int open_for_data()

in cdrom.c [1051:1155]

• 79 lines of code
• 17 McCabe index (conditional complexity)

int open_for_data(struct cdrom_device_info *cdi)
{
	int ret;
	const struct cdrom_device_ops *cdo = cdi->ops;
	tracktype tracks;
	cd_dbg(CD_OPEN, "entering open_for_data\n");
	/* Check if the driver can report drive status.  If it can, we
	   can do clever things.  If it can't, well, we at least tried! */
	if (cdo->drive_status != NULL) {
		ret = cdo->drive_status(cdi, CDSL_CURRENT);
		cd_dbg(CD_OPEN, "drive_status=%d\n", ret);
		if (ret == CDS_TRAY_OPEN) {
			cd_dbg(CD_OPEN, "the tray is open...\n");
			/* can/may i close it? */
			if (CDROM_CAN(CDC_CLOSE_TRAY) &&
			    cdi->options & CDO_AUTO_CLOSE) {
				cd_dbg(CD_OPEN, "trying to close the tray\n");
				ret=cdo->tray_move(cdi,0);
				if (ret) {
					cd_dbg(CD_OPEN, "bummer. tried to close the tray but failed.\n");
					/* Ignore the error from the low
					level driver.  We don't care why it
					couldn't close the tray.  We only care 
					that there is no disc in the drive, 
					since that is the _REAL_ problem here.*/
					ret=-ENOMEDIUM;
					goto clean_up_and_return;
				}
			} else {
				cd_dbg(CD_OPEN, "bummer. this drive can't close the tray.\n");
				ret=-ENOMEDIUM;
				goto clean_up_and_return;
			}
			/* Ok, the door should be closed now.. Check again */
			ret = cdo->drive_status(cdi, CDSL_CURRENT);
			if ((ret == CDS_NO_DISC) || (ret==CDS_TRAY_OPEN)) {
				cd_dbg(CD_OPEN, "bummer. the tray is still not closed.\n");
				cd_dbg(CD_OPEN, "tray might not contain a medium\n");
				ret=-ENOMEDIUM;
				goto clean_up_and_return;
			}
			cd_dbg(CD_OPEN, "the tray is now closed\n");
		}
		/* the door should be closed now, check for the disc */
		ret = cdo->drive_status(cdi, CDSL_CURRENT);
		if (ret!=CDS_DISC_OK) {
			ret = -ENOMEDIUM;
			goto clean_up_and_return;
		}
	}
	cdrom_count_tracks(cdi, &tracks);
	if (tracks.error == CDS_NO_DISC) {
		cd_dbg(CD_OPEN, "bummer. no disc.\n");
		ret=-ENOMEDIUM;
		goto clean_up_and_return;
	}
	/* CD-Players which don't use O_NONBLOCK, workman
	 * for example, need bit CDO_CHECK_TYPE cleared! */
	if (tracks.data==0) {
		if (cdi->options & CDO_CHECK_TYPE) {
		    /* give people a warning shot, now that CDO_CHECK_TYPE
		       is the default case! */
		    cd_dbg(CD_OPEN, "bummer. wrong media type.\n");
		    cd_dbg(CD_WARNING, "pid %d must open device O_NONBLOCK!\n",
			   (unsigned int)task_pid_nr(current));
		    ret=-EMEDIUMTYPE;
		    goto clean_up_and_return;
		}
		else {
		    cd_dbg(CD_OPEN, "wrong media type, but CDO_CHECK_TYPE not set\n");
		}
	}

	cd_dbg(CD_OPEN, "all seems well, opening the devicen");

	/* all seems well, we can open the device */
	ret = cdo->open(cdi, 0); /* open for data */
	cd_dbg(CD_OPEN, "opening the device gave me %d\n", ret);
	/* After all this careful checking, we shouldn't have problems
	   opening the device, but we don't want the device locked if 
	   this somehow fails... */
	if (ret) {
		cd_dbg(CD_OPEN, "open device failed\n");
		goto clean_up_and_return;
	}
	if (CDROM_CAN(CDC_LOCK) && (cdi->options & CDO_LOCK)) {
			cdo->lock_door(cdi, 1);
			cd_dbg(CD_OPEN, "door locked\n");
	}
	cd_dbg(CD_OPEN, "device opened successfully\n");
	return ret;

	/* Something failed.  Try to unlock the drive, because some drivers
	(notably ide-cd) lock the drive after every command.  This produced
	a nasty bug where after mount failed, the drive would remain locked!  
	This ensures that the drive gets unlocked after a mount fails.  This 
	is a goto to avoid bloating the driver with redundant code. */ 
clean_up_and_return:
	cd_dbg(CD_OPEN, "open failed\n");
	if (CDROM_CAN(CDC_LOCK) && cdi->options & CDO_LOCK) {
			cdo->lock_door(cdi, 0);
			cd_dbg(CD_OPEN, "door unlocked\n");
	}
	return ret;
}