On Sat, Oct 10, 2015 at 12:48:22AM +0100, Måns Rullgård wrote: > Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> writes: > > > On Fri, Oct 09, 2015 at 10:57:35PM +0100, Mans Rullgard wrote: > >> This passes a data pointer specified in the sched_clock_register() > >> call to the read callback allowing simpler implementations thereof. > >> > >> In this patch, existing uses of this interface are simply updated > >> with a null pointer. > > > > This is a bad description. It tells us what the patch is doing, > > (which we can see by reading the patch) but not _why_. Please include > > information on why the change is necessary - describe what you are > > trying to achieve. > > Currently most of the callbacks use a global variable to store the > address of a counter register. This has several downsides: > > - Loading the address of a global variable can be more expensive than > keeping a pointer next to the function pointer. > > - It makes it impossible to have multiple instances of a driver call > sched_clock_register() since the caller can't know which clock will > win in the end. > > - Many of the existing callbacks are practically identical and could be > replaced with a common generic function if it had a pointer argument. > > If I've missed something that makes this a stupid idea, please tell. So my next question is whether you intend to pass an iomem pointer through this, or a some kind of structure, or both. It matters, because iomem pointers have a __iomem attribute to keep sparse happy. Having to force that attribute on and off pointers is frowned upon, as it defeats the purpose of the sparse static checker. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
