On Jun 23, 2015, at 2:06 PM, John Snow wrote: > > > On 06/23/2015 01:56 PM, Programmingkid wrote: >> Fix real cdrom detection so that a real cdrom can actually be used. >> >> signed-off-by: John Arbuckle <programmingk...@gmail.com >> <mailto:programmingk...@gmail.com>> >> >> This patch has been tested on Mac OS X host and guest. >> Command used: qemu-system-ppc -cdrom /dev/cdrom >> >> Note: I was able to view the files using OpenBIOS, but not on >> Mac OS X. The size of the disc is reported correctly but some >> error happens that prevents it from mounting in Mac OS X. This >> is probably another bug with QEMU. >> >> --- >> block.c | 3 ++- >> 1 files changed, 2 insertions(+), 1 deletions(-) >> >> diff --git a/block.c b/block.c >> index dd4f58d..75ccfad 100644 >> --- a/block.c >> +++ b/block.c >> @@ -583,7 +583,8 @@ static int find_image_format(BlockDriverState *bs, >> const char *filename, >> int ret = 0; >> >> >> >> /* Return the raw BlockDriver * to scsi-generic devices or empty >> drives */ >> - if (bs->sg || !bdrv_is_inserted(bs) || bdrv_getlength(bs) == 0) { >> + if (bs->sg || !bdrv_is_inserted(bs) || bdrv_getlength(bs) == 0 >> + || strcmp("/dev/cdrom", filename) == 0) { >> *pdrv = &bdrv_raw; >> return ret; >> } >> -- >> 1.7.5.4 >> > > So what's the issue that this patch attempts to fix and how did you > determine that the fix was needed here? It doesn't look like it respects > proper abstraction at a glance.
Without the patch, QEMU would just quit when the "-cdrom /dev/cdrom" option is given. Before the patch, the bdrv_open_inherit() function would be incorrectly called. Its documentation says "Opens a disk image (raw, qcow2, vmdk, ...)" meaning only for disk image files (not for real media). This patch prevents the bdrv_open_inherit() function from ever being called. It sets the pdrv variable to the raw format. This made sense to me since a real cdrom is read in the raw format. A quick test does show the patch works. A real cdrom is successfully opened on qemu-system-i386 using a Windows XP guest.
