Messages in this thread | | | From | "David S. Miller" <> | Date | Fri, 9 Mar 2001 12:07:04 -0800 (PST) | Subject | Re: [linux-usb-devel] Re: SLAB vs. pci_alloc_xxx in usb-uhci patch [RFC: API] |
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David Brownell writes: > Given that some hardware must return the dma addresses, why > should it be a good thing to have an API that doesn't expose > the notion of a reverse mapping? At this level -- not the lower > level code touching hardware PTEs.
Because its' _very_ expensive on certain machines. You have to do 1 or more I/O accesses to get at the PTEs.
If you add this reverse notion to just one API (the dma pool one) then people will complain (rightly) that there is not orthogonality in the API since the other mapping functions do not provide it.
No, it is unacceptable.
Later, David S. Miller davem@redhat.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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