Hello Hiroshi, David, On Thu, 17 Apr 2008, David Brownell wrote: > On Thursday 17 April 2008, Hiroshi DOYU wrote: > > > And if there will be a little possibility that sysfs attribute can be > > used by userland in the future, keeping sysfs instead of debugfs > > doesn't seem not so illegal, does it? True, but if we can do a debugfs implementation first, then that seems like a good way to start, no? Userspace PM implementations are probably some months in the future, and we can mandate that debugfs be mounted for those. > I happen to think that the clock tree is sensitive enough > that it should not be managed from userspace in production > systems. (Except possibly through driver-specific APIs which > ensure the right rules are followed.) Too easy to break things > otherwise. In terms of the clock tree, it would be good to allow userspace-driven OPP changes, analogous to CPUFreq's userspace governor. [ In general, I agree that userspace should not be changing driver clocks directly, just like userspace should not be mucking around in /dev/mem directly :-) ] Clock tree changes (like OPP changes) which are not initiated by drivers do create some additional complexity. Drivers will need to be notified before and after these changes. It turns out that DSP Bridge already needs post-frequency-change notification for the DSP clock - there is a patch here which will soon be posted to add those. Pre-change notifiers are also needed to quiesce DMA, etc.; those are somewhat more difficult, but also in the works. - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
