0001 =============================
0002 ISO7816 Serial Communications
0003 =============================
0004
0005 1. Introduction
0006 ===============
0007
0008 ISO/IEC7816 is a series of standards specifying integrated circuit cards (ICC)
0009 also known as smart cards.
0010
0011 2. Hardware-related considerations
0012 ==================================
0013
0014 Some CPUs/UARTs (e.g., Microchip AT91) contain a built-in mode capable of
0015 handling communication with a smart card.
0016
0017 For these microcontrollers, the Linux driver should be made capable of
0018 working in both modes, and proper ioctls (see later) should be made
0019 available at user-level to allow switching from one mode to the other, and
0020 vice versa.
0021
0022 3. Data Structures Already Available in the Kernel
0023 ==================================================
0024
0025 The Linux kernel provides the serial_iso7816 structure (see [1]) to handle
0026 ISO7816 communications. This data structure is used to set and configure
0027 ISO7816 parameters in ioctls.
0028
0029 Any driver for devices capable of working both as RS232 and ISO7816 should
0030 implement the iso7816_config callback in the uart_port structure. The
0031 serial_core calls iso7816_config to do the device specific part in response
0032 to TIOCGISO7816 and TIOCSISO7816 ioctls (see below). The iso7816_config
0033 callback receives a pointer to struct serial_iso7816.
0034
0035 4. Usage from user-level
0036 ========================
0037
0038 From user-level, ISO7816 configuration can be get/set using the previous
0039 ioctls. For instance, to set ISO7816 you can use the following code::
0040
0041 #include <linux/serial.h>
0042
0043 /* Include definition for ISO7816 ioctls: TIOCSISO7816 and TIOCGISO7816 */
0044 #include <sys/ioctl.h>
0045
0046 /* Open your specific device (e.g., /dev/mydevice): */
0047 int fd = open ("/dev/mydevice", O_RDWR);
0048 if (fd < 0) {
0049 /* Error handling. See errno. */
0050 }
0051
0052 struct serial_iso7816 iso7816conf;
0053
0054 /* Reserved fields as to be zeroed */
0055 memset(&iso7816conf, 0, sizeof(iso7816conf));
0056
0057 /* Enable ISO7816 mode: */
0058 iso7816conf.flags |= SER_ISO7816_ENABLED;
0059
0060 /* Select the protocol: */
0061 /* T=0 */
0062 iso7816conf.flags |= SER_ISO7816_T(0);
0063 /* or T=1 */
0064 iso7816conf.flags |= SER_ISO7816_T(1);
0065
0066 /* Set the guard time: */
0067 iso7816conf.tg = 2;
0068
0069 /* Set the clock frequency*/
0070 iso7816conf.clk = 3571200;
0071
0072 /* Set transmission factors: */
0073 iso7816conf.sc_fi = 372;
0074 iso7816conf.sc_di = 1;
0075
0076 if (ioctl(fd_usart, TIOCSISO7816, &iso7816conf) < 0) {
0077 /* Error handling. See errno. */
0078 }
0079
0080 /* Use read() and write() syscalls here... */
0081
0082 /* Close the device when finished: */
0083 if (close (fd) < 0) {
0084 /* Error handling. See errno. */
0085 }
0086
0087 5. References
0088 =============
0089
0090 [1] include/uapi/linux/serial.h
