SATA hotplug and AHCI

[David Ehrmann]

I'm trying to get real hotplugging to work.  My motherboard uses the Via 
VT8251 southbridge which, according to the whitesheet, supports SATA 
hotplugging:

http://www.via.com.tw/en/downloads/whitepapers/chipsets/southbridge/chipsets_vt8251.pdf


I set the SATA controller to the AHCI mode in my BIOS.  When I unplug 
the drive, I see

subdisk8: detached
ad8: detached

but plugging it back in, I don't see anything, and atacontrol list 
doesn't list any devices on the channel.  If I do atacontrol reinit 
ata<number>, nothing happens, but if I do atacontrol detach ata<number> 
(it fails without detaching, first) atacontrol attach ata<number>, the 
drive is recognized

ata4: [ITHREAD]
ad8: ...
Master: ...
Slace: no device present

How can I avoid all this and get the drive to be recognized 
automatically?  Can I do this with devd?  Did I do what I needed to 
correctly set up hotplugging?