On Mon, Dec 05, 2011 at 01:18:30PM -0500, Nicolas Pitre wrote: > On Mon, 5 Dec 2011, Dave Martin wrote: > > > On Mon, Dec 05, 2011 at 12:40:16PM -0500, Nicolas Pitre wrote: > > > On Mon, 5 Dec 2011, Dave Martin wrote: > > > > On Sat, Dec 03, 2011 at 10:12:53AM +1100, Benjamin Herrenschmidt wrote: > > > > > On Fri, 2011-12-02 at 11:28 -0800, Linus Torvalds wrote: > > > > > > Don't *change* NO_IRQ to zero (that whole #define is broken - leave it > > > > > > around as a marker of brokenness), just start removing it from all the > > > > > > ARM drivers that use the OF infrastructure. Which is presumably not > > > > > > all that many yet. > > > > > > > > > > > > So whenever you find breakage, the fix now is to just remove NO_IRQ > > > > > > tests, and replace them with "!irq". > > > > > > > > > > > > > Russell, do you know whether it would make sense to set a timeline for > > > > removing NO_IRQ from ARM platforms and migrating to 0 for the no-interrupt > > > > case? I'm assuming that this mainly involves migrating existing hard-wired > > > > code that deals with interrupt numbers to use irq domains. > > > > > > How many drivers do use IRQ #0 to start with? We might discover that in > > > practice there is only a very few cases where this is an issue if 0 > > > would mean no IRQ. > > > > The total number of files referring to NO_IRQ is not that huge: > > > > arch/arm/ 188 matches in 39 files > > drivers/ 174 matches in 84 files > > > > Unfortunately, NO_IRQ is often not spelled "NO_IRQ". It looks like the assumption > > "irq < 0 === no irq" may be quite a lot more widespread than "NO_IRQ === no irq". > > Since there's no specific thing we can grep for (and simply due to volume) > > finding all such instances may be quite a bit harder. > [...] > > ARgh. > > My point was about current actual usage of the IRQ numbered 0 which > probably prompted the introduction of NO_IRQ in the first place. What I > was saying is that the number of occurrences where IRQ #0 is currently > used into drivers that would get confused if 0 would mean no IRQ is > probably quite small. Ah, I misunderstood -- that's a separate issue, but also an important one. I guess this applies to a fair number of older boards. One way of fixing this would be to migrate those boards to use irq domains -- but those boards may be sporadically maintained. > But as you illustrated, there is a large number of drivers that already > assume no IRQ is < 0, even if they don't use any IRQ #0 themselves. > That is a much bigger problem to fix. My concern is that as soon as we start to change this in significant volume, a _lot_ of stuff is going to break. Everywhere that an irq value is passed from one piece of code to another, there is a potential interface mismatch -- there seems to be no single place where we can apply a conversion and fix everything. Cheers ---Dave -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
