Messages in this thread | | | Date | Fri, 08 Aug 2014 16:25:58 -0700 | From | Laura Abbott <> | Subject | Re: [PATCHv6 3/5] common: dma-mapping: Introduce common remapping functions |
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On 8/8/2014 3:45 PM, Andrew Morton wrote: > On Fri, 8 Aug 2014 13:23:15 -0700 Laura Abbott <lauraa@codeaurora.org> wrote: > >> >> For architectures without coherent DMA, memory for DMA may >> need to be remapped with coherent attributes. Factor out >> the the remapping code from arm and put it in a >> common location to reduce code duplication. >> >> As part of this, the arm APIs are now migrated away from >> ioremap_page_range to the common APIs which use map_vm_area for remapping. >> This should be an equivalent change and using map_vm_area is more >> correct as ioremap_page_range is intended to bring in io addresses >> into the cpu space and not regular kernel managed memory. >> >> ... >> >> @@ -267,3 +269,68 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, >> return ret; >> } >> EXPORT_SYMBOL(dma_common_mmap); >> + >> +/* >> + * remaps an allocated contiguous region into another vm_area. >> + * Cannot be used in non-sleeping contexts >> + */ >> + >> +void *dma_common_contiguous_remap(struct page *page, size_t size, >> + unsigned long vm_flags, >> + pgprot_t prot, const void *caller) >> +{ >> + int i; >> + struct page **pages; >> + void *ptr; >> + >> + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL); >> + if (!pages) >> + return NULL; >> + >> + for (i = 0; i < (size >> PAGE_SHIFT); i++) >> + pages[i] = page + i; > > Assumes a single mem_map[] array. That's not the case for sparsemem > (at least). > >
Good point. I guess the best option is to increment via pfn and call pfn_to_page. Either that or go back to slightly abusing ioremap_page_range to remap normal memory.
Thanks, Laura
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