[Qemu-devel] [PATCH 0/2] Guess host device type from guest device type for block devices

[Eduardo Habkost <ehabkost@redhat.com>]

This fixes the following issue:
https://bugzilla.redhat.com/show_bug.cgi?id=473154

Sometimes a CD-ROM drive path doesn't start with /dev/cdrom, causing problems
if a disk isn't inserted on the drive. With this patch, the floppy and cdrom
drivers are used if using a host block device as backend and the
virtual device type is floppy or CD-ROM.

Example:

 $ ls -l /dev/cdrom /dev/hda
 lrwxrwxrwx 1 root root    3 Jun 17 10:20 /dev/cdrom -> hda
 brw-rw---- 1 root disk 3, 0 Jun 17 10:20 /dev/hda

Before this series (CD-ROM drive with no disk):

 $ sudo qemu-system-x86_64 -cdrom /dev/cdrom
 [works]
 $ sudo qemu-system-x86_64 -cdrom /dev/hda
 qemu: could not open disk image /dev/hda

After this series (with no disk on the CD-ROM drive, too):

 $ sudo qemu-system-x86_64 -cdrom /dev/hda
 [works]

This is based on a fix from Cole Robinson, submitted here:
http://marc.info/?l=qemu-devel&m=124458617900905

There are other two points where I think the code could be improved:

- Redundant stat() calls: stat() is called at hdev_probe_device(),
  and called again on cdrom_probe_device() and floppy_probe_device()
- Duplicated cdrom driver code for Linux and FreeBSD: I don't like #ifdefs, but
  I don't like the amount of duplicated code, either.


Eduardo Habkost (2):
  Add a BlockDriverState parameter to bdrv_probe_device()
  Guess host device type from requested guest device type

 block.c           |    6 +++---
 block/raw-posix.c |   38 +++++++++++++++++++++++++++++---------
 block/raw-win32.c |    2 +-
 block_int.h       |    2 +-
 4 files changed, 34 insertions(+), 14 deletions(-)

-- 
Eduardo