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!
>
>
>
>
>
>  
>