[Libcdio-devel] problems with libcdio on openbsd (and probably netbsd too)

[Edd Barrett]

Hi libcdio developers!

I'm an OpenBSD developer trying to get our ancient libcdio package up to
date. Having spent some time debugging, I've found two problems.

1) The device detection logic is broken.

On openbsd, the netbsd driver is used. To find available drives, libcdio
parses the output of a sysctl to get the available CD drives, but the
netbsd format of this string differs from openbsd. I've patched it
locally with code which simply finds devices by opening /dev/rcd[0-9]c.
That would probably work on netbsd too.

2) Error and warning handling in netbsd.c seems wrong.

If you have two CD drives, the first is empty, the second contains the
disk you want to access, cdio_get_devices_with_cap() will simply exit().

cdio_get_devices_with_cap() is a loop which queries devices in order. It
calls cdio_get_first_track_num(), then get_first_track_num_netbsd() and
finally _cdio_read_toc(), where you have:

---8<---
          res = ioctl(_obj->gen.fd, CDIOREADTOCHEADER, &_obj->tochdr);          
  
          if (res < 0) {                                                        
  
                  cdio_error("error in ioctl(CDIOREADTOCHEADER): %s\n",         
  
                             strerror(errno));                                  
  
                  return false;                                                 
  
          } 
--->8---

When the empty /dev/rcd0c is queried, the ioctl returns an error, and
cdio_error() exits. I think this is wrong. I'm testing using audacious,
and it just disappears if a drive is empty. Audacious never had a chance
to show the user an error message! I'd expect libraries to never exit()
unless it really can't continue.

If I comment the call to cdio_error(), I can play a CD from the second
drive using audacious. The `return false` even suggests that the author
of this code was expecting cdio_error() to return.

I suspect it's broken for NetBSD too (but I have not tried). They have a
patch in their tree which stops cdio_error() from exiting!
http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/misc/libcdio/patches/patch-aa?rev=1.5&content-type=text/x-cvsweb-markup

There are a ton more calls to cdio_error() in netbsd.c, many of them
look like they too should not stop the program, but maybe be downgraded
to cdio_warn(), or even be removed(?). By comparison, there isn't a
single call to cdio_error() in gnu_linux.c.

I wonder if one of the core libcdio developers could comment? Providing
that an appropriate error is returned, should all of the cdio_error()s
be at least cdio_warn()s?

Thanks!

-- 
Best Regards
Edd Barrett

http://www.theunixzoo.co.uk