misc/155925: CD tray is not locked even if using /dev/adc0.

[Alexander Best]

The following reply was made to PR misc/155925; it has been noted by GNATS.

From: Alexander Best <arundel at freebsd.org>
To: Jaakko Heinonen <jh at FreeBSD.org>
Cc: koie at suri.co.jp, bug-followup at FreeBSD.org
Subject: Re: misc/155925: CD tray is not locked even if using /dev/adc0.
Date: Sat, 26 Mar 2011 18:27:02 +0000

 On Sat Mar 26 11, Jaakko Heinonen wrote:
 > On 2011-03-25, Alexander Best wrote:
 > >  this issue is not limited to acd. using cdcontrol -f /dev/cd gives the same
 > >  behavior.
 > 
 > I think this is because cdcontrol(1) first issues the CDIOCALLOW ioctl
 > to unlock the tray. Does this patch fix your problem?
 > 
 > 	http://www.saunalahti.fi/~jh3/patches/cdcontrol-no-CDIOCALLOW.diff
 > 
 > I am inclined to think that the behavior is intentional.
 
 i think the actual issue is not cdcontrol(1) so much, as CDIOCALLOW itself.
 looking at this PR:
 
 http://www.freebsd.org/cgi/query-pr.cgi?pr=125139
 
 shouldn't CDIOCALLOW and CDIOCPREVENT have the same busy checks like CDIOCEJECT
 (as pointed out in the PR)?
 
 i haven't tested your patch, but i think it works. CDIOCEJECT checks the ref
 count. without the CDIOCALLOW and a ref count >= 1 the cd won't be ejected.
 
 i'm not sure whether CDIOCALLOW and CDIOCPREVENT should stay the way they are
 or not. making them dependent on the ref count won't allow ejecting a CD at
 all. this might cause problems if or some reason the ref count cannot be set
 to 0. e. g. unmounting a broken CD/DVD might fail. i'm not sure if umount -f
 will always suceeded, so we might not be able to reduce the ref count to 0 in
 certain situations.
 
 if in fact CDIOCALLOW/CDIOCPREVENT should work regardless of the ref count i
 think your patch is good to go. here are the other places CDIOCALLOW is being
 used:
 
 otaku% grep -r CDIOCALLOW *
 share/man/man4/cd.4:.It Dv CDIOCALLOW
 sys/cam/scsi/scsi_cd.c:	case CDIOCALLOW:
 sys/dev/ata/atapi-cd.c:    case CDIOCALLOW:
 sys/dev/mcd/mcd.c:	case CDIOCALLOW:
 sys/dev/scd/scd.c:	case CDIOCALLOW:
 sys/sys/cdio.h:#define	CDIOCALLOW	_IO('c',26)
 usr.sbin/cdcontrol/cdcontrol.c:		(void) ioctl (fd, CDIOCALLOW);
 usr.sbin/cdcontrol/cdcontrol.c:		(void) ioctl (fd, CDIOCALLOW);
 usr.sbin/cdcontrol/cdcontrol.c:		(void) ioctl (fd, CDIOCALLOW);
 usr.sbin/sysinstall/cdrom.c:		ioctl(fd, CDIOCALLOW);
 
 cheers.
 alex
 
 > 
 > -- 
 > Jaakko
 
 -- 
 a13x