android binder（三）binder.c函数分析

一、binder_call

int binder_call(struct binder_state *bs,struct binder_io *msg, struct binder_io *reply,uint32_t target, uint32_t code);

实现远程调用RPC，既然是远程函数调用，那么就有如下要素：

• 向谁发送数据：target

• 调用哪个函数：code

• 提供什么参数：msg

• 返回值：reply

如何使用？

• 构造参数：存放在buf中，用binder_io结构体描述

      struct binder_io{char *data;            /* pointer to read/write from */binder_size_t *offs;   /* array of offsets */size_t data_avail;     /* bytes available in data buffer */size_t offs_avail;     /* entries available in offsets array */char *data0;           /* start of data buffer */binder_size_t *offs0;  /* start of offsets buffer */uint32_t flags;uint32_t unused;};

• 数据格式转换，将binder_io数据转换成驱动程序要求的binder_write_read数据
• 调用ioctl发送数据--ioctl(bs->fd, BINDER_WRITE_READ, &bwr);

struct binder_write_read {binder_size_t write_size;binder_size_t write_consumed;binder_uintptr_t write_buffer;
/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */binder_size_t read_size;binder_size_t read_consumed;binder_uintptr_t read_buffer;
};

• 调用ioctl接收数据--ioctl(bs->fd, BINDER_WRITE_READ, &bwr);