NFC: Driver for NXP Semiconductors PN544 NFC chip.

Kernel driver for the NXP Semiconductors PN544 Near Field

Communication chip

Author: Jari Vanhala

Contact: Matti Aaltonen (matti.j.aaltonen at nokia.com)

General

-------

The PN544 is an integrated transmission module for contactless

communication. The driver goes under drives/nfc/ and is compiled as a

module named "pn544". It registers a misc device and creates a device

file named "/dev/pn544".

Host Interfaces: I2C, SPI and HSU, this driver supports currently only I2C.

The Interface

-------------

The driver offers a sysfs interface for a hardware test and an IOCTL

interface for selecting between two operating modes. There are read,

write and poll functions for transferring messages. The two operating

modes are the normal (HCI) mode and the firmware update mode.

PN544 is controlled by sending messages from the userspace to the

chip. The main function of the driver is just to pass those messages

without caring about the message content.

Protocols

---------

In the normal (HCI) mode and in the firmware update mode read and

write functions behave a bit differently because the message formats

or the protocols are different.

In the normal (HCI) mode the protocol used is derived from the ETSI

HCI specification. The firmware is updated using a specific protocol,

which is different from HCI.

HCI messages consist of an eight bit header and the message body. The

header contains the message length. Maximum size for an HCI message is

33. In HCI mode sent messages are tested for a correct

checksum. Firmware update messages have the length in the second (MSB)

and third (LSB) bytes of the message. The maximum FW message length is

1024 bytes.

For the ETSI HCI specification see

http://www.etsi.org/WebSite/Technologies/ProtocolSpecification.aspx

The Hardware Test

-----------------

The idea of the test is that it can performed by reading from the

corresponding sysfs file. The test is implemented in the board file

and it should test that PN544 can be put into the firmware update

mode. If the test is not implemented the sysfs file does not get

created.

Example:

> cat /sys/module/pn544/drivers/i2c\:pn544/3-002b/nfc_test

1

Normal Operation

----------------

PN544 is powered up when the device file is opened, otherwise it's

turned off. Only one instance can use the device at a time.

Userspace applications control PN544 with HCI messages. The hardware

sends an interrupt when data is available for reading. Data is

physically read when the read function is called by a userspace

application. Poll() checks the read interrupt state. Configuration and

self testing are also done from the userspace using read and write.

Example platform data:

static int rx71_pn544_nfc_request_resources(struct i2c_client *client)

{

	/* Get and setup the HW resources for the device */

}

static void rx71_pn544_nfc_free_resources(void)

{

	/* Release the HW resources */

}

static void rx71_pn544_nfc_enable(int fw)

{

	/* Turn the device on */

}

static int rx71_pn544_nfc_test(void)

{

	/*

	 * Put the device into the FW update mode

	 * and then back to the normal mode.

	 * Check the behavior and return one on success,

	 * zero on failure.

	 */

}

static void rx71_pn544_nfc_disable(void)

{

	/* turn the power off */

}

static struct pn544_nfc_platform_data rx71_nfc_data = {

	.request_resources = rx71_pn544_nfc_request_resources,

	.free_resources = rx71_pn544_nfc_free_resources,

	.enable = rx71_pn544_nfc_enable,

	.test = rx71_pn544_nfc_test,

	.disable = rx71_pn544_nfc_disable,

};

source "drivers/leds/Kconfig"

source "drivers/nfc/Kconfig"

source "drivers/accessibility/Kconfig"

source "drivers/infiniband/Kconfig"

obj-y				+= serial/

obj-$(CONFIG_PARPORT)		+= parport/

obj-y				+= base/ block/ misc/ mfd/

obj-y				+= base/ block/ misc/ mfd/ nfc/

obj-$(CONFIG_NUBUS)		+= nubus/

obj-y				+= macintosh/

obj-$(CONFIG_IDE)		+= ide/

#

# Near Field Communication (NFC) devices

#

menuconfig NFC_DEVICES

	bool "NFC devices"

	default n

	---help---

	  You'll have to say Y if your computer contains an NFC device that

	  you want to use under Linux.

	  You can say N here if you don't have any Near Field Communication

	  devices connected to your computer.

if NFC_DEVICES

config PN544_NFC

	tristate "PN544 NFC driver"

	depends on I2C

	select CRC_CCITT

	default n

	---help---

	  Say yes if you want PN544 Near Field Communication driver.

	  This is for i2c connected version. If unsure, say N here.

	  To compile this driver as a module, choose m here. The module will

	  be called pn544.

endif # NFC_DEVICES

#

# Makefile for nfc devices

#

obj-$(CONFIG_PN544_NFC)		+= pn544.o