Michael Chan wrote:
On Wed, 2007-05-02 at 11:29 -0400, Jeff Garzik wrote:
Michael Chan wrote:
A non-IOMMU system using 64-bit dma_addr_t will always set
CONFIG_HIGHMEM, right?
No.
May be I misunderstood the code in illegal_highdma() in net/core/dev.c
where it is checking to see if it needs to linearize the SKB when the
device does not support 64-bit DMA. I'm using similar assumptions for
the 40-bit address check in the patch.
That function is just checking for highmem pages, no more, no less.
Your question quoted far above presumes that no 64-bit systems exist
lacking IOMMUs, which is not the case. 64-bit platforms with a 64-bit
dma_addr_t will /not/ set CONFIG_HIGHMEM, regardless of IOMMU presence.
Probably you want to base your actions on some combination of
* CONFIG_64BIT
* sizeof(dma_addr_t)
* pci_set_dma_mask() for >32 bit platforms
Regards,
Jeff
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