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. -- Måns Rullgård mans@xxxxxxxxx
