Re: DMA transfer with kiobuf, kernel 2.4.21

[sej <trash@aie-etudes.com>]

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

I can't because I need to allocate 128MB of memory per PCI card and if I put for example 4 cards, I'll have 512MB in kernel memory, and I think there will be some problem in kernel.



> 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!

I have a plx bridge PCI9656 with a DMA controler. So I have to make a 
descriptor table with physical address and size.
I work in 32 bits address mode, but I don't know which function to call 
to get a 36bits address for my controler.

Regards.
Sebastien


> 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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