Hi Cliff, On Thursday 15 September 2011 19:10:52 Sakari Ailus wrote: > Cliff Cai wrote: > > On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart wrote: > >> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote: > >>> Dear guys, > >>> > >>> I'm currently working on a camera/ISP Linux driver project.Of course,I > >>> want it to be a V4L2 driver,but I got a problem about how to design > >>> the driver framework. > >>> let me introduce the background of this ISP(Image signal processor) a > >>> little bit. > >>> 1.The ISP has two output paths,first one called main path which is > >>> used to transfer image data for taking picture and recording,the other > >>> one called preview path which is used to transfer image data for > >>> previewing. > >>> 2.the two paths have the same image data input from sensor,but their > >>> outputs are different,the output of main path is high quality and > >>> larger image,while the output of preview path is smaller image. > >>> 3.the two output paths have independent DMA engines used to move image > >>> data to system memory. > >>> > >>> The problem is currently, the V4L2 framework seems only support one > >>> buffer queue,and in my case,obviously,two buffer queues are required. > >>> Any idea/advice for implementing such kind of V4L2 driver? or any > >>> other better solutions? > >> > >> Your driver should create two video nodes, one for each stream. They > >> will each have their own buffers queue. > >> > >> The driver should also implement the media controller API to let > >> applications discover that the video nodes are related and how they > >> interact with the ISP. > > > > As "Documentation/media-framework" says, one of the goals of media > > device model is "Discovering a device internal topology,and > > configuring it at runtime".I'm just a bit confused about how > > applications can discover the related video notes? Could you explain > > it a little more? > > The major and minor numbers of video nodes are provided to the user > space in struct media_entity_desc (defined in include/linux/media.h) > using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define > which device node corresponds to the video device; this isn't trivial > for an application to do so there's a library which makes it easier: > > <URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary> > > See src/media.h for the interface. An example how to use this is > available in src/main.c. > > Entities the type of which is MEDIA_ENT_T_DEVNODE_V4L are V4L2 device > nodes. http://www.ideasonboard.org/media/omap3isp.ps shows a device topology example generated automatically from the output of the media-ctl tool. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
