84 lines
2.4 KiB
Plaintext
84 lines
2.4 KiB
Plaintext
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ISO7816 SERIAL COMMUNICATIONS
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1. INTRODUCTION
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ISO/IEC7816 is a series of standards specifying integrated circuit cards (ICC)
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also known as smart cards.
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2. HARDWARE-RELATED CONSIDERATIONS
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Some CPUs/UARTs (e.g., Microchip AT91) contain a built-in mode capable of
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handling communication with a smart card.
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For these microcontrollers, the Linux driver should be made capable of
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working in both modes, and proper ioctls (see later) should be made
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available at user-level to allow switching from one mode to the other, and
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vice versa.
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3. DATA STRUCTURES ALREADY AVAILABLE IN THE KERNEL
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The Linux kernel provides the serial_iso7816 structure (see [1]) to handle
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ISO7816 communications. This data structure is used to set and configure
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ISO7816 parameters in ioctls.
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Any driver for devices capable of working both as RS232 and ISO7816 should
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implement the iso7816_config callback in the uart_port structure. The
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serial_core calls iso7816_config to do the device specific part in response
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to TIOCGISO7816 and TIOCSISO7816 ioctls (see below). The iso7816_config
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callback receives a pointer to struct serial_iso7816.
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4. USAGE FROM USER-LEVEL
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From user-level, ISO7816 configuration can be get/set using the previous
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ioctls. For instance, to set ISO7816 you can use the following code:
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#include <linux/serial.h>
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/* Include definition for ISO7816 ioctls: TIOCSISO7816 and TIOCGISO7816 */
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#include <sys/ioctl.h>
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/* Open your specific device (e.g., /dev/mydevice): */
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int fd = open ("/dev/mydevice", O_RDWR);
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if (fd < 0) {
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/* Error handling. See errno. */
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}
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struct serial_iso7816 iso7816conf;
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/* Reserved fields as to be zeroed */
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memset(&iso7816conf, 0, sizeof(iso7816conf));
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/* Enable ISO7816 mode: */
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iso7816conf.flags |= SER_ISO7816_ENABLED;
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/* Select the protocol: */
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/* T=0 */
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iso7816conf.flags |= SER_ISO7816_T(0);
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/* or T=1 */
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iso7816conf.flags |= SER_ISO7816_T(1);
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/* Set the guard time: */
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iso7816conf.tg = 2;
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/* Set the clock frequency*/
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iso7816conf.clk = 3571200;
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/* Set transmission factors: */
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iso7816conf.sc_fi = 372;
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iso7816conf.sc_di = 1;
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if (ioctl(fd_usart, TIOCSISO7816, &iso7816conf) < 0) {
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/* Error handling. See errno. */
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}
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/* Use read() and write() syscalls here... */
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/* Close the device when finished: */
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if (close (fd) < 0) {
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/* Error handling. See errno. */
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}
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5. REFERENCES
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[1] include/uapi/linux/serial.h
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