Messages in this thread | | | Date | Wed, 16 Nov 2005 09:35:45 +0100 | From | sej <> | Subject | Re: DMA transfer with kiobuf, kernel 2.4.21 |
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Hi, thank you for your help. I will read the DMA documentation. But I need to make DMA on User memory space allocated in user space. Because I don't want the kernel to make allocation and deallocation during execution for stability. Best regards. Sebastien
Arjan van de Ven wrote :
>On Tue, 2005-11-15 at 18:53 +0100, sej wrote: > > >>>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. >> >> > >no there isn't.. there is no rule that memory you allocate for this as >to be lowmem... at all. > > > >> >> >> >>>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. >> >> > >see the PCI DMA mapping api. the docs for it are in Documentation/ > > > >- >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ > > > >
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