adnominal genitive and semantic inference.
The adnominal genitive merely predicates that there is a meaningful relation between the (pro)noun in the genitive and the head nominal. It is up to the addressee to infer the nature of that relation in the context of the utterance. When New Testament writers want to increase the level of explication, they may choose and indeed do choose more specific morphosyntactic devices. Compare the more explicit tēn ek theou dikaiōsunēn,“the righteousness from God” in Philippians 3:9a containing the source preposition ek with the more implicit adnominal genitive in Romans1:17, dikaiōsunē theou, “righteousness of God.”In the opening words of the Apocalypse of St. John, "the revelation of Jesus Christ" apokalupsis Ihsou Christou, John left the relationship between the head noun apokalupsis and genitives Ihsou Christou underdetermined (unspecified). As it stands the genitive tells us that there is some meaningful relationship between the head noun and the nouns in genitive case. That is the total extent of what is in the "code." In linguistic terminology that is the explicature (what is explicit in the text). The implicitures (what is implied, but derived by inference) are multiple. In other words, had John wanted to narrow down the explicit meaning he would have used a preposition with Jesus Christ, indicating that Jesus was the source, subject, agent, object, ... of the revelation. But John didn't do that so it is reasonable to conclude that he didn't intend to restrict the meaning to any one of these options.
I suspect there might be some greek readers who think that apokalupsis Ihsou Christou in Rev 1:1 is an obvious example of the subjective genitive. Certainly there are plenty of commentators who read it that way, D. Aune (Rev. WBC, v1 p.6) translates it "This is a revelation from Jesus Christ ..." which makes Jesus the source but in the notes he calls it a subjective genitive. A. J. Hort breaks from the heard, but few follow him. It isn't important IMO whether we follow Hort or the rest of them.
The problem is the compelling urge (an artifact of bad grammars and instruction) to nail down the semantic significance with either/or style analysis, where the essence of the adnominal genitive is semantic open-endedness (see N. Turner Syntax, pp. 210-211 and M. Zerwick pp. 13-14). Overly specific translation "a revelation from Jesus Christ" dramatically alters the meaning by placing undo stress on the "source" aspect of the genitive. G. Beale (Rev. NIGTC p. 184) gets it right, John intentionally left the meaning of apokalupsis Ihsou Christou open-ended.
 Biblical Scholars, Translators and Bible Translations, Lourens de Vries, S&I 2, no. 2 (2008): 141-159