> (Not to mention the > fact that in any particular case we never need both pre- and post- > notifications.) For voltage and frequency scaling in embedded devices we defiantly have used both pre and post notifications. Tell drivers to 'prepare' for change. This in some cases means suspending master peripheral DMA operations to DDR. Next the power manager does the DVFS switch. Finally a "post" notification is sent which allows master drivers to resume their DMA accesses. Some devices are part of smarter busses which have some notion of these. Others don't. In general you provide the list entries in the generic structure. Whether a specific device registers a local call back is something else all together. Regards, Richard W.
