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authorMatti J. Aaltonen <matti.j.aaltonen@nokia.com>2011-01-12 17:00:47 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-01-13 08:03:19 -0800
commit0329326e85aaa30fb8d427828c718d565c287385 (patch)
treeab6d9c1e9c6a56ebca273b9d36d76a4a3eb60b23 /Documentation/nfc
parent6164281ab7a4d3bd42588d6b25984e960a2e032f (diff)
downloadlinux-linaro-stable-0329326e85aaa30fb8d427828c718d565c287385.tar.gz
NFC: Driver for NXP Semiconductors PN544 NFC chip.
Creates a new "Near Field Communication" subsystem in drivers/nfc. http://en.wikipedia.org/wiki/Near_Field_Communication is useful ;) This is a driver for the pn544 NFC device. The driver transfers ETSI messages between the device and the user space. Signed-off-by: Matti J. Aaltonen <matti.j.aaltonen@nokia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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+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,
+};