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author | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-06-27 16:31:35 -0300 |
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committer | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-07-15 11:03:03 -0300 |
commit | 65388dad1bbb51a4eb6cc91b9fa865b57646fb67 (patch) | |
tree | 1e9671522c2576a14d6a14df95874e1449fc422d /Documentation/driver-api/serial/serial-iso7816.rst | |
parent | c92992fc609fe99d926855eb1945f38ef4ad8e6c (diff) |
docs: serial: move it to the driver-api
The contents of this directory is mostly driver-api stuff.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'Documentation/driver-api/serial/serial-iso7816.rst')
-rw-r--r-- | Documentation/driver-api/serial/serial-iso7816.rst | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/Documentation/driver-api/serial/serial-iso7816.rst b/Documentation/driver-api/serial/serial-iso7816.rst new file mode 100644 index 000000000000..d990143de0c6 --- /dev/null +++ b/Documentation/driver-api/serial/serial-iso7816.rst @@ -0,0 +1,90 @@ +============================= +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 |