID3 and the general bytes obtained from the LLCP layer
of NFC core.

For both technologies:
5 - The digital stacks receives the ATR_RES response containing the
NFCID3 and the general bytes of the peer device.
6 - The digital stack notifies NFC core that the DEP link is up through
nfc_dep_link_up().
7 - The NFC core performs data exchange through tm_transceive().
8 - The digital stack sends a DEP_REQ command containing an I PDU with
the data from NFC core.
9 - The digital stack receives a DEP_RES command
10 - If the DEP_RES response contains a supervisor PDU with timeout
extension request (RTOX) the digital stack sends a DEP_REQ
command containing a supervisor PDU acknowledging the RTOX
request. The execution continues at step 9.
11 - If the DEP_RES response contains an I PDU, the response data is
passed back to NFC core through the response callback. The
execution continues at step 8.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC Digital: Add NFC-F technology support

This adds polling support for NFC-F technology at 212 kbits/s and 424
kbits/s. A user space application like neard can send type 3 tag
commands through the NFC core.

Process flow for NFC-F detection is as follow:

1 - The digital stack sends the SENSF_REQ command to the NFC device.
2 - A peer device replies with a SENSF_RES response.
3 - The digital stack notifies the NFC core of the presence of a
target in the operation field and passes the target NFCID2.

This also adds support for CRC calculation of type CRC-F. The CRC
calculation is handled by the digital stack if the NFC device doesn't
support it.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC Digital: Add NFC-A technology support

This adds support for NFC-A technology at 106 kbits/s. The stack can
detect tags of type 1 and 2. There is no support for collision
detection. Tags can be read and written by using a user space
application or a daemon like neard.

The flow of polling operations for NFC-A detection is as follow:

1 - The digital stack sends the SENS_REQ command to the NFC device.
2 - The NFC device receives a SENS_RES response from a peer device and
passes it to the digital stack.
3 - If the SENS_RES response identifies a type 1 tag, detection ends.
NFC core is notified through nfc_targets_found().
4 - Otherwise, the digital stack sets the cascade level of NFCID1 to
CL1 and sends the SDD_REQ command.
5 - The digital stack selects SEL_CMD and SEL_PAR according to the
cascade level and sends the SDD_REQ command.
4 - The digital stack receives a SDD_RES response for the cascade level
passed in the SDD_REQ command.
5 - The digital stack analyses (part of) NFCID1 and verify BCC.
6 - The digital stack sends the SEL_REQ command with the NFCID1
received in the SDD_RES.
6 - The peer device replies with a SEL_RES response
7 - Detection ends if NFCID1 is complete. NFC core notified of new
target by nfc_targets_found().
8 - If NFCID1 is not complete, the cascade level is incremented (up
to and including CL3) and the execution continues at step 5 to
get the remaining bytes of NFCID1.

Once target detection is done, type 1 and 2 tag commands must be
handled by a user space application (i.e neard) through the NFC core.
Responses for type 1 tag are returned directly to user space via NFC
core.
Responses of type 2 commands are handled differently. The digital stack
doesn't analyse the type of commands sent through im_transceive() and
must differentiate valid responses from error ones.
The response process flow is as follow:

1 - If the response length is 16 bytes, it is a valid response of a
READ command. the packet is returned to the NFC core through the
callback passed to im_transceive(). Processing stops.
2 - If the response is 1 byte long and is a ACK byte (0x0A), it is a
valid response of a WRITE command for example. First packet byte
is set to 0 for no-error and passed back to the NFC core.
Processing stops.
3 - Any other response is treated as an error and -EIO error code is
returned to the NFC core through the response callback.

Moreover, since the driver can't differentiate success response from a
NACK response, the digital stack has to handle CRC calculation.

Thus, this patch also adds support for CRC calculation. If the driver
doesn't handle it, the digital stack will calculate CRC and will add it
to sent frames. CRC will also be checked and removed from received
frames. Pointers to the correct CRC calculation functions are stored in
the digital stack device structure when a target is detected. This
avoids the need to check the current target type for every call to
im_transceive() and for every response received from a peer device.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC Digital: Implement driver commands mechanism

This implements the mechanism used to send commands to the driver in
initiator mode through in_send_cmd().

Commands are serialized and sent to the driver by using a work item
on the system workqueue. Responses are handled asynchronously by
another work item. Once the digital stack receives the response through
the command_complete callback, the next command is sent to the driver.

This also implements the polling mechanism. It's handled by a work item
cycling on all supported protocols. The start poll command for a given
protocol is sent to the driver using the mechanism described above.
The process continues until a peer is discovered or stop_poll is
called. This patch implements the poll function for NFC-A that sends a
SENS_REQ command and waits for the SENS_RES response.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

NFC: Digital Protocol stack implementation

This is the initial commit of the NFC Digital Protocol stack
implementation.

It offers an interface for devices that don't have an embedded NFC
Digital protocol stack. The driver instantiates the digital stack by
calling nfc_digital_allocate_device(). Within the nfc_digital_ops
structure, the driver specifies a set of function pointers for driver
operations. These functions must be implemented by the driver and are:

in_configure_hw:
Hardware configuration for RF technology and communication framing in
initiator mode. This is a synchronous function.

in_send_cmd:
Initiator mode data exchange using RF technology and framing previously
set with in_configure_hw. The peer response is returned through
callback cb. If an io error occurs or the peer didn't reply within the
specified timeout (ms), the error code is passed back through the resp
pointer. This is an asynchronous function.

tg_configure_hw:
Hardware configuration for RF technology and communication framing in
target mode. This is a synchronous function.

tg_send_cmd:
Target mode data exchange using RF technology and framing previously
set with tg_configure_hw. The peer next command is returned through
callback cb. If an io error occurs or the peer didn't reply within the
specified timeout (ms), the error code is passed back through the resp
pointer. This is an asynchronous function.

tg_listen:
Put the device in listen mode waiting for data from the peer device.
This is an asynchronous function.

tg_listen_mdaa:
If supported, put the device in automatic listen mode with mode
detection and automatic anti-collision. In this mode, the device
automatically detects the RF technology and executes the
anti-collision detection using the command responses specified in
mdaa_params. The mdaa_params structure contains SENS_RES, NFCID1, and
SEL_RES for 106A RF tech. NFCID2 and system code (sc) for 212F and
424F. The driver returns the NFC-DEP ATR_REQ command through cb. The
digital stack deducts the RF tech by analyzing the SoD of the frame
containing the ATR_REQ command. This is an asynchronous function.

switch_rf:
Turns device radio on or off. The stack does not call explicitly
switch_rf to turn the radio on. A call to in|tg_configure_hw must turn
the device radio on.

abort_cmd:
Discard the last sent command.

Then the driver registers itself against the digital stack by using
nfc_digital_register_device() which in turn registers the digital stack
against the NFC core layer. The digital stack implements common NFC
operations like dev_up(), dev_down(), start_poll(), stop_poll(), etc.

This patch is only a skeleton and NFC operations are just stubs.

Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>