ASM disks can be configured using raw devices, block devices or ASMLib.
On Linux is a best practice to configure it using ASMLib, as it simplifies ASM management as well as optimize IO. Usually you will configure ASMLib to start automatically at server reboot and to take care of ASM Disks ownership and permissions, this is done once on each server and that's it, every new ASM Disk will be managed the same way. ASMLib will also stamp the ASM disks with an ASMLabel thus avoiding the problems related to Linux dynamic device naming.
Otherwise with raw devices you need to configure scripts to setup ownership and permissions, and add every new disk to them as it is created.
Some old ASM based databases were implemented when ASMLib was not available for all Linux Kernels. If this is your case is advised to migrate to ASMLib.
The migration process is very simple, it consists on adding an ASMLib Label on the headers of each disk using the force-renamedisk command; still it has several steps that need to be followed carefully.
A step by step example can be seen on this document: Migration from Raw Devices to ASMLib