Re: [Qemu-devel] [PATCH 4/5] ATAPI pass through v2: bring the new ATAPI pass throug feature

[Bique Alexandre <alexandre.bique@citrix.com>]

On Sunday 05 July 2009 09:15:33 Christoph Hellwig wrote:
> On Wed, Jul 01, 2009 at 07:32:09PM +0100, Bique Alexandre wrote:
> > This patch brings the new ATAPI pass through 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.

In the beginning I was using bsg, so it was not a classical device on which 
you read/write/etc... It's useful there:

@@ -2856,8 +2921,16 @@ static void ide_init2(IDEState *ide_state,
 
             if (bdrv_get_type_hint(s->bs) == BDRV_TYPE_CDROM) {
                 s->is_cdrom = 1;
+                s->atapi_cmd = ide_atapi_cmd;
 		bdrv_set_change_cb(s->bs, cdrom_change_cb, s);
             }
+#if CONFIG_ATAPI_PT
+            else if (bdrv_get_type_hint(s->bs) == BDRV_TYPE_CDROM_PT) {
+                s->is_cdrom = 1;
+                s->atapi_cmd = ide_atapi_pt_cmd;
+                bdrv_set_change_cb(s->bs, cdrom_change_cb, s);
+            }
+#endif /* CONFIG_ATAPI_PT */
         }
         s->drive_serial = drive_serial++;
         strncpy(s->drive_serial_str, drive_get_serial(s->bs),

So I need a flag somewhere to initialize IDEState as a CD-ROM pass through. 
Even if the emulation code and the pass through code uses the same device, 
they don't use it the same way:
 - read/write/seek/... (emulation)
 - ioctl (pass through)

I think that it's good to keep a way to use the emulation code over the CD-ROM 
device.

I'll look at a better way to do this. If you have any suggestion ? :-)

Thanks Christoph.

-- 
Alexandre Bique