Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 31 Oct 2006 17:00:59 +0100 | From | Jiri Slaby <> | Subject | Re: mmaping a kernel buffer to user space |
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Guillermo Marcus wrote: > Hi all, > > I recently run with the following situation while developing a PCI > driver. The driver allocates memory for a PCI device using > pci_alloc_consistent as this memory is going to be used to perform DMA > transfers. To pass the data from/to the user application, I mmap the > buffer into userspace. However, if I try to use remap_pfn_range > (>=2.6.10) or the older remap_page_range(<=2.6.9) for mmaping, it ends > up creating a new buffer, because they do not support RAM mapping, then > pagefaulting to the VMA and by default allocating new pages. Therefore, > I had to implement the nopage method and mmap one page at a time as they > fault. > > However, to my point of view, this is unnecessary. The memory is already > allocated, the memory is locked because it is consistent, and it may be > a (very small) performance and stability issue to do them one-by-one. > Why can't I simply mmap it all at once? am I missing some function? More > important, why can't remap_{pfn/page}_range handle it?
Piece of code please. pci_alloc_consistent calls __get_free_pages, and there should be no problem with mmaping this area.
regards, -- http://www.fi.muni.cz/~xslaby/ Jiri Slaby faculty of informatics, masaryk university, brno, cz e-mail: jirislaby gmail com, gpg pubkey fingerprint: B674 9967 0407 CE62 ACC8 22A0 32CC 55C3 39D4 7A7E - 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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