[Help-bash] /proc/.../cdrom/info not completely read

[humpty]

hi,

I encounter a problem when I try to read /proc/sys/dev/cdrom/info

whatever method I try, bash doesn't read the whole file

$ file=/proc/sys/dev/cdrom/info
$ while read line...done <"$file"
only outputs the first line

$ exec {foo}<"$file"
$ while read -u line
outputs about six lines, as does
$ mapfile -t myArray <"$file"
and
$ echo "$(<"$file")"

if I copy "$file" anywhere (say /tmp/) there is no problem any more.
This happens with BASH 4.2 on Debian, and openSuse (and BASH 3.3.4 on 
archlinux (I've been told))

what could be the reason for such a behaviour?
is there a full bash way around?

thank you.