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    Subjectquestion on char driver mmap

    I have a need for a device driver to map a page of memory between interrupt
    handlers and userspace. It's been suggested that I use something like the
    following code (simplified):

    unsigned long mypage;

    int my_mmap(struct file *filp, struct vm_area_struct *vma)
    unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;

    if (offset & ~PAGE_MASK)
    return -ENXIO;

    mypage = __get_free_page(GFP_KERNEL);
    remap_page_range(vma->vm_start, virt_to_phys((void *) mypage),
    PAGE_SIZE, vma->vm_page_prot);
    return 0;

    This seems to work. If I do this, however, do I need to hook into the munmap()
    file operations to handle unmapping, clearing the reserved bit, and freeing the
    page, or will the memory subsystem do it for me?


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      Last update: 2005-03-22 14:05    [W:0.036 / U:14.668 seconds]
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