On Tue, Nov 17, 2015 at 3:54 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > On 11/17/15 14:15, Ran Shalit wrote: >> On Tue, Nov 17, 2015 at 9:53 AM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: >>> On 11/17/2015 08:39 AM, Ran Shalit wrote: >>>> Hello, >>>> >>>> I intend to use cobalt driver as a refence for new pci v4l2 driver, >>>> which is required to use several input simultaneously. for this cobalt >>>> seems like a best starting point. >>>> read/write streaming will probably be suffecient (at least for the >>>> dirst debugging). >>>> The configuration in my cast is i7 core <-- pci ---> fpga. >>>> I see that the dma implementation is quite complex, and would like to >>>> ask for some tips regarding the following points related to dma issue: >>>> >>>> 1. Is it possible to do the read/write without dma (for debug as start) ? >>> >>> No. All video capture/output devices all use DMA since it would be prohibitively >>> expensive for the CPU to do otherwise. So just dig in and implement it. >>> >> >> Hi, >> >> Is the cobalt or other pci v4l device have the chip datasheet >> available so that we can do a reverse engineering and gain more >> understanding about the register read/write for the dma transactions ? >> I made a search but it seems that the PCIe chip datasheet for these >> devices is not available anywhere. > > Sorry, no, it's not publicly available. > > But they all work along the same lines: each DMA descriptor has a > PCI DMA address (where the data should be written to in memory), the length > (bytes) of the DMA transfer and the pointer to the next DMA descriptor (chaining > descriptors together). Finally there is some bit to trigger and interrupt when > the full frame has been transferred. > Thank you all very much for all these valuable information ! I must admit that when I observe the source examples, it seems quite complex, (at least much more complex than the driver I am familiar with, which most of them time is taking a functional example and understanding what to change and how, or writing simple drivers.... ) If there are any other tips and ideas about debug/testing/development steps when doing pci v4l device driver please tell me. Thank you all very much, Ran -- 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
