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    SubjectRe: [PATCH] dma_declare_coherent_memory wrong allocation
    On Mon, 2007-04-23 at 00:45 +0200, Guennadi Liakhovetski wrote:
    > Right, thinko. How about using his:
    > + int pages = DIV_ROUND_UP(size, PAGE_SIZE);

    Actually, no ... this has to be size >> PAGE_SHIFT. The reason being
    that the allocator is designed to allocate pages out of a device memory
    buffer. If the size isn't a multiple of page size, we have to round
    down (we can't allocate the last page if the memory we have is only part
    of a page).

    I suppose if you want to catch the unlikely nutcase where size <
    PAGE_SIZE you could

    if (unlikely(pages == 0))
    goto out;

    > + int bitmap_size = BITS_TO_LONGS(pages) * BYTES_PER_LONG;

    This is fine, except the BYTES_PER_LONG. Traditionally, we do this with
    sizeof(long). The only reason to have a #define for it is if it has to
    be used in a macro (the compiler does sizeof() not the preprocessor).

    How about just a simple

    int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);


    Then you don't need the first patch defining BYTES_PER_LONG.

    > to also allow for size not an integer number of pages as Andrew noticed?
    > This could be done in 2 patches:


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      Last update: 2007-04-23 18:53    [W:0.020 / U:1.992 seconds]
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