scsi/sr: add no_read_disc_info scsi_device flag

Some USB devices emulate a usb-mass-storage attached (scsi) cdrom device,
usually this fake cdrom contains the windows software for the device.
While working on supporting Appotech ax3003 based photoframes, which do
this I discovered that they will go of into lala land when ever they see a
READ_DISC_INFO scsi command.

Thus this patch adds a scsi_device flag (which can then be set by the
usb-storage driver through an unsual-devs entry), to indicate this, and
makes the sr driver honor this flag.

I know this sucks, but as discussed on linux-scsi list there is no other
way to make this device work properly.

Looking at usb traces made under windows, windows never sends a
READ_DISC_INFO during normal interactions with a usb cdrom device.  So as
this cdrom emulation thingie becomes more common we might see more of this
problem.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 50cb34ffef11..e8c2433ad8a8 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -148,6 +148,7 @@ struct scsi_device {
         unsigned retry_hwerror:1;       /* Retry HARDWARE_ERROR */
         unsigned last_sector_bug:1;     /* do not use multisector accesses on
                                            SD_LAST_BUGGY_SECTORS */
+        unsigned no_read_disc_info:1;   /* Avoid READ_DISC_INFO cmds */
         unsigned is_visible:1;  /* is the device visible in sysfs */
 
         DECLARE_BITMAP(supported_events, SDEV_EVT_MAXBITS); /* supported events */