checking for resume= cmdline with hybrid suspend hibernate

[lists@xxxxxxxxxxxxxxxxx (Chris Murphy)]

I'm seeing this on a Fedora 28 system with systemd-238-8.git0e0aa59.fc28.x86_64

Jun 02 15:11:33 f28h.local systemd[1]: Starting Hybrid Suspend+Hibernate...

[chris at f28h ~]$ sudo cat /proc/cmdline

BOOT_IMAGE=/root28/boot/vmlinuz-4.17.0-0.rc7.git1.1.fc29.x86_64
root=UUID=2662057f-e6c7-47fa-8af9-ad933a22f6ec ro
rootflags=subvol=root28 rhgb quiet rd.luks=0 rd.lvm=0 rd.md=0 rd.dm=0
enable_mtrr_cleanup=1 zswap.enabled=1 zswap.max_pool_percent=25
zswap.compressor=lz4 LANG=en_US.UTF-8 no_console_suspend


There is no resume= for the kernel to find the resulting hibernation
image (and I'm going to set aside that I'm pretty sure when Secure
Boot is enabled, that Fedora's kernels don't even support restoring
hibernation images). At one time I thought systemd had a check to see
if the cmdline contained a resume hint for the kernel to find the
hibernation image, and wouldn't do any variant of hibernation if that
hint is not present. But I guess not?

I'm pretty sure it's the DE that's asking for hybrid suspend+hibernate
but I don't know whose domain it is to check if hibernate is actually
supported. I'm vaguely aware of CanHibernate() but I don't know what
all is included in that test.

Thanks,

-- 
Chris Murphy