Messages in this thread | | | Date | Fri, 10 Oct 2008 11:40:56 +0900 | Subject | Re: [PATCH] pci: print out DMA mask info | From | FUJITA Tomonori <> |
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On Thu, 09 Oct 2008 16:05:57 -0700 Yinghai Lu <yinghai@kernel.org> wrote:
> Grant Grundler wrote: > > On Thu, Oct 09, 2008 at 02:51:32PM -0700, Yinghai Lu wrote: > >> On Thu, Oct 9, 2008 at 2:35 PM, Matthew Wilcox <matthew@wil.cx> wrote: > >>> Why's that interesting to the sysadmin of the machine? To the driver > >>> writer, certainly. But what's the use of it to the people using the > >>> machine? > > ... > >> make linux kernel act like black box as other os? > > > > I don't understand your reply. > > If someone thinks linux is a black box, printing this message won't help them. > > > could find out easily why some driver doesn't set dma mask correctly. > like why > qlogic qla2xxx only set consistent to 64bit, > emulex lpfc not set consistent to 64bit
IIRC, except for one SGI architecture, coherent_dma_mask is meaningless, dma_mask is always equal to coherent_dma_mask. Lots of IOMMU implementations ignore coherent_dma_mask and use dma_mask for alloc_coherent(). Some drivers doesn't set up coherent_dma_mask.
Theoretically, we need to fix this but it doesn't cause any problem. That's why nobody cares about it, I guess.
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