[lkml]   [2009]   [Sep]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH] NOMMU: Fix MAP_PRIVATE mmap() of objects where the data can be mapped directly
    On Fri, Sep 25, 2009 at 4:24 PM, David Howells <> wrote:
    > graff yang <> wrote:
    >> > +       if (capabilities & BDI_CAP_MAP_DIRECT) {
    >> This will breaks many drivers, e.g. some frame-buffer drivers, on NOMMU
    >> system.  Because they don't have get_unmapped_area().  These drivers depend
    >> on it's mmap() to return the frame-buffer base address.
    > Then they won't work on NOMMU.  Read Documentation/nommu-mmap.txt:
    >        ============================================
    >        ============================================
    >        To provide shareable character device support, a driver must provide a
    >        file->f_op->get_unmapped_area() operation. The mmap() routines will
    >        call this to get a proposed address for the mapping. This may return an
    >        error if it doesn't wish to honour the mapping because it's too long,
    >        at a weird offset, under some unsupported combination of flags or
    >        whatever.
    > The chardev driver doesn't provide the virtual address through its mmap() fop
    > in MMU-mode either - that's provided by do_mmap_pgoff().
    > David
    OK, I think do_mmap_pgoff() now looks nice with your patch. Merely,
    at least the alsa/fb driver
    will crash due to the vm_region changes.
    The alsa guys are fixing this issue:

    Is there any other things be affected?

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2009-09-25 13:07    [W:0.021 / U:20.760 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site