Is there some reason why this feature needs to be enabled by an 
ioctl?  Why not make this suspend blocker permanently enabled?

Alan Stern

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The ioctl is there so that user space can use suspend blockers, which is
needed because only user space know that some activities are going to continue
and therefore the system should not be suspended (like playing music "in the
background").

From all of the interfaces that could be used for this purpose ioctl appears to
be the most convenient (we need something that is per process and allows us
to carry out four operations: creat, destroy, activate, deactivate).

Rafael
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