Messages in this thread | | | Date | Tue, 16 Jun 2009 17:12:14 +0900 | Subject | Re: is_device_dma_capable | From | FUJITA Tomonori <> |
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On Tue, 16 Jun 2009 16:54:24 +0930 Malcom Blaney <malcolm.blaney@maptek.com.au> wrote:
> I'm using the parport_pc driver with a dma buffer, which is provided > by calling dma_alloc_coherent in arch/x86/include/asm/dma-mapping.h. > > This is no longer working for me in 2.6.29.2, the previous version I > was using is 2.6.25.10, which was fine with the same hardware. > > The problem is that the call to is_device_dma_capable returns false, > so dma_alloc_coherent returns NULL. Do I need to set the dma_mask in > the driver for this to work correctly?
You use X86_32, right?
In 2.6.25, X86_32 and X86_64 had the own dma_alloc_coherent implementations; X86_32 accepted a device having dma_mask that is not initialized however X86_64 didn't, I think.
When we merged them, we chose to prohibit a device having dma_mask that is not initialized. I'm not sure the DMA docs say this but IMO it's good to require drivers to set up dma_mask (and coherent_dma_mask) properly if the drivers want DMA.
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