Hi! Just for the record... this goes out to the lkml. This discussion was internal for way too long. (for interested lkml readers, I'm sure linux-pm mailing list has public archive somewhere). On Tue 2006-09-12 02:05:26, Eugeny S. Mints wrote: > Pavel Machek wrote: > >>>>- PowerOP is only one layer (towards the bottom) in a power management > >>>>solution. > >>>>- PowerOP does *not* replace cpufreq > >>>PowerOP provides userland interface for changing processor > >>>frequency. That's bad -- duplicate interface. > >>Basically the biggest problem with cpufreq interface is that cpufreq has > >>"chose > >>predefined closest to a given frequency" functionality implemented in the > >>kernel while there is _no_ any reason to have this functionality > >>implemented in > >>the kernel if we have sysfs interface exported by PowerOP in place - you > >>just > > > >No, there is reason to keep that in kernel -- so that cpufreq > >userspace interface can be kept, and so that resulting kernel<->user > >interface is not ugly. > Cpuferq defines cpufreq_frequency_table structure in arch independent > header while it's arch dependent data structure. A lot of code is built > around this invalid basic brick and therefore is invalid: cpufreq tables, > interface with cpu freq drivers, etc. Notion of transition latency as it > defined by cpufreq is wrong because it's not a function of cpu type but > function of current and next operating point. no runtime control on > operating points set. it's always the same set of operating points for all > system cpus in smp case and no way to define different sets or track any > dependencies in case say multi core cpus. insufficient kernel<->user space > interface to handle embedded requirements and no way to extend it within > current design. Shall I continue? Why should then anyone want to keep > cpufreq userspace interface just due to keep it? Yes, please continue. I do not think we can just rip cpufreq interface out of kernel, and I do not think it is as broken as you claim it is. Ripping interface out of kernel takes years. I'm sure cpufreq_frequency_table could be moved to asm/ header if you felt strongly about that. I believe we need to fix cpufreq if it is broken for embedded cases. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
