Re: [Qemu-devel] cdrom disc type - is this patch correct? (unbreaks recent FreeBSD guest's -cdrom access)

[Jens Axboe]

On Tue, Nov 13 2007, Juergen Lock wrote:
> Hi!
> 
>  Yesterday I learned that FreeBSD 7.0-BETA2 guests will no longer
> read from the emulated cd drive, apparently because of this commit:
>       
> http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/dev/ata/atapi-cd.c.diff?r1=1.193;r2=1.193.2.1
> The following patch file added to the qemu-devel port fixes the issue
> for me, is it also correct?   (making the guest see a dvd in the drive
> when it is inserted, previously it saw the drive as empty.)
> 
>  The second hunk is already in qemu cvs so remove it if you want to
> test on that.  ISO used for testing:
>       
> ftp://ftp.freebsd.org:/pub/FreeBSD/ISO-IMAGES-i386/7.0/7.0-BETA2-i386-disc1.iso
> (test by either selecting fixit->cdrom or by trying to install, just
> booting it will always work because that goes thru the bios.)
> 
> Index: qemu/hw/ide.c
> @@ -1339,6 +1341,8 @@
>                  case 0x2a:
>                      cpu_to_ube16(&buf[0], 28 + 6);
>                      buf[2] = 0x70;
> +                    if (bdrv_is_inserted(s->bs))
> +                        buf[2] = 0x40;

medium type code has been obsoleted since at least 1999. Looking back at
even older docs, 0x70 is 'door closed, no disc present'. 0x40 is a
reserved value though, I would not suggest using that. Given that
freebsd breaks, my suggest change would be the below - keep the 0x70 for
when no disc is really inserted, but don't set anything if there is.

diff --git a/hw/ide.c b/hw/ide.c
index 5f76c27..52d4c78 100644
--- a/hw/ide.c
+++ b/hw/ide.c
@@ -1344,7 +1344,10 @@ static void ide_atapi_cmd(IDEState *s)
                     break;
                 case 0x2a:
                     cpu_to_ube16(&buf[0], 28 + 6);
-                    buf[2] = 0x70;
+                   if (!bdrv_is_inserted(s->bs))
+                       buf[2] = 0x70;
+                   else
+                       buf[2] = 0;
                     buf[3] = 0;
                     buf[4] = 0;
                     buf[5] = 0;

-- 
Jens Axboe