V4L2驱动程序架构

1、1V4L2简介video41inux2(V4L2)是Linux内核中关于视频设备的内核驱动，它为Linux中视频设备访问提供了通用接口，在Linux系统中，V4L2驱动的Vide。设备节点路径通常/dev/video/中的videoXV4L2驱动对用户空间提供字符设备，主设备号为81,对于视频设备，其次设备号为0-63。除此之外，次设备号为64-127的Radio设备，次设备号为192-223的是Teletext设备，次设备号为224-255的是VBI设备V4L2驱动的Vide。设备在用户空间通过各种ioctl调用进行控制，并且可以使用mmap进行内存映射1.1V4L2驱动主要使用的ioctl

2、命令值如下所示:ttdefineVIDIOC_QUERYCAP_I0R(，V，,0,structv412_capability)/*查询能力*/ftdefineVIDI0_G_FMT_I0WR(，V，,4,structv412_format)/*获得格式*/ftdefineVIDI0C_S_FMT_I0WR(V,5,structv412_format)/*设置格式*/ttdefineVIDIOC_REQBUFS_I0WR(，V，,8,strutv412_requestbuffers)/*申请内存*/ftdefineVIDI0C_G_FBUF_I0W(V,10,structv412_frameb

3、uffer)/*获得Framebuffer*/ftdefineVIDI0C_S_BUF_I0WfV11,structv412_framebuffer)/*设置Framebuffer*/ttdefineVIDI0C_0VERLAY_I0W(，V，,14,int)/*设置Overlay*/ttdefineVIDIOC_QBUF_I0WR(，V，,15,structv412_buffer)/*将内存加入队歹！J*/defineVIDIOC_DQBUF_I0WR(V,17,strutv412_buffer)/*从队列取出内存*/defineVIDIOC_STREAMON_I0W(V,1&int)/*开

4、始流*/defineVIDIOC_STREAMOFF_I0W(V,19,int)/*停止流*/ttdefineVIDIOC_G_CTRL_I0WR(，V，,27,structv412_control)/*得到控制*/ttdefineVIDIOC_S_CTRL_I0WR(，V，,2&structv412_control)/*设置控制*/1.2重要结构头文件mclude/liiiux./videodev2.11mclude/media/v412-deT.hV4L2驱动核心实现文件：dnver/media/video/v412dev.cv412-dev.h中定义的video_device是V4L2驱

5、动程序的核心数据结构strnctvideo_deviceconststrnctv412_file_operations*fbps;stmctcdev*cdev;/字符设备stmctdevice*parent;/父设备stmctv412device*v412dev;/父v412devicechariiame32;/名称mtvfl_type;类型mtminor;/次设备号/*释放回调1*7void(*release)(structvideo_device*vdev);/*ioctl回调*/conststmctv412_ioctl_ops*ioctl_ops;常用的结构参M/include/lmux

6、/videodev2.h设备能力结构stiuctv412_capability_u8dnver16;驱动名_u8card32;/例如HauppaugewinTV_u8biis_info32/PCI总线信息_u32version;/内核版本_u32capabilities;/设备能力_u32reserved4;；数据格式结构stiuctv412_fonnatenumv412_bu匚typetype;/本结构的数据类型；像素格式结构stiuctv412_pix_fonnat_u32width;/宽度_u32height;/高度请求缓冲stiuctv412_requestbuffersu32coun

7、t;/缓存数量enumv412_bu匚typetype;/数据流类型数据流类型包括V4L2_MEMORY_MMAP和V4L2IEMORY_USERPTRenumv412_memory;2V4L2驱动注册2.1video.register.devicevideo41mux2驱动程序的注册dnvers/mediaAideovideo_register_device函数用来注册一个v41驱动程序mtvideo_register_device(stinctvideo_device*vdev?mttype,intnr)return_video_register_device(vdev?type,m1);

8、其中参数type支持的类型如下#defineTL_TYPE_GRABBER0视频#defiiieTL_TYPE_PI1/从视频消隐的时间取得信息的设备#defineTL_TYPE_RADIO2/、播#defineTL_TYPE_VTX3视传设备#defineTL_TYPEJ4AX4/最k值返回调用_video_register_device()_video_register_device函数先检查设备类型，接卜来牙找一禾可用设备号，最后注册相应的字符设备staticmt_video_iegister_device(structvideo_device*vdev,mttype,mtnr,intw

9、am_i匚nr_in_use)switch(type)caseTL_TYPE_GRABEERjnimor_offset=0;nimor_cnt=64:break;caseTL_TYPE_RADIO:nimor_offset=64;nimor_cnt=64:break;caseTL_TYPE_VTX:nimor_offset=192;nimorent=32;break;caseTL_TYPE_n：ninior_offset=224;nimor_cnt=32;break;nr=devnode_find(vdev,nr=1?0m;minor_cnt);nr=devnode_find(vdev?nr=

10、1?0:m;minor_cnt);vdev-cdev-ops=&v412_fops;注册字符设备ret=cdev_add(vdev-cdev,RIKDE*V(TDEO_MAJOR,vdev-ninor),1);ret=device_register(&vdev-dev);注册完毕设备看息存储在video_device数组中mutex_lock(&videodev_lock);ideo_devicevdev-minor=vdev;mutex_unlock(&videodev_lock);2.2V4I2Jops接口v412_fops为video41inux2设备提供了统一的应用层接II,v412_

11、fops定义如卞staticconststiuctfile_operationsv412_fops=owner=THIS_MODULE,.read=v412_read?.write=v412_write,.open=v412_open,.get_unmapped_area=v412_get_immapped_area,.lmiiap=v412_mmap,.milockedloctl=v412ioctL.release=v412_release,.poll=v412_poll,.llseek=nollseek,;v412_fops中的成员函数最终要调用structvideo_device-fop

12、s中相应的成员structvideo_device-fbps是具体video41mux2摄像头驱动程序必须实现的接I1staticssize_tv412_read(structfilecliar_user*buf,size_tsz,lofft*off)returnvdevfbpsread(fnp,buf,sz,off)；2.3/drivers/media/video/samsung/fimc/s3c_fimc_core.c驱动探测函数s3c_func_probe定义staticmts3c_fimc_piobe(structplatfbnn_device*dev)Ctrl=s3c_fimc_re

13、gister_controller(pdev);clk_enable(ctrl-clock);/使能时钟注册V4L2驱动ret=video_register_device(ctrl-vd,ATL_TYPE_GRABBER,ctil-id);s3c_fiiiic_register_contoller函数主要用来分配资源与申请中断staticstrncts3c_fimc_control*s3c_fimc_register_controller(stnictplatfonn_device*pdev)ctrl-vd=&s3c_fimc_video_devicei(l;申请中断ctrl-u-q=plat

14、fbnn_get_irq(pdev?0);if(request_irq(ctrl-irq,s3c_fimc_irq,IRQF_DISABLED,ctrl-iiame,Ctrl);structvideo_devices3c_finic_video_deviceS3C_FIN!C_MAX_CTRLS=0=.vfljype=MD_TYPE_OTRLAY|VID_TYPE_CAPTURE|1D_TYPE_CLIPPING|门D_TYPE_SCALES,.fops=&s3c_fimc_fops,.ioctl_ops=&s3c_fimc_v412_ops,.release=s3cfiincvdevrele

15、ase,.name=sc3_video0,s3c_fiinc_v412_ops,是在diivers/mediXideo/sanisung/fimc中实现的v412_ioctl_ops,在用户空间进行ioctl等调用时，要调用到具体实现的各个函数指针3V4L2操作3.1s3c_fimc_openstaticmts3c_fiinc_open(stiiictfile*filp)stmcts3cfiinccontrol*ctrl;mtid,ret;id=0;Ctrl=&s3c_fimc.ctrlid;mutex_lock(&ctrl-lock);if(atomic_read(&ctrl-in_use)

16、ret=-EBUSY;gotoresource_busy;elseatomic_inc(&ctil-in_use);s3c_fimc_reset(ctrl);filp-private_data=Ctrl;miitex_unlock(&ctiLlock);return0;resource_btisy:miitex_unlock(&ctiLlock);returnret;用户空间打开设备文件fd=open(dev_iiame,O_RDWR|ONONBLOCK,0);3.2获取设备的capability,查看设备有什么功能结构体stmctv412_capabilitycap;ret=ioctl(fd

17、,TDIOC_QUERYCAP,&cap);/includelinux/videodev2.hstructv412_capability_u8driver16;/*i.e.”bttv”*/_u8card32;/*i.e.HauppaugeWinTV”*/_u8bus_infb32;/*nPCI:H+pci_name(pci_dev)/_u32version;/*shoulduseKERNEL_RSION()*/_u32capabilities;/*Devicecapabilities*/_u32resenred4;；2）驱动实现staticmts3c_fimc_v412_querycap(st

18、iuctfile*filp,void*fh,stmctv412_capability*cap)stmcts3cfiinccontrol*ctrl=(stmcts3cfiinccontrol*)fh;strcpy(cap-diiver,”SamsungFIMCDnvern);strlcpy(cap-card,ctil-vd-iiame?sizeof(cap-card);spnntf(cap-bus_uifd,”FIMCAHB-bus11);capversioii=0;cap-capabilities=(SL2_CAP_VIDEO_O、王RLAY|SL2_CAP_VIDEO_CAPTURE|V4L

19、2_CAP_STREAMING);return0;3)应用层调用staticmtvideo_capability(mtfd)mtret=0;stmctv412_capabilitycap;ret=ioctl(fd,TDIOC_QUERYCAP,&cap);if(ret=S3C_FIMC_MAX_INPUT_TYPES)retiun-EINAAL;ctrl-v412.mput=&s3c_fimc_mput_typesi;if(s3c_fimc_input_typesi.type=V4L2_INPUT_TYPE_CAMERA)ctrl-uvtype=PATH_IN_rrU_CAMERA;elsec

20、tii-iii_type=PATH_IN_DMA;return0;staticstiuctv412_inputs3c_fimc_input_types=.index=0,.name=ExternalCameraInput,type=V4L2_INPUT_TYPE_CAMERA,.audioset=1,timer=0,.std=V4L2STDPALBG|V4L2STDNTSCM5,.status=0,.index=1,.name=MemoryInput11,type=V4L2_INPUT_TYPE_MEMORY,.audioset=2,timer=0,.std=V4L2STDPALBG|V4L2

21、STDNTSCM,.status=0,；staticmts3c_fimc_v412_eiium_input(structfile*filp,void*fli,stmctv412_mput*i)if(i-index=S3C_FIMC_MAX_INPUT_TYPES)retiun-EINAAL;memcpy(i,&s3c_fimc_mpiit_typesi-mdex,sizeof(stnictv412_input);return0;3)应用staticmtvideo_mput(intfd)/*+*getandsettlieA7DIOINPUT*/mtret=0;stmctv412_inputmpu

22、t;视频输入信息,对应命令A1DIOC_ENUNIINPUTmtindex;mdex=0;/0-Conositeinput,1-S-Videomput.ret=loctl(fd,VIDIOCSINPUT,&index);if(ret0)perror(rTDIOC_S_INPUT”)；retiunret;mput.mdex=mdex;ret=loctl(fd,VIDIOC_ENUMINPUX&input);if(retmdex;if(index=S3C_FIWIC_MAX_CAPTURE_FORMATS)retiun-EINAAL;meinset(f?0,sizeof(*f)；memcpy(f5

23、ctil-v412.fintdesc+index,sizeof(*f);return0;#defineS3C_FIMC_MAX_CAPTURE_FORMATSARRAY_SIZE(s3c_fimc_capture_foimats)conststaticstiuctv412_fintdescs3c_fiinc_captiu-e_fbnnats=.indextype.flagsdescriptionpixelfoniiat=0?=V4L2BUFTYPEMDEOCAPTURE,=FORMATFLAGSPLANAR.=n4:2:0,planar,Y-Cb-Cf=V4L2PIXFMTYUV420,tII

24、II.index=1,type=V4L2BUF_TYPEjnDEO_CAPTURE,.flags=FORKIAT_FLAGS_PLANAR：.description=”422,planar,Y-Cb-Crn,.pixelfoniiat=V4L2_PIX_FMT_YUV422R.indextype.flagsdescriptionpixelfoniiat=2,=V4L2BUFTYPEMDEOCAPTURE,=FORMATFLAGSPACKED,=”422,packed,YCBYCR役=V4L2_PIX_FMT_YUY；.indextype.flagsdescriptionpixelfoniiat

25、=3,=V4L2BUFTYPEMDEOCAPTURE,=FORMATFLAGSPACKED,=”422,packed,CBYCRY蔦=V4L2_PIX_FMT_UYAH；conststaticstiuctv412fintdescs3c_finic_overlay_fbrmats=.indextype.flagsdescriptionpixelfoniiat=0?=V4L2JBUF_TYPEJUDEO_O王RLAY,=FORMATFLAGSPACKED,=n16bppRGBJeK,=V4L2_PIX_FMT_RGE565,.index=1,type=V4L2JBUF_TYPEJUDEO_O王RL

26、AY,.flags=FORKIAT_FLAGS_PACKED,description=”24bppRGB,len,.pixelfomiat=V4L2_PIX_FMT_RGB24,;3）应用层staticmtvideo_fiiitdesc(mtfd)mtret=0;stmctv412_fintdescfintdes;CLEAR(fintdes);fintdes.index=0;fintdes.type=V4L2_BUF_TYPE_TDEO_CAPTURE;prmtf(Hn*vidiocenumerationstreamformatuiforniations:*nM);while(1)ret=io

27、ctl(fd,TDIOC_ENUM_FMT,&fintdes);if(retv412.fimbuf.fint=f-fiiit.pix;if(f-fiiit.pix.pnv=4L2_FMT_IN)s3c_fimc_set_input_fiame(ctrr&ffint.pix);elses3c_fimc_set_output_&ame(ctrl,&ffint.pix);return0;mts3c_fimc_set_inpiit_fiame(structs3c_fiinc_control*ctrl,stiuctv412_pix_fonnat*fint)s3c_fimc_set_mput_foniia

28、t(ctrl,fint);return0;staticvoids3c_fimc_set_input_fbmiat(structs3c_fimc_coiitrol*ctrtstmctv412jpix_format*fiiit)stmcts3cfiincinframe*frame=&ctrl-mframe;frame-width=五width;frame-height=fint-height;switch(fint-pixelfbniiat)caseSL2_PIX_FMT_RGE565:fi-ame-fbnnat=FORMAT_RGB565;frame-planes=1;break;case4L2

29、_PIX_FMT_RGB24:fi-ame-fbnnat=FORMAT_RGB888;frame-planes=1;break;caseSL2_PIX_FMT_NV12:frame-fbniiat=FORMAT_YCBCR420;frame-planes=2;frame-ordei,_2p=LSBCBCR;break;caseSL2_PIX_FMT_NV21:frame-fbniiat=FORMAT_YCBCR420;frame-planes=2;frame-ordei,_2p=LSB_CRCB;break;caseSL2_PIX_FMT_NV12X:frame-fbniiat=FORMAT_

30、YCBCR420;frame-planes=2;frame-ordei_2p=MSB_CBCR;break;caseSL2_PIX_FMT_NV21Xiframe-fbniiat=FORMAT_YCBCR420;frame-planes=2;frame-ordei_2p=MSB_CRCB;break;case4L2_PIX_FMT_YUV42(kframe-fbniiat=FORMAT_YCBCR420;frame-planes=3;break;caseSL2_PIX_FMT_YUYVframe-fbniiat=FORMAT_YCECR422;frame-planes=1;frame-orde

31、ilp=IN_ORDER422_YCEYCR;break;case4L2_PIX_FMT_YYUframe-fbmiat=FORMAT_YCECR422;frame-plaiies=1;frame-ordeilp=IN_ORDER422_YCRYCB;break;casef4L2_PIX_FMT_UYY:frame-fbmiat=FORMAT_YCECR422;frame-plaiies=1;frame-ordeilp=IN_ORDER422_CEYCRY;break;caseSL2_PIX_FMT_mY:frame-fbmiat=FORMAT_YCECR422;frame-plaiies=1

32、;frame-ordeilp=IN_ORDER422_CRYCBY;break;caseSL2_PIX_FMT_NV16】frame-fbmiat=FORMAT_YCECR422;frame-plaiies=2;frame-ordei,_lp=LSBCBCR;break;caseSL2_PIX_FMT_NV61:frame-fbmiat=FORMAT_YCECR422;frame-plaiies=2;frame-ordei,_lp=LSB_CRCB;break;caseSL2_PIX_FMT_NV16Xframe-fbmiat=FORMAT_YCECR422;frame-plaiies=2;f

33、rame-ordei,_lp=MSB_CBCR;break;caseSL2_PIX_FMT_NV61X:frame-fbmiat=FORMAT_YCECR422;frame-plaiies=2;frame-ordei,_lp=MSB_CRCB;break;caser4L2PIXFMTYUV422P】frame-fbmiat=FORMAT_YCBCR422;fi-ame-planes=3;break;应用层staticmtvideo_setfhit(intfd)/$*setsti-eamdatafonnat*/iiitret=0;stiuctv412_fbnnatfint;CLEAR(fint)

34、;fint.type=SL2_EUF_TYPE_1DEO_CAPTURE;fint.fint.pix.width=640;fint.fint.pix.height=480;fint.fiiit.pix.pixelfonnat=V4L2_PIX_FMT_YUY：/foiPALfint.fint.pix.field=V4L2_FIELD_INTERLACED;ret=ioctl(fd,TDIOC_S_FMI；&伍it);if(retEnt.pix,0,size);memcpy(&f-fint.pix5&(ctil-v412.fimbuf.fint),size);return0;2）应用static

35、mtvideo_getfhit(intfd)mtret=0;stmctv412_fbnnatfoit;CLEAR(fint);fint.type=SL2_BUF_TYPE_nDEO_CAPTURE;ret=ioctl(fd,TDIOC_G_FMI；&fint);if(retmemory!=SL2_MEMORY_MMAP)eiT(”V4L2_MEMORY_MMAPisonlysupportedain);retiun-EINAAL;/*conti-oluserinput*/if(b-count4)b-count=4;elseif(b-coiuitcount=1;return0;staticmts3

36、c_fimc_v412_querybuf(structfile*filp,void*fh,stmctv412_buffer*b)stmcts3c_fiinc_control*ctrl=(stincts3c_fimc_control*)fh;if(b-type!=V4L2_BUF_TYPE_TDEO_O、卫RLAY&bfype!=V4L2JBUF_TYPE_TDEO_CAPTURE)retiun-EINAAL;if(b-menioiy!=4L2_MEMORY_MMAP)retiun-EINAAL;b-length=ctrl-out_framebusize;/*NOTE:weusethem.off

37、setasanindexformultipleframesout.Becauseallframesarenotcontiguous,wecannotuseitasonginalpurpose.Theindexvalueusedtofindoutwhichframeuserwantstorninap.*/b-m.offset=b-index*PAGE_SIZE;return0;staticmts3c_fimc_v412_qbuf(structfilevoid*fli,stmctv412_buffer*b)return0;应用层staticmtvideo_imnap(intfd)/*stepl*requestbufiersAllocatingMemoiy*/mtret=0;stmctv412_requestbuffersreq;CLEAR(req);req.coiuit=4;req.type=SL2_BUF_TYPE_TDEO_CAPTURE;req.memoty=4L2_WIEMORY_MMAP;ret=