Hi, according to the source code, the option parser for -a tries to resolve a symlink using a function disk_name(), the result is something like sda, sdb sdc. This function requires the full pathname including /dev. The code handling the spindown timer then uses this short name (sda, sdb, sdc) for further action.
The code handling the -t option does not use that disk_name() function, but always puts a "/dev/" before the supplied disk name. This is why you get the "/dev//dev/disk/by-id/ata-... does not exist" error. So yes, this is indeed inconsistent and confusing. Furthermore, the device name lookup for -a does not report any errors when the device is not found.
