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Re: [Qemu-devel] [PATCH 26/30] usb-storage: make its storage SCSI bus ho
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH 26/30] usb-storage: make its storage SCSI bus hotpluggable explicitly |
Date: |
Wed, 24 Sep 2014 17:22:24 +0200 |
On Wed, 24 Sep 2014 14:50:41 +0200
Gerd Hoffmann <address@hidden> 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
>
>
- [Qemu-devel] [PATCH 25/30] usb-bot: drop not needed "allow_hotplug = 0", (continued)
[Qemu-devel] [PATCH 26/30] usb-storage: make its storage SCSI bus hotpluggable explicitly, Igor Mammedov, 2014/09/24
[Qemu-devel] [PATCH 30/30] qdev: HotplugHandler: add support for unplugging BUS-less devices, Igor Mammedov, 2014/09/24
[Qemu-devel] [PATCH 16/30] virtio-serial: convert to hotplug-handler API, Igor Mammedov, 2014/09/24
[Qemu-devel] [PATCH 27/30] usb-storage: drop not needed "allow_hotplug = 0", Igor Mammedov, 2014/09/24
[Qemu-devel] [PATCH 28/30] usb: convert to hotplug handler API, Igor Mammedov, 2014/09/24