From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/nfc/nfc-pn544.txt | 114 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) create mode 100644 Documentation/nfc/nfc-pn544.txt (limited to 'Documentation/nfc') diff --git a/Documentation/nfc/nfc-pn544.txt b/Documentation/nfc/nfc-pn544.txt new file mode 100644 index 00000000..2fcac9f5 --- /dev/null +++ b/Documentation/nfc/nfc-pn544.txt @@ -0,0 +1,114 @@ +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, +}; -- cgit v1.2.3