linux – create / dev / fakeDevice支持read,write和ioctl

文档感觉有点稀缺(或者我正在查看错误的地方)并且提供的cuda示例中充满了其他一些处理参数或缓冲区处理的融合方式.所以这里有另一个例子(更简单,这里没有任何用处……)：

设备“驱动程序”(cusetest.c)：

#define FUSE_USE_VERSION 30
#define _FILE_OFFSET_BITS 64
#include <fuse/cuse_lowlevel.h>
#include <fuse/fuse_opt.h>

#include <stdio.h>

#define LOG(...) do { fprintf(stderr,__VA_ARGS__); puts(""); } while (0)

static void cusetest_open(fuse_req_t req,struct fuse_file_info *fi) {
    LOG("open");
    fuse_reply_open(req,fi);
}

static void cusetest_read(fuse_req_t req,size_t size,off_t off,struct fuse_file_info *fi) {
    LOG("read");
    fuse_reply_buf(req,"Hello",size > 5 ? 5 : size);
}

static void cusetest_write(fuse_req_t req,const char *buf,struct fuse_file_info *fi) {
    LOG("write (%u bytes)",size);
    fuse_reply_write(req,size);
}

static void cusetest_ioctl(fuse_req_t req,int cmd,void *arg,struct fuse_file_info *fi,unsigned flags,const void *in_buf,size_t in_bufsz,size_t out_bufsz) {
    LOG("ioctl %d: insize: %u outsize: %u",cmd,in_bufsz,out_bufsz);
    switch (cmd) {
    case 23:
        if (in_bufsz == 0) {
            struct iovec iov = { arg,sizeof(int) };
            fuse_reply_ioctl_retry(req,&iov,1,NULL,0);
        } else {
            LOG("  got value: %d",*((int*)in_buf));
            fuse_reply_ioctl(req,0);
        }
        break;
    case 42:
        if (out_bufsz == 0) {
            struct iovec iov = { arg,1);
        } else {
            LOG("  write back value");
            int v = 42;
            fuse_reply_ioctl(req,&v,sizeof(int));
        }
        break;
    }
}

static const struct cuse_lowlevel_ops cusetest_clop = {
        .open           = cusetest_open,.read           = cusetest_read,.write          = cusetest_write,.ioctl          = cusetest_ioctl,};

int main(int argc,char** argv) {
    // -f: run in foreground,-d: debug ouput
    // Compile official example and use -h
    const char* cusearg[] = {"test","-f","-d"};
    const char* devarg[]  = {"DEVNAME=cusetest" };
    struct cuse_info ci;
    memset(&ci,0x00,sizeof(ci));
    ci.flags = CUSE_UNRESTRICTED_IOCTL;
    ci.dev_info_argc=1;
    ci.dev_info_argv = devarg;

    return cuse_lowlevel_main(3,(char**) &cusearg,&ci,&cusetest_clop,NULL);
}

编译并运行：gcc -Wall -g -lfuse cusetest.c -o cusetest&& sudo ./cusetest

测试程序(testcusetest.c)：

#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <sys/ioctl.h>

int main() {
    int fd = open("/dev/cusetest",O_RDWR);

    const char* msg = "Fooooo";
    write(fd,msg,strlen(msg));

    int v = 63;
    ioctl(fd,23,&v);
    fprintf(stderr,"value is now: %dn",v);
    ioctl(fd,42,v);
    close(fd);
    return 0;
}

编译并运行：gcc -Wall testcusetest.c -o testcusetest&& ./testcusetest

它还有很多工作要做,但应该足以获得新手.陷阱是CUSE_UNRESTRICTED_IOCTL.如果in-或outputbuffer的长度为零,则需要使用fuse_reply_ioctl_retry()进行回复.将填充缓冲区再次调用回调.