Binder Driver 3: 打开设备

static int binder_open(struct inode *nodp, struct file *filp)
{
    struct binder_proc *proc;
    struct binder_device *binder_dev;

    proc = kzalloc(sizeof(*proc), GFP_KERNEL);     // 为 当前进程 创建 binder_proc 进行描述
    spin_lock_init(&proc->inner_lock);
    spin_lock_init(&proc->outer_lock);
    get_task_struct(current->group_leader);        // 获取当前进程的 task_struct 
    proc->tsk = current->group_leader;
    INIT_LIST_HEAD(&proc->todo);
    
    if (binder_supported_policy(current->policy)) {
        proc->default_priority.sched_policy = current->policy;
        proc->default_priority.prio = current->normal_prio;
    } else {
        proc->default_priority.sched_policy = SCHED_NORMAL;
        proc->default_priority.prio = NICE_TO_PRIO(0);
    }

    binder_dev = container_of(filp->private_data, struct binder_device,
                  miscdev);
    proc->context = &binder_dev->context;
    binder_alloc_init(&proc->alloc);              // 这是关键，初始化 binder buffer allocator

    binder_stats_created(BINDER_STAT_PROC);       // 维护全局统计信息 binder_stats
    proc->pid = current->group_leader->pid;
    INIT_LIST_HEAD(&proc->delivered_death);
    INIT_LIST_HEAD(&proc->waiting_threads);
    filp->private_data = proc;                    // Driver 的惯用伎俩

    mutex_lock(&binder_procs_lock);                   // 全局锁
    hlist_add_head(&proc->proc_node, &binder_procs);  // 将 当前 binder_proc 加入到 全局的 binder_procs 中
    mutex_unlock(&binder_procs_lock);

    return 0;
}

// proc->alloc 初始化
void binder_alloc_init(struct binder_alloc *alloc)
{
    alloc->tsk = current->group_leader;
    alloc->pid = current->group_leader->pid;
    mutex_init(&alloc->mutex);
    INIT_LIST_HEAD(&alloc->buffers);
}