after syncing the mysql-openrc package running rc-service mysql start the following error:

my_print_defaults: unknown variable 'config-file=/etc/mysql/my.cnf'

this is possibly because the init script has these lines:

get_config() {
        my_print_defaults --config-file="$1" mysqld |
        sed -n -e "s/^--$2=//p" 
}

although I haven't been able to make mysql (MariaDB) work with OpenRC, to fix this error, the line should be changed to:

get_config() {
        my_print_defaults --defaults-file="$1" mysqld |
        sed -n -e "s/^--$2=//p" 
}