smart210的PWM驱动程序pwm->pwm_id 值的问题

struct pwm_device *pwm_request(int pwm_id, const char *label)  //(0,"pwm")
{
    struct pwm_device *pwm;
    int found = 0;

    mutex_lock(&pwm_lock);
                                              
    list_for_each_entry(pwm, &pwm_list, list)
        {
        if (pwm->pwm_id == pwm_id)      //pwm->pwm_id 的值是哪里来的？哪里初始化或者赋值的？
                {
            found = 1;
            break;
        }
    }

    if (found)
        {
        if (pwm->use_count == 0)
                {
            pwm->use_count = 1;
            pwm->label = label; //"pwm"  (0,"pwm")
        }
                else
            pwm = ERR_PTR(-EBUSY);
    }
        else
        pwm = ERR_PTR(-ENOENT);

    mutex_unlock(&pwm_lock);
    return pwm;
}

其中 pwm->pwm_id 的值是哪里来的？哪里初始化或者赋值的？

建议仔细的看一下 s3c_pwm_probe，也可以加些打印来帮助分析