自己实现linux串口驱动
其实driver/tty/serial目录下有很多厂家自己的uart驱动，还有些是spi转串口的驱动。
不过这些都设计到外围硬件，我这里没有外围设备，只是自己模拟来玩的，以后用到硬件时候往里面加就行了，驱动如下：
/* * drivers/tty/serial/sw_uart.c * (C) Copyright 2007-2011 * Reuuimlla Technology Co., Ltd. <www.reuuimllatech.com> * Aaron.Maoye <[email protected]> * * description for this code * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of * the License, or (at your option) any later version. * */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/io.h> #include <linux/irq.h> #include <linux/clk.h> #include <linux/gpio.h> #include <linux/delay.h> #include <linux/ctype.h> #include <linux/slab.h> #include <linux/proc_fs.h> #include <linux/platform_device.h> #include <linux/console.h> #include <linux/tty.h> #include <linux/tty_flip.h> #include <linux/serial_core.h> #include <linux/workqueue.h> #include <linux/serial.h> #include <linux/module.h> #include <linux/ioport.h> #include <linux/init.h> #include <linux/console.h> #include <linux/sysrq.h> #include <linux/delay.h> #include <linux/platform_device.h> #include <linux/tty.h> #include <linux/ratelimit.h> #include <linux/tty_flip.h> #include <linux/serial_reg.h> #include <linux/serial_core.h> #include <linux/serial.h> #include <linux/nmi.h> #include <linux/mutex.h> #include <linux/slab.h> #include <linux/clk.h> #include <linux/timer.h> #include <linux/workqueue.h> #include <linux/dma-mapping.h> #include <asm/io.h> #include <asm/irq.h> #define SW_UART_NR 8 static struct timer_list *timer; struct platform_device *pdev; struct work_struct q_work; struct workqueue_struct *workqueue; volatile static int force_enable_work; //当有硬件数据到来时，要手动调用该函数接收数据并上报 static void sw_uart_handle_rx(unsigned long data) { #if 1 struct uart_port * port; struct tty_struct *tty; unsigned char ch = 0; int i; int flag; char *send_buff = "i am sclu, this is from serial rx"; flag = TTY_NORMAL; printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); port = (struct uart_port *)data; if (!port) return; if (!port->state) return; tty = port->state->port.tty; //tty->flags |= TTY_HW_COOK_IN; //tty = port->info->tty; if (!tty) return; // for (i = 0; i < strlen(send_buff) + 1; i++) { //用tty_insert_flip_char函数也可以 // ch = send_buff[i]; // uart_insert_char(port, 0, 0, ch, flag); // } tty_insert_flip_string(tty, send_buff, strlen(send_buff) + 1); // uart_insert_char(port, 0, 0, '\n', flag); // uart_insert_char(port, 0, 0, '\t', 0); tty_flip_buffer_push(tty); #endif timer->expires = jiffies + 3 * HZ; add_timer(timer); } static void sw_uart_stop_tx(struct uart_port *port) { //del_timer(timer); printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } //上层用户空间写的数据最终调用该函数完成发送 static void sw_uart_start_tx(struct uart_port *port) { struct circ_buf *xmit = &port->state->xmit; // printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); //开始发送数据 if(!force_enable_work || uart_circ_empty(xmit) || uart_tx_stopped(port)) queue_work(workqueue, &q_work); } static unsigned int sw_uart_tx_empty(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); //当硬件fifo中的数据发送完成后，要返回TIOCSER_TEMI，否则上层一直写等待，如echo数据一直没有返回 return TIOCSER_TEMT; } static void sw_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static unsigned int sw_uart_get_mctrl(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); return 0; } static void sw_uart_stop_rx(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static void sw_uart_enable_ms(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static void sw_uart_break_ctl(struct uart_port *port, int break_state) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static int sw_uart_startup(struct uart_port *port) { /* this is the first time this port is opened */ /* do any hardware initialization needed here */ /* create our timer and submit it */ force_enable_work = 0; if (!timer) { timer = kmalloc(sizeof(*timer), GFP_KERNEL); if (!timer) return -ENOMEM; } setup_timer(timer, sw_uart_handle_rx, (unsigned long)port); timer->expires = jiffies + HZ * 3; #if 0 timer->data = (unsigned long)port; timer->expires = jiffies + DELAY_TIME; timer->function = tiny_timer; #endif add_timer(timer); printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); return 0; } static void sw_uart_shutdown(struct uart_port *port) { /* The port is being closed by the last user. */ /* Do any hardware specific stuff here */ /* shut down our timer */ printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); force_enable_work = 1; cancel_work_sync(&q_work); } static void sw_uart_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static const char *sw_uart_type(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); return "SW"; } static void sw_uart_release_port(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static int sw_uart_request_port(struct uart_port *port) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); return 0; } static void sw_uart_config_port(struct uart_port *port, int flags) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static int sw_uart_verify_port(struct uart_port *port, struct serial_struct *ser) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); return 0; } static void sw_uart_pm(struct uart_port *port, unsigned int state, unsigned int oldstate) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); } static struct uart_driver sw_uart_driver; static struct uart_ops sw_uart_ops = { #if 1 .tx_empty = sw_uart_tx_empty, .set_mctrl = sw_uart_set_mctrl, .get_mctrl = sw_uart_get_mctrl, .stop_tx = sw_uart_stop_tx, .enable_ms = sw_uart_enable_ms, .break_ctl = sw_uart_break_ctl, .set_termios = sw_uart_set_termios, .type = sw_uart_type, .release_port = sw_uart_release_port, .request_port = sw_uart_request_port, .config_port = sw_uart_config_port, .verify_port = sw_uart_verify_port, .pm = sw_uart_pm, #endif .startup = sw_uart_startup, .start_tx = sw_uart_start_tx, .stop_rx = sw_uart_stop_rx, .shutdown = sw_uart_shutdown, }; static struct uart_port tiny_port = { .ops = &sw_uart_ops, .type = PORT_8250, .fifosize = 64, .flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF, }; #ifdef CONFIG_CONSOLE_POLL static void sw_console_write(struct console *co, const char *s, unsigned int count) { } static int __init sw_console_setup(struct console *co, char *options) { struct uart_port *port; int baud = 115200; int bits = 8; int parity = 'n'; int flow = 'n'; port = &tiny_port; if (options) uart_parse_options(options, &baud, &parity, &bits, &flow); return uart_set_options(port, co, baud, parity, bits, flow); } #endif static void tx_work(struct work_struct *work) { #if 1 struct uart_port *port = &tiny_port; struct circ_buf *xmit = &port->state->xmit; int count; // printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); if (port->x_char) { printk("x_char %2x", port->x_char); port->icount.tx++; port->x_char = 0; return; } if (uart_circ_empty(xmit) || uart_tx_stopped(port)) { return; } count = port->fifosize / 2; // printk("sclu %s, count = %d\n", __func__, count); //发送数据 // serial_out(&sw_uport->port, xmit->buf[xmit->tail], SW_UART_THR); printk("get data:\n"); do { printk("%c", xmit->buf[xmit->tail]); xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); port->icount.tx++; if (uart_circ_empty(xmit)) { break; } } while (--count > 0); printk("\n"); if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) { // spin_unlock(&port->lock); uart_write_wakeup(port); // spin_lock(&port->lock); } if (uart_circ_empty(xmit)) sw_uart_stop_tx(port); #endif } #ifdef CONFIG_CONSOLE_POLL static struct console sw_console = { .name = "ttyVirtual", .write = sw_console_write, .device = uart_console_device, .setup = sw_console_setup, .flags = CON_PRINTBUFFER | CON_ANYTIME, .index = -1, .data = &sw_uart_driver, }; #define SERIAL_CONSOLE &sw_console #else #define SERIAL_CONSOLE NULL #endif static struct uart_driver sw_uart_driver = { .owner = THIS_MODULE, .driver_name = "Virtual_serial", .dev_name = "ttyVirtual", .nr = SW_UART_NR, .cons = SERIAL_CONSOLE, }; static int __devinit sw_uart_probe(struct platform_device *pdev) { printk("%s, %d, %s\n", __FILE__, __LINE__, __func__); workqueue = create_singlethread_workqueue("ttyVirtual_work"); INIT_WORK(&q_work, tx_work); return uart_add_one_port(&sw_uart_driver, &tiny_port); } static int __devexit sw_uart_remove(struct platform_device *pdev) { return 0; } #define SERIAL_SW_PM_OPS NULL static struct platform_driver sw_uport_platform_driver = { .probe = sw_uart_probe, .remove = __devexit_p(sw_uart_remove), .driver.name = "ttyVirtual", .driver.pm = SERIAL_SW_PM_OPS, .driver.owner = THIS_MODULE, }; static int __init sw_uart_init(void) { int ret; printk("serial driver initializied\n"); ret = uart_register_driver(&sw_uart_driver); if (unlikely(ret)) { printk("serial driver initializied err\n"); return ret; } pdev = platform_device_register_simple("ttyVirtual", 0, NULL, 0); return platform_driver_register(&sw_uport_platform_driver); } static void __exit sw_uart_exit(void) { if (timer) { del_timer(timer); timer = NULL; } if (workqueue) { flush_workqueue(workqueue); destroy_workqueue(workqueue); workqueue = NULL; } printk("driver exit\n"); uart_remove_one_port(&sw_uart_driver, &tiny_port); platform_driver_unregister(&sw_uport_platform_driver); if (pdev) platform_device_unregister(pdev); uart_unregister_driver(&sw_uart_driver); } module_init(sw_uart_init); module_exit(sw_uart_exit); MODULE_AUTHOR("Aaron<[email protected]>"); MODULE_DESCRIPTION("Driver for SW serial device"); MODULE_LICENSE("GPL");
上层测试代码如下：
#include <termios.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <jni.h>
#include <assert.h>
#include <errno.h>
#include <sys/epoll.h>
#include <pthread.h>
#include <sys/socket.h>
#include <utils/Log.h>
#include <stdlib.h>
static int epoll_register(int epoll_fd, int fd) {
struct epoll_event ev;
int ret, flags;
/* important: make the fd non-blocking */
flags = fcntl(fd, F_GETFL);
fcntl(fd, F_SETFL, flags | O_NONBLOCK);
//fcntl(fd, F_SETOWN, getpid()); //sclu add
ev.events = EPOLLIN;
ev.data.fd = fd;
do {
ret = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, fd, &ev);
} while (ret < 0 && errno == EINTR);
return ret;
}
int main(int argc, char **argv)
{
struct termios uart_termios;
int baudrate = atoi(argv[2]);
int epoll_fd = epoll_create(1);
int ret, err;
char read_buf[1024];
int fd = open(argv[1], O_RDWR|O_NOCTTY|O_NDELAY);
if(fd < 0) {
LOGE("open %s failure, err = %s\n", argv[1], strerror(errno));
return fd;
}
fcntl(fd, F_SETFL, 0);
tcflush(fd, TCIOFLUSH);
if ((err = tcgetattr(fd, &uart_termios)) != 0) {
LOGE("tcgetattr %s, err = %s\n", argv[1], strerror(errno));
close(fd);
return err;
}
uart_termios.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL|IXON);
uart_termios.c_oflag &= ~OPOST;
uart_termios.c_lflag &= ~(ECHO|ECHONL|ICANON|ISIG|IEXTEN);
uart_termios.c_cflag &= ~(CSIZE|PARENB);
uart_termios.c_cflag |= CS8;
uart_termios.c_cflag &= ~CRTSCTS;//no flow control
tcsetattr(fd, TCSANOW, &uart_termios);
tcflush(fd, TCIOFLUSH);
tcsetattr(fd, TCSANOW, &uart_termios);
tcflush(fd, TCIOFLUSH);
if (cfsetispeed(&uart_termios, baudrate)) {
LOGE("cfsetispeed, err = %s\n", strerror(errno));
close(fd);
return fd;
}
if (cfsetospeed(&uart_termios, baudrate)) {
LOGE("cfsetospeed err = %s\n", strerror(errno));
close(fd);
return fd;
}
tcsetattr (fd, TCSANOW, &uart_termios);
epoll_register(epoll_fd, fd);
ret = write(fd, "$$$$", 4);
LOGE("ret = %d", ret);
if ((ret = read(fd, read_buf, sizeof(read_buf))) > 0) {
int i;
for (i = 0; i < ret; i++) {
LOGE("read:%c", read_buf[i]);
}
LOGE("\n");
}
for (;;) {
struct epoll_event events[1];
int ne, nevents, ret, size;
LOGE("poll start");
nevents = epoll_wait(epoll_fd, events, 1, -1);
LOGE("poll get data");
if (nevents < 0) {
if (errno != EINTR)
LOGE("epoll_wait() unexpected error: %s", strerror(errno));
continue;
}
for (ne = 0; ne < nevents; ne++) {
if ((events[ne].events & (EPOLLERR | EPOLLHUP)) != 0) {
LOGE("EPOLLERR or EPOLLHUP after epoll_wait() !?\n");
return -1;
}
if ((events[ne].events & EPOLLIN) != 0) {
int event_fd = events[ne].data.fd;
int i;
if (event_fd == fd) {
ret = read(fd, read_buf, sizeof(read_buf));
if (ret) {
LOGE("data:%s", read_buf);
char *p = "this is from userspace!";
write(fd, p, strlen(p) + 1);
}
}
}
}
}
return 0;
}
调试中遇到的问题有sw_uart_tx_empty函数中不能返回0，要返回TIOCSER_TEMT，否则上层一直写等待
还有就是打开节点时候要设置串口信息，入上面测试代码所示，刚开始自己用 cat /dev/ttyVirtual来看信息，发现底层发送上来的数据到了tty核心层后，原样的发送回去了，虽然上层一样可以接收到，但不是想要的结果。
还有,linux系用已经为我们写好了serial_core.c架构，我们的串口设备只学要按照其格式实现相应的函数即可，不过我们也可以自己实现一个,只要实现相应的tty_operations结构体函数即可，然后把它注册到tty核心层中，以后自己的串口驱动如果不需要linux默认的serial_core,注册时候指定自己的tty driver即可。
代码如下，功能是往tty driver写入数据，然后原样发送回来：
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/tty.h>
#include <linux/fs.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/ioport.h>
#include <linux/serial_reg.h>
#include <linux/slab.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/tty.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("sclu");
#define TTY_LAN_MINORS_NUM 1
#define TTY_LAN_MAJOR 240
static int open_count = 0;
static struct tty_driver *tty_lan_driver;
static struct tty_struct *tty_lan_struct;
static int tty_lan_open(struct tty_struct *tty, struct file *filp);
static void tty_lan_close(struct tty_struct *tty, struct file *filp);
static int tty_lan_write(struct tty_struct *tty, const unsigned char *buffer, int count);
static int tty_lan_write_room(struct tty_struct *tty);
static void tty_lan_set_termios(struct tty_struct *tty, struct ktermios * old);
static int tty_lan_put_char(struct tty_struct *tty, unsigned char ch);
static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
static struct tty_operations tty_lan_ops = {
.open = tty_lan_open,
.close = tty_lan_close,
.write = tty_lan_write,
.put_char = tty_lan_put_char,
.write_room = tty_lan_write_room,
.set_termios = tty_lan_set_termios,
.wait_until_sent = uart_wait_until_sent,
};
static int __init tty_lan_init(void)
{
int i;
int retval;
tty_lan_driver = alloc_tty_driver(TTY_LAN_MINORS_NUM);
if(!tty_lan_driver)
return -ENOMEM;
tty_lan_driver->owner = THIS_MODULE;
tty_lan_driver->driver_name = "tty_sclu";
tty_lan_driver->name = "ttty_sclu";
tty_lan_driver->major = TTY_LAN_MAJOR,
tty_lan_driver->minor_start = 0;
tty_lan_driver->type = TTY_DRIVER_TYPE_SERIAL;
tty_lan_driver->subtype = SERIAL_TYPE_NORMAL;
//TTY_DRIVER_DYNAMIC_DEV标志表示手动注册device设备，在tty_io.c中会判断，如果没有该标志，会调用tty_register_device,
//后续就不用再次注册device设备了
tty_lan_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
tty_lan_driver->init_termios = tty_std_termios;
tty_lan_driver->init_termios.c_cflag = B115200 | CS8 | CREAD | HUPCL | CLOCAL;
tty_set_operations(tty_lan_driver, &tty_lan_ops);
retval = tty_register_driver(tty_lan_driver);
if(retval){
printk(KERN_ERR"Failed to register tty_lan_driver!\n");
put_tty_driver(tty_lan_driver);
return retval;
}
tty_register_device(tty_lan_driver, 0, NULL);
return 0;
}
static int tty_lan_open(struct tty_struct *tty, struct file *filp)
{
if(open_count == 0){
printk("Open OK!\n");
}
tty_lan_struct = kmalloc(sizeof(struct tty_struct), GFP_KERNEL);
tty->low_latency = 1;
tty_lan_struct = tty;
return 0;
}
static void tty_lan_close(struct tty_struct *tty, struct file *filp)
{
printk("ClOSE OK!\n");
kfree(tty_lan_struct);
return;
}
static int tty_lan_write(struct tty_struct *tty, const unsigned char *buffer, int count)
{
int retval = count;
tty = tty_lan_struct;
printk(KERN_DEBUG "%s - \n", __FUNCTION__);
printk("count :%d\n", count);
printk("user write: %s ", buffer);
printk("\n");
tty_insert_flip_string(tty, buffer, count);
tty_flip_buffer_push(tty);
return retval;
}
static int tty_lan_put_char(struct tty_struct *tty, unsigned char ch)
{
printk("%c", ch);
return 0;
}
static int tty_lan_write_room(struct tty_struct *tty)
{
int room;
room = 255;
return room;
}
static void tty_lan_set_termios(struct tty_struct *tty, struct ktermios *old)
{
tty = tty_lan_struct;
if(tty->termios->c_cflag == old->c_cflag){
printk("Nothing to change!\n");
return ;
}
printk("There is something to Change............\n");
return ;
}
static void uart_wait_until_sent(struct tty_struct *tty, int timeout)
{
struct uart_state *state = tty->driver_data;
struct uart_port *port = state->uart_port;
printk("%s, %d\n", __func__, __LINE__);
}
static void __exit tty_lan_exit(void)
{
int i;
tty_unregister_device(tty_lan_driver, 0);
tty_unregister_driver(tty_lan_driver);
}
module_init(tty_lan_init);