Documentation/power/userland-swsusp.rst

25 reading, it is considered to be in the suspend mode.  Otherwise it is
26 assumed to be in the resume mode.  The device cannot be open for simultaneous
71 	return the actual size of the hibernation image
96 	swap files (see Documentation/power/swsusp-and-swap-files.rst for
100 	enable/disable the hibernation platform support,
104 	make the kernel transition the system to the hibernation
109 	immediately enter the suspend-to-RAM state, so this call must always
112 	is needed to implement the suspend-to-both mechanism in which the
121 - you cannot read() more than one virtual memory page at a time
122 - read()s across page boundaries are impossible (ie. if you read() 1/2 of
156 SNAPSHOT_ATOMIC_RESTORE will not succeed.  Still, this is not a fool-proof