Locking in the clk API

[Jeremy Kerr]

Hi Paul,

> Again, you are approaching it from the angle that an atomic clock is a
> special requirement rather than the default behaviour.

I'm not considering it a special requirement, but it's still a requirement 
(that the called function does not sleep).

The problem with the inverse logic (clk_enable/clk_enable_sleepable) is that 
now you've made the caller need to know what kind of clock it has, or might 
have one day.

 * For clk_enable/clk_enable_atomic, the decision is: is this call in an
   atomic context?

 * For clk_enable/clk_enable_sleepable, the decision is: might the clock code
   have given us a sleeping clock?

Note that it's much easier to guarantee correctness for the first than it is 
for the second.

Cheers,


Jeremy