pktcdvd: add compat_ioctl handler

pkt_ioctl() implements the generic SCSI_IOCTL_SEND_COMMAND
and some cdrom ioctls by forwarding to the underlying block
device. For compat_ioctl handling, this always takes a
roundtrip through fs/compat_ioctl.c that we should try
to avoid, at least for the compatible commands.

CDROM_SEND_PACKET is an exception here, it requires special
translation in compat_blkdev_driver_ioctl().

CDROM_LAST_WRITTEN has no compat handling at the moment.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/block/pktcdvd.c

@@ -2663,6 +2663,28 @@ static int pkt_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd,
 	return ret;
 }
 
+#ifdef CONFIG_COMPAT
+static int pkt_compat_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	/* compatible */
+	case CDROMEJECT:
+	case CDROMMULTISESSION:
+	case CDROMREADTOCENTRY:
+	case SCSI_IOCTL_SEND_COMMAND:
+		return pkt_ioctl(bdev, mode, cmd, (unsigned long)compat_ptr(arg));
+
+
+	/* FIXME: no handler so far */
+	case CDROM_LAST_WRITTEN:
+	/* handled in compat_blkdev_driver_ioctl */
+	case CDROM_SEND_PACKET:
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+#endif
+
 static unsigned int pkt_check_events(struct gendisk *disk,
 				     unsigned int clearing)
 {
@@ -2684,6 +2706,9 @@ static const struct block_device_operations pktcdvd_ops = {
 	.open =			pkt_open,
 	.release =		pkt_close,
 	.ioctl =		pkt_ioctl,
+#ifdef CONFIG_COMPAT
+	.ioctl =		pkt_compat_ioctl,
+#endif
 	.check_events =		pkt_check_events,
 };