Messages in this thread | | | Subject | Re: allocation failed: out of vmalloc space error treating and VIDEO1394 IOC LISTEN CHANNEL ioctl failed problem | From | David Moore <> | Date | Mon, 15 Jan 2007 14:54:40 -0500 |
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On Mon, 2007-01-15 at 10:20 -0800, Arjan van de Ven wrote: > if you need that much you probably should redesign your algorithms to > not need vmalloc in the first place....
I think you've convinced me that vmalloc is not a good choice when a driver needs a large buffer (many megabytes) for DMA.
In this case, we need a large ring buffer for reception of isochronous packets from a firewire device. If I understand you correctly, you are suggesting that this buffer be obtained as followed:
1. Application performs malloc() in user-space and mmap()s it. 2. Driver uses vmalloc_to_page() on every page of the malloc'ed memory and constructs a scatter-gather list. 3. Map the sg list with pci_map_sg(). 4. Commence DMA.
Is that correct? In particular, does it do the right thing in terms of pinning the memory and dealing with high memory?
I notice that the block I/O API has some convenience functions for this, but this is not a block device. Are there some other convenience functions that can be used?
Forgive me if these are obvious questions -- I'm not the developer of video1394, but I'd still like get it right for the new firewire stack that's being developed.
Thanks,
David
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