Commentators have normally observed that Ἰησοῦ Χριστοῦ (Revelation 1:1) could be a subjective genitive ("from Christ") or an objective genitive ("about Christ"). Wallace believes the construction could be either an objective genitive or a plenary genitive (both subjective and objective at the same time); A.T. Robertson also seems to favor the objective genitive for this construction. But David Aune suggests that Ἰησοῦ Χριστοῦ is a subjective genitive since the next clause in the text is: ἣν ἔδωκεν αὐτῷ ὁ Θεός. As indicated by Aune's comment, the scripture's context must ultimately decide what type of genitive we have in Rev. 1:1.
Another factor that might have a bearing on this issue is that John refers to Jesus Christ with the datival form αὐτῷ in Rev. 1:1b. Aune thus reasons that there are a number of instances in Revelation where the indirect object is the subject of the verb in the following clause (Rev. 2:21), although he cautions us that these instances are all subordinate clauses.