On Thu, May 07, 2009 at 05:40:15PM +0800, Sheng Yang wrote: > It's indeed weird. Why the semantic of pci_enable_msix can be changed to > "enable msix, or tell me how many vector do you have"? You can simply call > pci_msix_table_size() to get what you want, also without any more work, no? I > can't understand... Here's a good example. Let's suppose you have a driver which supports two different models of cards, one has 16 MSI-X interrupts, the other has 10. You can call pci_enable_msix() asking for 16 vectors. If your card is model A, you get 16 interrupts. If your card is model B, it says "you can have 10". This is less work in the driver (since it must implement falling back to a smaller number of interrupts *anyway*) than interrogating the card to find out how many interrupts there are, then requesting the right number, and still having the fallback path which is going to be less tested. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
