Dear folks,
I have a basic question, in __dma_alloc_buffer function (arch/arm/mm/dma-mapping.c, v3.3)
u64 mask = get_coherent_dma_mask(dev);
if (!mask)
return NULL;
if (mask < 0xffffffffULL)
gfp |= GFP_DMA;
page = alloc_pages(gfp, order);
if (!page)
return NULL;
...
what does the second if statement mean?
(I'm accessing this function to get memory for DMA. then should I have coherent_dma_mask < 0xffffffff ? if so, what does it mean? )
Thanks,
Chan
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