Having discussed with Matthew offlist, I think we've come to the following conclusion - there's a number of drivers that buggily ignore vm_pgoff. So, what I proposed is: static int __vm_insert_range(struct vm_struct *vma, struct page *pages, size_t num, unsigned long offset) { unsigned long count = vma_pages(vma); unsigned long uaddr = vma->vm_start; int ret; /* Fail if the user requested offset is beyond the end of the object */ if (offset > num) return -ENXIO; /* Fail if the user requested size exceeds available object size */ if (count > num - offset) return -ENXIO; /* Never exceed the number of pages that the user requested */ for (i = 0; i < count; i++) { ret = vm_insert_page(vma, uaddr, pages[offset + i]); if (ret < 0) return ret; uaddr += PAGE_SIZE; } return 0; } /* * Maps an object consisting of `num' `pages', catering for the user's * requested vm_pgoff */ int vm_insert_range(struct vm_struct *vma, struct page *pages, size_t num) { return __vm_insert_range(vma, pages, num, vma->vm_pgoff); } /* * Maps a set of pages, always starting at page[0] */ int vm_insert_range_buggy(struct vm_struct *vma, struct page *pages, size_t num) { return __vm_insert_range(vma, pages, num, 0); } With this, drivers such as iommu/dma-iommu.c can be converted thusly: int iommu_dma_mmap(struct page **pages, size_t size, struct vm_area_struct *vma+) { - unsigned long uaddr = vma->vm_start; - unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT; - int ret = -ENXIO; - - for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) { - ret = vm_insert_page(vma, uaddr, pages[i]); - if (ret) - break; - uaddr += PAGE_SIZE; - } - return ret; + return vm_insert_range(vma, pages, PAGE_ALIGN(size) >> PAGE_SHIFT); } and drivers such as firewire/core-iso.c: int fw_iso_buffer_map_vma(struct fw_iso_buffer *buffer, struct vm_area_struct *vma) { - unsigned long uaddr; - int i, err; - - uaddr = vma->vm_start; - for (i = 0; i < buffer->page_count; i++) { - err = vm_insert_page(vma, uaddr, buffer->pages[i]); - if (err) - return err; - - uaddr += PAGE_SIZE; - } - - return 0; + return vm_insert_range_buggy(vma, buffer->pages, buffer->page_count); } and this gives us something to grep for to find these buggy drivers. Now, this may not look exactly equivalent, but if you look at fw_device_op_mmap(), buffer->page_count is basically vma_pages(vma) at this point, which means this should be equivalent. We _could_ then at a later date "fix" these drivers to behave according to the normal vm_pgoff offsetting simply by removing the _buggy suffix on the function name... and if that causes regressions, it gives us an easy way to revert (as long as vm_insert_range_buggy() remains available.) In the case of firewire/core-iso.c, it currently ignores the mmap offset entirely, so making the above suggested change would be tantamount to causing it to return -ENXIO for any non-zero mmap offset. IMHO, this approach is way simpler, and easier to get it correct at each call site, rather than the current approach which seems to be error-prone. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up