On Sun, 26 Feb 2012, Alex Gershgorin wrote: > > Thanks Guennadi for your quick response , > > > > >Hi Alex > > > > > Hi Guennadi, > > > > > > We would like to use I.MX35 processor in new project. > > > An important element of the project is to obtain life video from the camera and display it on display. > > > For these purposes, we want to use mainline Linux kernel which supports all the necessary drivers for the implementation of this task. > > > As I understand that soc_camera is not currently supported userptr method, in which case how I can configure the video pipeline in user space > > > to get the live video on display, without the intervention of the processor. > > > > >soc-camera does support USERPTR, also the mx3_camera driver claims to > > >support it. > > > > I based on soc-camera.txt document. > > > Yeah, I really have to update it... > > > The soc-camera subsystem provides a unified API between camera host drivers and > > camera sensor drivers. It implements a V4L2 interface to the user, currently > > only the mmap method is supported. > > > > In any case, I glad that this supported :-) > > > > What do you think it is possible to implement video streaming without > > the intervention of the processor? > > >It might be difficult to completely eliminate the CPU, at the very least > >you need to queue and dequeue buffers to and from the V4L driver. To avoid > >even that, in principle, you could try to use only one buffer, but I don't > >think the current version of the mx3_camera driver would be very happy > >about that. You could take 2 buffers and use panning, then you'd just have > >to send queue and dequeue buffers and pan the display. But in any case, > >you probably will have to process buffers, but your most important > >advantage is, that you won't have to copy data, you only have to move > >pointers around. > > The method that you describe is exactly what I had in mind. > It would be more correct to say it is "minimum" CPU intervention and not without CPU intervention. > As far I understand, I can implement MMAP method for frame buffer device > and pass this pointer directly to mx3_camera driver with use USERPTR > method, then send queue and dequeue buffers to mx3_camera driver. > What is not clear, if it is possible to pass the same pointer of frame > buffer in mx3_camera, if the driver is using two buffers? Sorry, I really don't know for sure. It should work, but I don't think I tested thid myself nor I remember anybody reporting having tested this mode. So, you can either try to search mailing list archives, or just test it. Begin with a simpler mode - USERPTR with separately allocated buffers and copying them manually to the framebuffer, then try to switch to just one buffer in this same mode, then switch to direct framebuffer memory. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- 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
