Hi Hans, On Monday 26 September 2011 12:55:05 Hans Verkuil wrote: > On Thursday, September 15, 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. > > > > > > Hi Laurent, > > > > > > 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? > > > > Hi Cliff, > > > > 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> > > That reminds me: Laurent, this should really be moved to v4l-utils.git. > Any progress on that? There are several pending patches for media-ctl that I want to apply first. BTW, the MC API is not restricted to V4L devices. Wouldn't it be a bad signal for the MC API adoption to move media-ctl to v4l-utils ? -- 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
