• Linus Torvalds's avatar
    vm: add vm_iomap_memory() helper function · b4cbb197
    Linus Torvalds authored
    Various drivers end up replicating the code to mmap() their memory
    buffers into user space, and our core memory remapping function may be
    very flexible but it is unnecessarily complicated for the common cases
    to use.
    
    Our internal VM uses pfn's ("page frame numbers") which simplifies
    things for the VM, and allows us to pass physical addresses around in a
    denser and more efficient format than passing a "phys_addr_t" around,
    and having to shift it up and down by the page size.  But it just means
    that drivers end up doing that shifting instead at the interface level.
    
    It also means that drivers end up mucking around with internal VM things
    like the vma details (vm_pgoff, vm_start/end) way more than they really
    need to.
    
    So this just exports a function to map a certain physical memory range
    into user space (using a phys_addr_t based interface that is much more
    natural for a driver) and hides all the complexity from the driver.
    Some drivers will still end up tweaking the vm_page_prot details for
    things like prefetching or cacheability etc, but that's actually
    relevant to the driver, rather than caring about what the page offset of
    the mapping is into the particular IO memory region.
    Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    b4cbb197
memory.c 116 KB