Hi Sylwester, Sylwester Nawrocki wrote: > On 02/04/2012 12:22 PM, Sakari Ailus wrote: >> Sylwester Nawrocki wrote: >>> On 02/01/2012 11:00 AM, Sakari Ailus wrote: >>>> I'd guess that all the ISP would do to such formats is to write them to >>>> memory since I don't see much use for either in ISPs --- both typically are >>>> output of the ISP. >>> >>> Yep, correct. In fact in those cases the sensor has complicated ISP built in, >>> so everything a bridge have to do is to pass data over to user space. >>> >>> Also non-image data might need to be passed to user space as well. >> >> How does one know in the user space which part of the video buffer >> contains jpeg data and which part is yuv? Does the data contain some >> kind of header, or how is this done currently? > > There is an additional data appended to the image data. Part of it must > be retrieved out of the main DMA channel. I someway missed to mention in > the previous e-mails that the bridge is somehow retarded, probably because > of the way is has been evolving over time. That is, it originally > supported only the parallel video bus and then a MIPI-CSI2 frontend was > added. So it cannot split MIPI-CSI data channels into separate memory > buffers, AFAIK - at this stage. I think it just ignores the VC field of > the Data Identifier (DI), but it's just a guess for now. > > If you look at the S5PV210 datasheet and the MIPI-CSIS device registers, > at the end of the IO region it has 4 x ~4kiB internal buffers for > "non-image" data. These buffers must be emptied in the interrupt handler > and I'm going to need this data in user space in order to decode data > from sensors. > > Sounds like a 2-plane buffers is a way to go, one plane for interleaved > YUV/JPEG and the second one for the "metadata". > > I originally thought about a separate buffer queue at the MIPI-CSIS driver, > but it likely would have added unnecessary complication in the applications. > >> I'd be much in favour or using a separate channel ID as Guennadi asked; >> that way you could quite probably save one memory copy as well. But if >> the hardware already exists and behaves badly there's usually not much >> you can do about it. > > As I explained above I suspect that the sensor sends each image data type > on separate channels (I'm not 100% sure) but the bridge is unable to DMA > it into separate memory regions. > > Currently we have no support in V4L2 for specifying separate image data > format per MIPI-CSI2 channel. Maybe the solution is just about that - > adding support for virtual channels and a possibility to specify an image > format separately per each channel ? > Still, there would be nothing telling how the channels are interleaved :-/ _If_ the sensor sends YUV and compressed JPEG data in separate CSI-2 channels then definitely the correct way to implement this is to take this kind of setup into account in the frame format description --- we do need that quite badly. However, this doesn't really help you with your current problem, and perhaps just creating a custom format for your sensor driver is the best way to go for the time being. But. When someone attaches this kind of sensor to another CSI-2 receiver that can separate the data from different channels, I think we should start working towards for a correct solution which this driver also should support. With information on the frame format, the CSI-2 hardware could properly write the data into two separate buffers. Possibly it should provide two video nodes, but I'm not sure about that. A multi-plane buffer is another option. Cheers, -- Sakari Ailus sakari.ailus@xxxxxx -- 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
