POSIX FatFs "r" A_READ "r+" A_READ | A_WRITE "w" A_CREATE_ALWAYS | A_WRITE "w+" A_CREATE_ALWAYS | A_WRITE | A_READ "a" A_OPEN_APPEND | A_WRITE "a+" A_OPEN_APPEND | A_WRITE | A_READ "wx" A_CREATE_NEW | A_WRITE "w+x" A_CREATE_NEW | A_WRITE | FA_READ *