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    SubjectRe: DMA transfer with kiobuf, kernel 2.4.21
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    On Tue, 2005-11-15 at 18:39 +0100, sej wrote:
    > Hi,
    > I allocate a big chunck of memory from user space with :
    >
    > #define MEM_SIZE_DMA (128*1024*1024)
    > // allocate 128MB of memory
    > void *_pVirtualMem = memalign(sysconf(_SC_PAGESIZE), MEM_SIZE_DMA);
    >
    > // Reserve memory
    > memset(_pVirtualMem, 0, MEM_SIZE_DMA);
    >
    > // Lock memory
    > if (!mlock(_pVirtualMem, MEM_SIZE_DMA ))
    > {
    > free(_pVirtualMem);
    > return false;
    > }
    >
    > Then I call an IOCTL from my driver (DmaMapDescrpImg) to create a DMA
    > scatter gather list.

    that sounds the wrong approach.. why don't you make your device driver
    export an mmap function.. and let the userspace app use that ?


    >
    > transfer->Descript[i].size = PAGE_SIZE;
    > transfer->Descript[i].pciaddr = (ULONG)
    > virt_to_phys(page_address(iobuf->maplist[idxIobuf]));

    you really need to use the PCI DMA mapping api!



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