Jean Delvare said the following: > Hi Michael, > > On Fri, 17 Dec 2010 13:09:54 +0100, Michael Lawnick wrote: >> Sorry to disturb, but >> <MANTRA> >> Disabling interrupts may be done only for a few instructions.</MANTRA> >> >> Even 1 us is an eternity on modern systems. > > Don't be sorry, this is exactly the kind of input I was asking for. I'm > a little surprised, I thought disabling interrupts for a couple > microseconds was happening all the time, but I'll trust your > experience. I can't tell whether this is happening all the time, but I can imagine and I highly discourage this. This is IMHO one of the lessons many LINUX developers have still to learn. Maybe it's a history reason. > Given your point and Ben's, it seems clear that my patch is > not acceptable as is, and at the very least I should make the spinlock > usage optional. At last you might not come around your solution, but a H/W-S/W combination driving you in such a direction should be considered broken. Using it in professional environment needs heavy discussions about pros and cons, best would be to beat the H/W designers to provide a real controller. Of course it may be used in a case, where you simply need a (temporary) hack to get something working. -- KR Michael -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
