Below is while /dev/hdb optical drive was loop mounted

$ strace /usr/bin/wodim -scanbus dev=/dev/hdb &>/tmp/wodim-scanbus.log-hdb

$ cat /tmp/wodim-scanbus.log-hdb

execve("/usr/bin/wodim", ["/usr/bin/wodim", "-scanbus", "dev=/dev/hdb"], [/* 31 vars */]) = 0
brk(0)                                  = 0x80a1000
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7fac000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=79228, ...}) = 0
mmap2(NULL, 79228, PROT_READ, MAP_PRIVATE, 3, 0) = 0xa7f98000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libcap.so.1", O_RDONLY)      = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\20\r\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=11024, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7f97000
mmap2(NULL, 14676, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xa7f93000
mmap2(0xa7f96000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2) = 0xa7f96000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\260e\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1356012, ...}) = 0
mmap2(NULL, 1361520, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xa7e46000
mmap2(0xa7f8d000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x147) = 0xa7f8d000
mmap2(0xa7f90000, 9840, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xa7f90000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7e45000
set_thread_area({entry_number:-1 -> 6, base_addr:0xa7e456b0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xa7f8d000, 4096, PROT_READ)   = 0
munmap(0xa7f98000, 79228)               = 0
geteuid32()                             = 1000
getrlimit(RLIMIT_NOFILE, {rlim_cur=1024, rlim_max=1024}) = 0
brk(0)                                  = 0x80a1000
brk(0x80c2000)                          = 0x80c2000
open("/etc/wodim.conf", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=1471, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7fab000
_llseek(3, 0, [0], SEEK_SET)            = 0
read(3, "# wodim.dfl Copyright 2006 E. Bl"..., 4096) = 1471
_llseek(3, 1471, [1471], SEEK_SET)      = 0
read(3, "", 4096)                       = 0
_llseek(3, 0, [0], SEEK_SET)            = 0
read(3, "# wodim.dfl Copyright 2006 E. Bl"..., 4096) = 1471
_llseek(3, 1471, [1471], SEEK_SET)      = 0
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xa7fab000, 4096)                = 0
fstat64(2, {st_mode=S_IFREG|0644, st_size=3030, ...}) = 0
uname({sys="Linux", node="sarge", ...}) = 0
stat64("/sys/kernel", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
mmap2(NULL, 970752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7d58000
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
write(2, "Error trying to open /dev/hdb ex"..., 93Error trying to open /dev/hdb exclusively (Device or resource busy)... retrying in 1 second.
) = 93
nanosleep({0, 999999000}, NULL)         = 0
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
write(2, "Error trying to open /dev/hdb ex"..., 93Error trying to open /dev/hdb exclusively (Device or resource busy)... retrying in 1 second.
) = 93
nanosleep({1, 0}, NULL)                 = 0
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
write(2, "Error trying to open /dev/hdb ex"..., 93Error trying to open /dev/hdb exclusively (Device or resource busy)... retrying in 1 second.
) = 93
nanosleep({0, 999999000}, NULL)         = 0
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
write(2, "Error trying to open /dev/hdb ex"..., 93Error trying to open /dev/hdb exclusively (Device or resource busy)... retrying in 1 second.
) = 93
nanosleep({1, 0}, NULL)                 = 0
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
write(2, "Error trying to open /dev/hdb ex"..., 82Error trying to open /dev/hdb exclusively (Device or resource busy)... giving up.
) = 82
nanosleep({0, 999999000}, NULL)         = 0
open("/dev/hdb", O_RDWR|O_NONBLOCK|O_EXCL|O_LARGEFILE) = -1 EBUSY (Device or resource busy)
open("/proc/mounts", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7fab000
read(3, "rootfs / rootfs rw 0 0\nnone /sys"..., 1024) = 548
write(2, "WARNING: /dev/hdb seems to be mo"..., 39WARNING: /dev/hdb seems to be mounted!
) = 39
read(3, "", 1024)                       = 0
close(3)                                = 0
munmap(0xa7fab000, 4096)                = 0
munmap(0xa7d58000, 970752)              = 0
write(2, "/usr/bin/wodim: Device or resour"..., 41/usr/bin/wodim: Device or resource busy. ) = 41
write(2, "\nCannot open SCSI driver!\nFor po"..., 245
Cannot open SCSI driver!
For possible targets try 'wodim --devices' or 'wodim -scanbus'.
For possible transport specifiers try 'wodim dev=help'.
For IDE/ATAPI devices configuration, see the file README.ATAPI.setup from
the wodim documentation.
) = 245
exit_group(-1)                          = ?
Process 24669 detached