cdrom_id: use the old MMC fallback

https://bugzilla.redhat.com/show_bug.cgi?id=1038015
The problem seems to be that the your virtual DVD is emulating a really
old DVD device, and doing it kind of strangely.

> dracut:# /lib/udev/cdrom_id --debug /dev/sr0
> probing: '/dev/sr0'
> INQUIRY: [IMM     ][Virtual CD/DVD   ][0316]
> GET CONFIGURATION failed with SK=5h/ASC=24h/ACQ=00h

So your virtual drive rejects the GET CONFIGURATION command as illegal.

Other pre-MMC2 drives that don't accept this command usually return the
error
SK=5h,ASC=20h (invalid/unsupported command code), in which case cdrom_id
tries an older method, and then ID_CDROM_MEDIA_TRACK_COUNT_DATA gets set
and all the /dev/disk/by-label (etc) links get set up.

The virtual drive returns the error SK=5h,ASC=24h (invalid field in
Command Descriptor Block), which cdrom_id doesn't handle, so it gives up
and the links never get made.

The ideal solution would be to make the IMM to emulate a device that's
less than 15 years old, but I'm not going to hold my breath waiting for
that.

So probably cdrom_id should also use the old MMC fallback when the error
is SK=5h,ASC=24h, and then all of this would work as expected.

Suggested-by:Luca Miccini <lmiccini@redhat.com>

diff --git a/src/udev/cdrom_id/cdrom_id.c b/src/udev/cdrom_id/cdrom_id.c
index 93467c2d35b0b95734570536dd8cb996f9ed8e85..33b2bc33317c00c2437c6bbb49f8e32a504df710 100644 (file)
--- a/src/udev/cdrom_id/cdrom_id.c
+++ b/src/udev/cdrom_id/cdrom_id.c
@@ -556,7 +556,7 @@ static int cd_profiles(struct udev *udev, int fd)
         if ((err != 0)) {
                 info_scsi_cmd_err(udev, "GET CONFIGURATION", err);
                 /* handle pre-MMC2 drives which do not support GET CONFIGURATION */
-                if (SK(err) == 0x5 && ASC(err) == 0x20) {
+                if (SK(err) == 0x5 && (ASC(err) == 0x20 || ASC(err) == 0x24)) {
                         log_debug("drive is pre-MMC2 and does not support 46h get configuration command");
                         log_debug("trying to work around the problem");
                         ret = cd_profiles_old_mmc(udev, fd);