On Wed, 24 Sep 2014 14:50:41 +0200 Gerd Hoffmann <kra...@redhat.com> wrote:
> On Mi, 2014-09-24 at 11:48 +0000, Igor Mammedov wrote: > > usb-storage uses SCSI bus to provide underling storage > > (i.e. scsi-disk) and it's hotpluggable. > > No. usb-storage itself (the scsi hba) is hotpluggable, but the scsi > devices connected are not. Agree, I'm sorry for my bad English, under "it's hotpluggable" I've meant usb-storage. > > On the qemu side it isn't a problem, but the protocol has constrains. > First there is no way to signal devices coming and going, so the guest > wouldn't see them until reboot (or manual driver reload). Second for > multi-lun devices only the number of luns is reported and devices are > expected to have luns 0 .. $count-1. So with three devices connected > and the second being hot-unplugged you end up with an illegal > configuration. > > Therefore device initialization (IIRC) goes like this today: > > (1) add hba (i.e. usb-storage). > (2) add scsi device. > (3) turn off hotplug on the scsi bus. > (4) make the whole thing visible to the guest (usb_attach_device). > > cheers, > Gerd > >
