Messages in this thread Patch in this message | | | Date | Wed, 13 Apr 2005 12:19:37 +0100 | From | Russell King <> | Subject | Re: mmap + dma_alloc_coherent |
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On Wed, Apr 13, 2005 at 12:43:47PM +0200, Rolf Offermanns wrote: > I would like to mmap a kernel buffer, allocated with pci_alloc_consistent() > for DMA, to userspace and came up with the following. Since there seem to be > some (unresolved) issues (see below) with this and I would like to do the > RightThing(TM), I would appreciate your comments about my stuff.
This has come up before. ARM implements dma_mmap_*() to allow this to happen, but it never got propagated to the other architectures.
Here's the (untested) x86 version. There may be a problem with x86 not marking the pages reserved, which is required for remap_pfn_range() to work.
diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x '*.orig' -x '*.rej' -r orig/arch/i386/kernel/pci-dma.c linux/arch/i386/kernel/pci-dma.c --- orig/arch/i386/kernel/pci-dma.c Mon Apr 4 22:52:57 2005 +++ linux/arch/i386/kernel/pci-dma.c Mon Apr 4 22:44:45 2005 @@ -49,7 +49,7 @@ void *dma_alloc_coherent(struct device * ret = (void *)__get_free_pages(gfp, order); if (ret != NULL) { - memset(ret, 0, size); + memset(ret, 0, PAGE_ALIGN(size)); *dma_handle = virt_to_phys(ret); } return ret; diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x '*.orig' -x '*.rej' -r orig/include/asm-i386/dma-mapping.h linux/include/asm-i386/dma-mapping.h --- orig/include/asm-i386/dma-mapping.h Mon Apr 4 22:54:41 2005 +++ linux/include/asm-i386/dma-mapping.h Mon Apr 4 22:48:11 2005 @@ -16,6 +16,23 @@ void *dma_alloc_coherent(struct device * void dma_free_coherent(struct device *dev, size_t size, void *vaddr, dma_addr_t dma_handle); +static inline int +dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma, + void *vaddr, dma_addr_t handle, size_t size) +{ + unsigned long offset = vma->vm_pgoff, usize; + + size = PAGE_ALIGN(size) >> PAGE_SHIFT; + usize = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; + + if (offset >= size || usize > (size - offset)) + return -ENXIO; + + return remap_pfn_range(vma, vma->vm_start, + (__pa(vaddr) >> PAGE_SHIFT) + offset, + usize << PAGE_SHIFT, vma->vm_page_prot); +} + static inline dma_addr_t dma_map_single(struct device *dev, void *ptr, size_t size, enum dma_data_direction direction)
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - 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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