On Jun 25, 2015, at 11:14 AM, Programmingkid wrote: > > On Jun 25, 2015, at 2:53 AM, Markus Armbruster wrote: > >> Programmingkid <programmingk...@gmail.com> writes: >> >>> 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. >> >> What about /dev/sr0, /dev/sr1, and whatever other names could refer to a >> block device without a medium? >> >> Comparing filenames isn't a good way to test "is a block device without >> a medium". > > I think we are going to have to agree to disagree. I have never used the > /dev/sr(0 | 1) devices and don't see how they would be effected by this > patch. Are you trying to say the /dev/sr(0 | 1) devices *should* be handled > by this patch?
Thinking about your question some more, I see what you mean. On Linux /dev/sr0 refers to the cdrom drive. Also on Linux, the /dev/cdrom link refers to the /dev/sr0 device file. So if you just use /dev/cdrom, you are good.