2011-10-11 1:11:14-优快云博客

本文链接：https://blog.youkuaiyun.com/cstk502/article/details/6868498

本文详细介绍了如何在系统中模拟并实现多个串口的驱动，包括初始化、添加串口实例、以及通过串口进行数据读写操作。重点阐述了在特定场景下，如何根据串口类型和状态调整读写流程，确保数据的正确传输。

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2011-10-11 1:11:14

#define Q_TAILQ_ENTRY(type, qual)                                       \
struct {                                                                \
        qual type *tqe_next;            /* next element */              \
        qual type *qual *tqe_prev;      /* address of previous next element */\
}
#define QTAILQ_ENTRY(type)       Q_TAILQ_ENTRY(struct type,)

字符驱动状态

struct CharDriverState {
    void (*init)(struct CharDriverState *s);
    int (*chr_write)(struct CharDriverState *s, const uint8_t *buf, int len);
    void (*chr_update_read_handler)(struct CharDriverState *s);
    int (*chr_ioctl)(struct CharDriverState *s, int cmd, void *arg);
    IOEventHandler *chr_event;
    IOCanRWHandler *chr_can_read;
    IOReadHandler *chr_read;
    void *handler_opaque;
    void (*chr_send_event)(struct CharDriverState *chr, int event);
    void (*chr_close)(struct CharDriverState *chr);
    void (*chr_accept_input)(struct CharDriverState *chr);
    void *opaque;
    int focus;
    QEMUBH *bh;
    char *label;
    char *filename;
    QTAILQ_ENTRY(CharDriverState) next;
};

void qemu_chr_add_handlers(CharDriverState *s,
                           IOCanRWHandler *fd_can_read,
                           IOReadHandler *fd_read,
                           IOEventHandler *fd_event,
                           void *opaque)
{
    s->chr_can_read = fd_can_read;
    s->chr_read = fd_read;
    s->chr_event = fd_event;
    s->handler_opaque = opaque;
    if (s->chr_update_read_handler)
        s->chr_update_read_handler(s);
}

获取读处理

    if(cs) {
        qemu_chr_add_handlers(cs, tty_can_receive, tty_receive, NULL, s);
    }

    为什么要重置CS的方法


static void goldfish_tty_write(void *opaque, target_phys_addr_t offset, uint32_t value)
{
    struct tty_state *s = (struct tty_state *)opaque;

//printf("goldfish_tty_read %x %x %x\n", offset, value, size);

    switch(offset) {
        case TTY_PUT_CHAR: {
            uint8_t ch = value;
            if(s->cs)
                qemu_chr_write(s->cs, &ch, 1);
        } break;

        case TTY_CMD:
            switch(value) {
                case TTY_CMD_INT_DISABLE:
                    if(s->ready) {
                        if(s->data_count > 0)
                            goldfish_device_set_irq(&s->dev, 0, 0);
                        s->ready = 0;
                    }
                    break;

                    直接调用CS的写方法

                case TTY_CMD_INT_ENABLE:
                    if(!s->ready) {
                        if(s->data_count > 0)
                            goldfish_device_set_irq(&s->dev, 0, 1);
                        s->ready = 1;
                    }
                    break;

                case TTY_CMD_WRITE_BUFFER:
                    if(s->cs) {
                        int len;
                        target_phys_addr_t buf;

buf = s->ptr;
len = s->ptr_len;

                        while (len) {
                            char   temp[64];
                            int    to_write = sizeof(temp);
                            if (to_write > len)
                                to_write = len;

                            cpu_memory_rw_debug(cpu_single_env, buf, temp, to_write, 0);
                            qemu_chr_write(s->cs, temp, to_write);
                            buf += to_write;
                            len -= to_write;
                        }
                        //printf("goldfish_tty_write: got %d bytes from %x\n", s->ptr_len, s->ptr);
                    }
                    break;

                case TTY_CMD_READ_BUFFER:
                    if(s->ptr_len > s->data_count)
                        cpu_abort (cpu_single_env, "goldfish_tty_write: reading more data than available %d %d\n", s->ptr_len, s->data_count);
                    cpu_memory_rw_debug(cpu_single_env,s->ptr, s->data, s->ptr_len,1);
                    //printf("goldfish_tty_write: read %d bytes to %x\n", s->ptr_len, s->ptr);
                    if(s->data_count > s->ptr_len)
                        memmove(s->data, s->data + s->ptr_len, s->data_count - s->ptr_len);
                    s->data_count -= s->ptr_len;
                    if(s->data_count == 0 && s->ready)
                        goldfish_device_set_irq(&s->dev, 0, 0);
                    break;

                default:
                    cpu_abort (cpu_single_env, "goldfish_tty_write: Bad command %x\n", value);
            };
            break;

        case TTY_DATA_PTR:
            s->ptr = value;
            break;

        case TTY_DATA_LEN:
            s->ptr_len = value;
            break;

        default:
            cpu_abort (cpu_single_env, "goldfish_tty_write: Bad offset %x\n", offset);
    }
}

    goldfish_tty_add(serial_hds[0], 0, 0xff002000, 4);
    for(i = 1; i < MAX_SERIAL_PORTS; i++) {
        //printf("android_arm_init serial %d %x\n", i, serial_hds[i]);
        if(serial_hds[i]) {
            goldfish_tty_add(serial_hds[i], i, 0, 0);
        }
    }

    模拟了4个串口