Description of problem:
With 2 --disk option and --prompt option, the --disk /dev/cdrom was ignored and was asked to input the install source. As show below:
 
#virt-install -r 1024 --name rhel55_i386 --disk path=/var/lib/libvirt/images/sss.img,size=8 --disk /dev/cdrom,device=cdrom,cache=writethrough --os-variant=rhel5.4 --prompt --debug
Tue, 20 Jul 2010 20:46:21 DEBUG    Launched with command line:
/usr/sbin/virt-install -r 1024 --name rhel55_i386 --disk path=/var/lib/libvirt/images/sss.img,size=8 --disk /dev/cdrom,device=cdrom,cache=writethrough --os-variant=rhel5.4 --prompt --debug
Tue, 20 Jul 2010 20:46:21 DEBUG    Requesting libvirt URI default
Tue, 20 Jul 2010 20:46:21 DEBUG    Received libvirt URI qemu:///system
Tue, 20 Jul 2010 20:46:21 DEBUG    Requesting virt method 'hvm', hv type 'default'.
Tue, 20 Jul 2010 20:46:21 DEBUG    Received virt method 'hvm'
Tue, 20 Jul 2010 20:46:21 DEBUG    Hypervisor name is 'kvm'
Tue, 20 Jul 2010 20:46:21 DEBUG    parse_disk: returning {'format': None, 'bus': None, 'readOnly': False, 'volInstall': None, 'path': '/var/lib/libvirt/images/sss.img', 'device': 'disk', 'volName': None, 'conn': <libvirt.virConnect instance at 0x15ea830>, 'size': 8.0, 'driverCache': None, 'shareable': False, 'sparse': True}
Tue, 20 Jul 2010 20:46:21 DEBUG    Path '/var/lib/libvirt/images' is target for pool 'default'. Creating volume 'sss.img'.
Tue, 20 Jul 2010 20:46:21 DEBUG    parse_disk: returning {'format': None, 'bus': None, 'readOnly': False, 'volInstall': None, 'path': '/dev/cdrom', 'device': 'cdrom', 'volName': None, 'conn': <libvirt.virConnect instance at 0x15ea830>, 'size': None, 'driverCache': 'writethrough', 'shareable': False, 'sparse': True}
Tue, 20 Jul 2010 20:46:21 DEBUG    DISPLAY is set: graphics defaulting to VNC.
Tue, 20 Jul 2010 20:46:22 DEBUG    Setting os type to 'linux' for variant 'rhel5.4'
What is the install CD-ROM/ISO or URL? 


With out the --prompt option, the install is ok. As show below:


# virt-install -r 1024 --name rhel55_i386 --disk path=/var/lib/libvirt/images/sss.img,size=8 --disk /dev/cdrom,device=cdrom,cache=writethrough --os-variant=rhel5.4 --debugTue, 20 Jul 2010 18:34:42 DEBUG    Launched with command line:
/usr/sbin/virt-install -r 1024 --name rhel55_i386 --disk path=/var/lib/libvirt/images/sss.img,size=8 --disk /dev/cdrom,device=cdrom,cache=writethrough --os-variant=rhel5.4 --debug
Tue, 20 Jul 2010 18:34:42 DEBUG    Requesting libvirt URI default
Tue, 20 Jul 2010 18:34:43 DEBUG    Received libvirt URI qemu:///system
Tue, 20 Jul 2010 18:34:43 DEBUG    Requesting virt method 'default', hv type 'default'.
Tue, 20 Jul 2010 18:34:43 DEBUG    Received virt method 'hvm'
Tue, 20 Jul 2010 18:34:43 DEBUG    Hypervisor name is 'kvm'
Tue, 20 Jul 2010 18:34:43 DEBUG    parse_disk: returning {'format': None, 'bus': None, 'readOnly': False, 'volInstall': None, 'path': '/var/lib/libvirt/images/sss.img', 'device': 'disk', 'volName': None, 'conn': <libvirt.virConnect instance at 0x27b6830>, 'size': 8.0, 'driverCache': None, 'shareable': False, 'sparse': True}
Tue, 20 Jul 2010 18:34:43 DEBUG    Path '/var/lib/libvirt/images' is target for pool 'default'. Creating volume 'sss.img'.
Tue, 20 Jul 2010 18:34:43 DEBUG    parse_disk: returning {'format': None, 'bus': None, 'readOnly': False, 'volInstall': None, 'path': '/dev/cdrom', 'device': 'cdrom', 'volName': None, 'conn': <libvirt.virConnect instance at 0x27b6830>, 'size': None, 'driverCache': 'writethrough', 'shareable': False, 'sparse': True}
Tue, 20 Jul 2010 18:34:43 DEBUG    DISPLAY is set: graphics defaulting to VNC.
Tue, 20 Jul 2010 18:34:43 DEBUG    Setting os type to 'linux' for variant 'rhel5.4'


Starting install...
Tue, 20 Jul 2010 18:34:43 DEBUG    Creating storage volume 'sss.img' with xml:
<volume>
  <name>sss.img</name>
  <capacity>8589934592</capacity>
  <allocation>0</allocation>
  <target>
    <format type='raw'/>
  </target>
</volume>

Allocating 'sss.img'                                                       | 8.0 GB     00:00     
Tue, 20 Jul 2010 18:34:43 DEBUG    Storage volume 'sss.img' install complete.
Tue, 20 Jul 2010 18:34:43 DEBUG    Can't fix selinux context in this case.
Tue, 20 Jul 2010 18:34:43 DEBUG    Generated install XML: 
<domain type='kvm'>
  <name>rhel55_i386</name>
  <currentMemory>1048576</currentMemory>
  <memory>1048576</memory>
  <uuid>18fdf711-a5fa-8b9c-c8ca-f97475086038</uuid>
  <os>
    <type arch='x86_64'>hvm</type>
    <boot dev='cdrom'/>
  </os>
  <features>
    <acpi/><apic/><pae/>
  </features>
  <clock offset="utc"/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>destroy</on_reboot>
  <on_crash>destroy</on_crash>
  <vcpu>1</vcpu>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source file='/var/lib/libvirt/images/sss.img'/>
      <target dev='vda' bus='virtio'/>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' cache='writethrough'/>
      <source dev='/dev/cdrom'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
    </disk>
    <interface type='network'>
      <source network='default'/>
      <mac address='52:54:00:c2:72:1e'/>
      <model type='virtio'/>
    </interface>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' keymap='en-us'/>
    <console type='pty'/>
    <video>
      <model type='cirrus'/>
    </video>
  </devices>
</domain>


Version-Release number of selected component (if applicable):
python-virtinst-0.500.3-5.el6.noarch

How reproducible:
always

Steps to Reproduce:
1.as description
2.
3.
  
Actual results:
--disk /dev/cdrom not be regonized as install source

Expected results:
--disk /dev/cdrom will be regonized as install source

Additional info: