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From: Thomas Huth <thuth@redhat.com>
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Date: Thu, 19 Jul 2018 10:10:52 +0200
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Subject: Re: [Qemu-devel] How to generate custom fw paths for IDE devices?
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To: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, qemu-devel <qemu-devel@nongnu.org>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, Laszlo Ersek <lersek@redhat.com>, armbru@redhat.com, marcel@redhat.com, jsnow@redhat.com, "qemu-ppc@nongnu.org" <qemu-ppc@nongnu.org>

On 18.07.2018 23:13, Mark Cave-Ayland wrote:
> Hi all,
>=20
> Following on from a couple of patches I've previously posted to the
> mailing list at
> https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg08836.html I'v=
e
> made some good progress with trying to add bootindex support to OpenBIO=
S
> but I'm stuck with generating the IDE device paths from QEMU.
>=20
> According to OpenBIOS the device path for a cdrom on a sun4u machine
> should be:
>=20
> =C2=A0 /pci@1fe,0/pci@1,1/ide@3/ide1@8100/cdrom@0
>=20
> whereas with my working patchset I'm currently generating:
>=20
> =C2=A0 /pci@1fe,0/pci@1,1/ide@3/drive@1
>=20
> The issue is that the drive@1 part is being generated by the IDE drive
> device attached to the IDE bus in hw/ide/qdev.c, and so I think I need
> to override idebus_get_fw_dev_path() to manually generate the remainder
> of the path including both the controller and the correctly named drive
> node.
>=20
> One option may be to consider subclassing IDEBus and overriding
> idebus_get_fw_dev_path() there, but the cmd646 device is a child of
> TYPE_PCI_IDE which has its own internal IDEBus and so it seems
> overriding it is impossible.
>=20
> Can anyone point me in the right direction as to how to generate the
> correct fw path for IDE devices in the above format for sun4u machines?

Not sure if it is of any help, but the pseries machine is also rewriting
the device paths for the device tree: See function spapr_get_fw_dev_path
in hw/ppc/spapr.c.

 Thomas