With the transition of modern industrial society to the information society, information will play an increasingly important role and become a success factor in modern economic life. As a card type in the card-based application system, the IC card uses an integrated circuit (IC) installed in the card to record and transmit information; it has large storage capacity, good data confidentiality, strong anti-interference ability, and reliable storage. It has the advantages of simple reading and writing equipment, fast operation speed and strong offline working ability, and its application range is extremely wide.
Based on the application of public telephone IC card, we have developed multimedia information terminal products. On the basis of the traditional public IC card telephone function, we have added various multimedia functions such as Internet access, mail, electronic payment, information browsing, etc., and unified use of public telephone IC cards. toll. Currently designed IC card readers and driver software have been applied to our multimedia terminal products.
1 Introduction to device driver module under embedded Linux
Linux systems divide devices into three types: character devices, block devices, and network interfaces. The three types of devices are defined as follows:
Character devices: Character devices are devices that can be accessed like byte streams (such as files), such as character terminals (/dev/con s01e) and serial ports (/dev/ttys0) and similar devices. The character device corresponds to a node in the file system, and the user accesses and controls the device through the file node.
Block devices: Block devices can be accessed through file system nodes just like character devices. Linux allows applications to read and write block devices like character devices.
Network interface: Any network device must go through a network interface, a device that can exchange data with other hosts. Usually the interface is a hardware device, but it could also be a software-only device, such as a loopback (100pback) interface. The way Linux accesses the network interface is to assign a unique name.
Module is a major innovation of the Linux kernel. Its regular name should be Loadable Kernel Module, and modules can be installed. The installable module implements the scalability of the Linux operating system. The module runs in a kernel space environment, and its program run function library is defined in kernel space, not in the user function library space. The most convenient part of the Linux module is loadable and unloadable. The Linux operating system provides system calls in smod and rmmod to load and unload modules developed by you at any time.
According to the Linux device classification, the device driver module can be roughly classified into a character module (char module), a block module (block module), and a network module (network module).
2 IC card device contact hardware circuit introduction
The IC card hardware contact interface and signal are as follows.
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Among the above contacts, the VPP programming voltage contact is used by the manufacturer when programming the card, and the user card is not applied when reading or writing. So to be precise, only five contacts are connected to the five control signals from the external main controller. Subsequent operations after device reset may include card address setting operations, read and write operations, and erase operations. There are strict signal control timings for the various operations of the above cards. For details, refer to the DATASHEET of various application cards. As a card type in the card base application system, the IC card uses an integrated circuit (IC) installed in the card to record and transfer information, so the IC card has a specific storage bitmap. The specific storage bitmap has different bitmap definitions for different application areas and different standards. For details, please refer to the DATASHEET data of the application card. In the development process of the driver, only after fully understanding the definition of these bitmaps, the read data can be decoded according to the bitmap definition protocol to obtain various data that is ultimately needed by the user.
3 IC card reading circuit introduction
We use the MPC823E as the main processor. Because the IC contact operating voltage is 5V, and the main controller's operating voltage is 3.3V, the intermediate level conversion drive circuit is designed in the card reader, and the driving ability of the control signal is increased. In order to detect the card operation in real time, a switch circuit is arranged in the card circuit, and the control line of the main controller is connected to detect whether the card is inserted.
4 IC card device driver module implementation details
The following takes the IC card common to the public telephones we use as an example, and the entire IC card device driving module is explained by the implemented code.
(1) Determination of data structure
Edit the header file ICDATA.H to determine the common data structure applied in the driver module program. The ultimate goal of the driver module is to read and write card data processing, so a well-organized data structure is a must. A data structure can be defined to implement the storage area of ​​the card data, the data address index, the control flag, and the like, such as: .jpg)
Thus, in the driver module, only struct ICDATA iccdata is required; one statement can define all the card processing data structure definitions; and ic_fops defines the device operation mapping function structure. From this data structure, we implemented the functions of opening, reading, writing and monitoring of IC card devices.
(2) hardware interface control line control subfunction
These functions are used to control signals such as card reset and clock. .jpg)
The above is one of the hardware control interface operation functions of the hardware system platform developed by us, which is used to control the reset signal of the IC card to be set to 1. The internal operation methods of the functions are different for different hardware platforms. Other similar operational functions are: .jpg)
(3) Implementation of module initialization function .jpg)
The module initialization function is an indispensable processing function in the module development process, which is used to implement device initialization, interrupt initialization and processing, and device registration. In the above function, the initidata (&icdata) is first applied to initialize the card data, and then the queue data is defined. The binding of the interrupt handler, the interrupt request, and the interrupt initialization are performed. Finally, the application for the IC card character device was realized. The device name is IC.
(4) Interrupt processing
The module uses the timer interrupt of the MPC823E to detect the status of the card when each timer interrupt occurs. If the card is detected, the card reading operation is performed; if the card unplugging operation is detected, the card data is cleared and the card status data is updated.
The interrupt processing in the program uses the timer_task task queue to implement subsequent processing of the interrupt. Its handler is time r_do_tasklet. The M8xx timer_setup() function first initializes and parameterizes the MPC823E timer. Then, the application CPm_in stall_handler rCPMVEC TIMER4, m8xx_timerinterrupt, (void*)0); implements the binding of the resource application of the interrupt processing and the interrupt processing function m 8 x x_timer_interrupt().
Use the statement in the interrupt handler:
Queue_task(&timer_task,&tq_immediate);
Mark_bh(IMMEDIATE_BH);
The task queue timer_task is added to the task queue processing of the kernel tq_immediate. The kernel automatically calls the timer_task routine handler timer_do_taskletO at the appropriate time for subsequent processing of the interrupt.
In the time r dO_ta sklet() handler, there is a statement wake up interruptible(&icde v.writeq) that corresponds to D011_wait(flip,&icdev.writeq,wait) in the ic_poll function. When the interrupt occurs, it will wait for the time queue icdev. Writeq is activated; the poll_wait function monitors this queue. Once activated, the user can be passed to the card operation information, and the read function can be called immediately in the user application software to perform the card reading operation. This enables real-time operation monitoring of the card.
(5) Implementation of module logout function .jpg)
This function is also one of the indispensable functions in module driver development. It is used to release resources when the module is unloaded and to unregister this module. As shown in the above function, the interrupt is stopped first, the interrupt resource is released, and the character device is deregistered.
(6) Sub-functions such as device read, write, and monitor
It is used to realize the operation of the card, mainly by implementing various operation timings of the card. That is, the four operation functions defined in the ic_fop s structure: icopen is used to open the card device, and some data initialization operations are performed; icread() is used to read the card data during the card operation; icwrite() is used to write the card. ;icpoll() is used to implement real-time monitoring of the card.
In summary, the basic implementation principle of the card driver module is: applying for interrupt resources, when a card insertion operation occurs, causing an interrupt and performing a card reading operation. Interrupts can also be triggered during card extraction and data processing is performed at the same time. At the same time, the poll() function interface is provided, and the user can use this function to monitor the device, so that the card data is updated immediately when the card operation occurs.
6 driver module statically compiled into the kernel
1 Copy the module driver source file into the /drivers/char/ directory;
2 modify the /drivers/char/Makefile file, add obj-$(CONFIG_MYMODULE)+=ic.o
3 Add config CONFIG_MYMODULE bool "IC" CONFIG_MYMODULE in the /drivers/char/config.in file
4 Enter the compiled kernel directory and execute make menuconfig.
You can see the IC options in the character devices directory. Select and then execute the compile command to compile the kernel or just compile the module:
Make mrproper
Make menuconfig
Make CROSS_COMPILE=ppc_8xx-gcc
Make modules CROSS_COMPILE=ppc_8xx-gcc
You can just compile the kernel. Ic.o is visible in the source file directory.
7 Summary
The development of the driver module of the IC card device is realized by the basic character device. The development of the kernel driver module is in direct contact with the hardware. The internal processing methods vary from hardware to hardware. For kernel module development, the most effective learning path and the best learning documentation is the kernel source code for Linux. At the same time, joining some Linux mail development teams will also benefit.
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