From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 7 Apr 2024 20:49:45 +0200
Subject: Adding upstream version 6.1.76.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 Documentation/driver-api/serial/serial-iso7816.rst | 90 ++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 Documentation/driver-api/serial/serial-iso7816.rst

(limited to 'Documentation/driver-api/serial/serial-iso7816.rst')

diff --git a/Documentation/driver-api/serial/serial-iso7816.rst b/Documentation/driver-api/serial/serial-iso7816.rst
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+=============================
+ISO7816 Serial Communications
+=============================
+
+1. Introduction
+===============
+
+  ISO/IEC7816 is a series of standards specifying integrated circuit cards (ICC)
+  also known as smart cards.
+
+2. Hardware-related considerations
+==================================
+
+  Some CPUs/UARTs (e.g., Microchip AT91) contain a built-in mode capable of
+  handling communication with a smart card.
+
+  For these microcontrollers, the Linux driver should be made capable of
+  working in both modes, and proper ioctls (see later) should be made
+  available at user-level to allow switching from one mode to the other, and
+  vice versa.
+
+3. Data Structures Already Available in the Kernel
+==================================================
+
+  The Linux kernel provides the serial_iso7816 structure (see [1]) to handle
+  ISO7816 communications. This data structure is used to set and configure
+  ISO7816 parameters in ioctls.
+
+  Any driver for devices capable of working both as RS232 and ISO7816 should
+  implement the iso7816_config callback in the uart_port structure. The
+  serial_core calls iso7816_config to do the device specific part in response
+  to TIOCGISO7816 and TIOCSISO7816 ioctls (see below). The iso7816_config
+  callback receives a pointer to struct serial_iso7816.
+
+4. Usage from user-level
+========================
+
+  From user-level, ISO7816 configuration can be get/set using the previous
+  ioctls. For instance, to set ISO7816 you can use the following code::
+
+	#include <linux/serial.h>
+
+	/* Include definition for ISO7816 ioctls: TIOCSISO7816 and TIOCGISO7816 */
+	#include <sys/ioctl.h>
+
+	/* Open your specific device (e.g., /dev/mydevice): */
+	int fd = open ("/dev/mydevice", O_RDWR);
+	if (fd < 0) {
+		/* Error handling. See errno. */
+	}
+
+	struct serial_iso7816 iso7816conf;
+
+	/* Reserved fields as to be zeroed */
+	memset(&iso7816conf, 0, sizeof(iso7816conf));
+
+	/* Enable ISO7816 mode: */
+	iso7816conf.flags |= SER_ISO7816_ENABLED;
+
+	/* Select the protocol: */
+	/* T=0 */
+	iso7816conf.flags |= SER_ISO7816_T(0);
+	/* or T=1 */
+	iso7816conf.flags |= SER_ISO7816_T(1);
+
+	/* Set the guard time: */
+	iso7816conf.tg = 2;
+
+	/* Set the clock frequency*/
+	iso7816conf.clk = 3571200;
+
+	/* Set transmission factors: */
+	iso7816conf.sc_fi = 372;
+	iso7816conf.sc_di = 1;
+
+	if (ioctl(fd_usart, TIOCSISO7816, &iso7816conf) < 0) {
+		/* Error handling. See errno. */
+	}
+
+	/* Use read() and write() syscalls here... */
+
+	/* Close the device when finished: */
+	if (close (fd) < 0) {
+		/* Error handling. See errno. */
+	}
+
+5. References
+=============
+
+ [1]    include/uapi/linux/serial.h
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