On Mon, 23 Apr 2007, James Bottomley wrote: > 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);
Ok, version 3, small, and hopefully, beautiful: dma_declare_coherent_memory() allocates a bitmap 1 bit per page, it calculates the bitmap size based on size of long, but allocates bytes... Thanks to James Bottomley for clarifications and corrections. Signed-off-by: G. Liakhovetski <[EMAIL PROTECTED]> diff --git a/arch/cris/arch-v32/drivers/pci/dma.c b/arch/cris/arch-v32/drivers/pci/dma.c index 70d3bf0..832fc63 100644 --- a/arch/cris/arch-v32/drivers/pci/dma.c +++ b/arch/cris/arch-v32/drivers/pci/dma.c @@ -76,7 +76,7 @@ int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr, { void __iomem *mem_base; int pages = size >> PAGE_SHIFT; - int bitmap_size = (pages + 31)/32; + int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long); if ((flags & (DMA_MEMORY_MAP | DMA_MEMORY_IO)) == 0) goto out; diff --git a/arch/i386/kernel/pci-dma.c b/arch/i386/kernel/pci-dma.c index 3ebcea0..30b754f 100644 --- a/arch/i386/kernel/pci-dma.c +++ b/arch/i386/kernel/pci-dma.c @@ -77,7 +77,7 @@ int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr, { void __iomem *mem_base = NULL; int pages = size >> PAGE_SHIFT; - int bitmap_size = (pages + 31)/32; + int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long); if ((flags & (DMA_MEMORY_MAP | DMA_MEMORY_IO)) == 0) goto out; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/