Messages in this thread | | | Date | Wed, 01 Nov 2006 16:06:20 +0100 | From | Guillermo Marcus Martinez <> | Subject | Re: mmaping a kernel buffer to user space |
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yogeshwar sonawane schrieb: > On 11/1/06, Guillermo Marcus Martinez <marcus@ti.uni-mannheim.de> wrote: >> Rolf Offermanns schrieb: >> > Guillermo Marcus <marcus <at> ti.uni-mannheim.de> writes: >> >> Note: I am using kernel 2.6.9 for these tests, as it is required by my >> >> current setup. Maybe this issue has already been addressed in newer >> >> kernel. If that is the case, please let me know. >> > >> > Have a look at this article: >> > >> > "The evolution of driver page remapping" >> > http://lwn.net/Articles/162860/ >> > >> > It should make things clearer. >> > >> > The "API changes in the 2.6 kernel series" page is also a very good >> read: >> > http://lwn.net/Articles/2.6-kernel-api/ >> > >> > HTH, >> > Rolf >> >> Thanks for the links! >> >> Yes, it looks like a step in the right direction. However, the article >> says about vm_insert_page(): "...What it does require is that the page >> be an order-zero allocation obtained for this purpose...", therefore >> making it also unusable for this case (mmaping a pci_alloc_consistent). >> >> I think the limitation (being order zero), is related to the page >> counting, as I understand that for bigger order allocations, only the >> first-page counter is incremented (not every page). If that is a >> problem, I guess I would also see a problem with my workaround, and I >> see none (yet). So I may try in a newer kernel and see if I can use it >> to walk the pages on the mmap without using the nopage(). > > Setting 'PG_reserved' bit of all allocated pages & then calling > remap_page/pfn_range() > will do the things for 2.6.9. >
I will give it a try. I guess it may not be equivalent to setting VM_RESERVED before calling remap_page/pfn_range(). Is this platform specific, or is intended behavior/usage of remap_page/pfn_range()?
>> >> My suggestion would be to add two functions: pci_map_consistent() and >> dma_map_coherent() to address this issue, and their corresponding >> unmap's. That will make sure all that is needed is done, is a clean and >> consistent with the pci_ and dma_ APIs, and fills a mmap requirement not >> covered by the other functions. >> >> Best wishes, >> Guillermo >> >> - >> 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/ >> > - > 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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