The message is simply informational and most of the time harmless to the system. Messages like this usually occur after a kernel update and appear when a module that was used by the kernel previously is not being used or is not loaded anymore. However, sometimes this message appears because the system is probing for hardware and there is an error in loading a device for use.
You can ignore these messages in most cases and can turn them off, if you find that the device is working properly. However, before turning the messages off, you should make sure that they do not indicate a problem on your system. To do this, look up the block-major or char-major number in the MAKEDEV devices.txt file. (Note: You can quickly find this by running a locate devices.txt which should show it at /usr/share/doc/MAKEDEV-/devices.txt.) Once you find this file on your system, view the contents of the file and look up the block-major and char-major in question. This should help you determine which device the system cannot locate the module for. If you match a device, verify that the device is working properly. If the device is working properly or if you do not find a match, you can turn the messages off.
To turn the messages off, add a line similar to the following in your /etc/modules.conf file:
alias block-major-## off
alias char-major-## off
where ## is the number provided in the /var/log/messages warning. You must repeat the alias line for each block-major-## and char-major-## that appears in the log. The messages should stop occurring after the next boot.
Search for them like this:
grep "56 char" devices.txt
grep "56 block" devices.txt