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From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] hw/ppc/spapr: Fix boot path of usb-host
 storage devices
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To: Thomas Huth <thuth@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>, qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, qemu-ppc@nongnu.org

  Hi,

> That's true for the default case, but for the pseries machine, there is
> already code that changes the boot path for virtual usb-storage devices,
> see the function spapr_get_fw_dev_path() :
>=20
>         ... else if (usb) {
>             /*
>              * We use SRP luns of the form 01000000 | (usb-port << 16) | =
lun
>              * in the top 32 bits of the 64-bit LUN
>              */
>             unsigned usb_port =3D atoi(usb->port->path);
>             unsigned id =3D 0x1000000 | (usb_port << 16) | d->lun;
>             return g_strdup_printf("%s@%"PRIX64, qdev_fw_name(dev),
>                                    (uint64_t)id << 32);
>         }

Hmm, I thought the point of using standard open firmware paths was that
we don't need hacks like this.  Looks like things are not *that*
standardized then if some archs need extra tweaks ...

But if that is needed for pseries *anyway* it doesn't hurt to do the
same for usb-host.

> > If usb-host (and usb-redir too btw) create paths identical to the ones
> > created by usb-storage.  Existing firmware should cope just fine
> > (assuming bootindex for usb-storage works).
>=20
> Which firmware can deal with these original device paths with "channel@0"
> in it? Certainly not SLOF. Maybe OpenBIOS? Does OpenBIOS support USB stor=
age
> devices?

seabios does, and I expect ovmf too (didn't test though).

cheers,
  Gerd