文章目录前言1位bit2位操作bitops定义实现arm64的实现arm的实现示例3bitfind定义示例1示例24bitmap定义使用宏BITS_TO_LONGS直接定义使用宏DECLARE_BITMAP

文章目录定义物理意义内核应用应用一：直接使用应用二间接使用测试驱动层示例应用层示例参考定义BITS_TO_LONGS定义在include/linux/bitops.h中，具体如下#defineBITS_PER_BYTE8

typedefstructcpumask{DECLARE_BITMAP(bits,NR_CPUS);}cpumask_t;#defineDECLARE_BITMAP(name,bits)\unsignedlongname[BITS_TO_LONGS

函数用于初始化位图源码如下：/**@dst:位图的起始地址*@nbits:位图的个数*/staticinlinevoidbitmap_zero(unsignedlong*dst,intnbits){intlen=BITS_TO_LONGS

linux提供了相关的接口进行初始化和操作bitmap.include/linux/types.h#defineDECLARE_BITMAP(name,bits)\unsignedlongname[BITS_TO_LONGS

structinput_dev{constchar*name;//输入设备名constchar*phys;constchar*uniq;structinput_idid;unsignedlongevbit[BITS_TO_LONGS

constchar*name;//设备名字constchar*phys;constchar*uniq;structinput_idid;//用于匹配事件处理层handlerunsignedlongpropbit[BITS_TO_LONGS

defineBITS_TO_LONGS(x)(((x)+BITS_PER_LONG-1)/BITS_PER_LONG)   intmain(void){inti=40;intj=1000;printf("%d\n",BITS_TO_LONGS

3constchar*phys; 4constchar*uniq; 5structinput_idid;//与input_handler匹配用的id 6 7unsignedlongevbit[BITS_TO_LONGS

利用linux内核所提供的input子系统编写字符设备驱动的步骤：包含头文件：#include涉及核心接口体：structinput_dev{ ......... unsignedlongevbit[BITS_TO_LONGS

unsignedlongevbit[BITS_TO_LONGS(EV_CNT)];//用于描述设备所产生数据的事件分类   unsignedlongkeybit[BITS_TO_LONGS(KEY_CNT

name;设备名constchar*phys;设备在系统中路径constchar*uniq;structinput_idid;用于匹配inputhander参数unsignedlongpropbit[BITS_TO_LONGS

Linux内核中的BITS_TO_LONGS宏的作用下面BITS_TO_LONGS这个宏定义经常出现在内核中。

[linux-3.0]BITS_TO_LONGS定义在：include/linux/bitops.h#defineBITS_PER_BYTE    8#defineBITS_TO_LONGS(nr)  

        constchar*phys;        constchar*uniq;        structinput_idid;         unsignedlongpropbit[BITS_TO_LONGS

;//设备系统层的物理路径 constchar*uniq;// structinput_idid;//输入设备id总线类型;厂商编号,产品id,产品版本 unsignedlongevbit[BITS_TO_LONGS

[linux-3.0]BITS_TO_LONGS定义在：include/linux/bitops.h#defineBITS_PER_BYTE    8#defineBITS_TO_LONGS(nr)  

structinput_dev{ constchar*name; constchar*phys; constchar*uniq; structinput_idid; unsignedlongpropbit[BITS_TO_LONGS

[linux-3.0]BITS_TO_LONGS定义在：include/linux/bitops.h#defineBITS_PER_BYTE    8#defineBITS_TO_LONGS(nr)  

假设BITS_PER_LONG为32bit，NR_CPUS为.那么，constunsignedlongcpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS