Re: DMA transfer with kiobuf, kernel 2.4.21

[Arjan van de Ven <arjan@infradead.org>]

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!