[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 4/5] ATAPI pass through v2: bring the new ATAPI
Re: [Qemu-devel] [PATCH 4/5] ATAPI pass through v2: bring the new ATAPI pass throug feature
Tue, 7 Jul 2009 13:45:50 +0100
Christoph Hellwig writes ("Re: [Qemu-devel] [PATCH 4/5] ATAPI pass through v2:
bring the new ATAPI pass throug feature"):
> I really don't understand the need for the BDRV_TYPE_CDROM_PT block
> device type. The use of BDRV_TYPE_* is mostly a hint for ide/scsi
> what kind of device where dealing with, and a passthrough CDROM should
> be different from a real one. I think we should just make any drive
> that points to a hardware CDROM device use the passthrough code, similar
> to how you'll get a hardware passthrough SCSI CDROM if you point the
> -drive option to a /dev/sr* device for a host CDROM.
I'm afraid I don't really understand this. There is no SCSI
passthrough for cdroms as far as I can see, other than if you ask to
do generic scsi passthrough.
That is, cdroms exposed to the guest configured via the -drive option
via an emulated scsi controller seem only support ordinary data
read/write, via the ordinary block read/write functions in
scsi-disk.c. I couldn't find an ability to take general cdrom SCSI
commands and pass through to the host's SCSI layer other than in
scsi-generic.c; those functions seem to not be called conditionally as
far as I can see.
Perhaps you could point out to me the bit I'm missing ?