Re: [Qemu-block] [PATCH v2 1/6] block/qdev: Allow node name for drive properties

[Max Reitz]

On 30.06.2016 16:13, Kevin Wolf wrote:
> If a node name instead of a BlockBackend name is specified as the driver
> for a guest device, an anonymous BlockBackend is created now.
> 
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  hw/core/qdev-properties-system.c | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)

I just noticed this won't work with (at least) USB mass storage devices.
scsi_bus_legacy_add_drive() creates a new device and uses
qdev_prop_set_drive() to set its drive, and that function uses
blk_name() to get the required value for .drive.

That can of course be fixed by using bdrv_get_node_name(blk_bs(value))
there if blk_name(value) is empty. But in addition we need to make sure
that the BB is not deleted in usb_msd_realize_storage() (because that
function has to detach the device from the BB before creating the SCSI
disk), so we need to wrap the explicitly hacky block there in
blk_ref(blk) and blk_unref(blk).

Max

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