Message-based identification of an electronic device

Abstract

A message-based identification process can facilitate reliable interoperation between accessories and host devices. During an identification process, the devices can negotiate an operating agreement that specifies particular communications (e.g., messages) that each device is permitted to send to or receive from the other, for example by having one device send a list of specific messages that it intends to send to and/or receive from the other. The other device can review the proposal and either accept or reject it. If a proposal is accepted, the devices can begin interoperating using messages that were included in the agreed-upon proposal while ignoring any received messages that were not included in the agreed-upon proposal.

What is claimed is: 
     
         1 . A method for establishing communication between a host device and an accessory according to a protocol that defines a universe of messages that are sendable by one of the host device and accessory to the other of the host device and the accessory, the method comprising:
 receiving, by the host device, an identification message from the accessory, wherein the identification message includes a proposal that partitions the universe of messages into a set of operative messages and a set of inoperative messages and wherein the proposal includes a listing identifying at least some of the messages in the universe of messages to be included in the set of operative messages, the listing including a first list identifying a first subset of the messages in the universe of messages defined by the protocol that the accessory proposes to send to the host device and a second list identifying a second subset of messages in the universe of messages defined by the protocol that the accessory proposes to receive from the host device; and   determining, by the host device, whether to accept or reject the proposal,   wherein determining whether to accept or reject the proposal is based in part by determining if a first message and a second message are identified by the listing, and if the first message is identified by the listing and the second message is not identified by the listing, then rejecting the proposal.   
     
     
         2 . The method of  claim 1  further comprising:
 sending, by the host device, a response message to the accessory, wherein the response message indicates whether the proposal is accepted or rejected. 
 
     
     
         3 . The method of  claim 2  wherein in the event that the host device accepts the proposal, using, by the host device, messages identified by the listing to interoperate with the accessory. 
     
     
         4 . The method of  claim 1  further comprising:
 receiving, by the host device, authentication information from the accessory, 
 wherein determining whether to accept or reject the proposal is based in part on the received authentication information. 
 
     
     
         5 . The method of  claim 1  wherein determining whether to accept or reject the proposal is based in part on determining whether the accessory is capable of responding to every one of the messages in the first subset and in part on determining whether the host device is capable of sending every one of the messages in the second subset. 
     
     
         6 . The method of  claim 1  wherein determining whether to accept or reject the proposal is based in part on determining whether the first subset and the second subset include a sufficient subset of messages to implement a functionality associated with at least one of the messages in at least one of the first subset or the second subset. 
     
     
         7 . The method of  claim 1  wherein the identification message further includes a device descriptor and wherein determining whether to accept or reject the proposal includes determining whether the messages in the first subset and the messages in the second subset are permissible based on the device descriptor. 
     
     
         8 . A method for establishing communication between a host device and an accessory according to a protocol that defines a universe of messages that are sendable by one of the host device and accessory to the other of the host device and the accessory, the method comprising:
 receiving, by the host device, an identification message from the accessory, wherein the identification message includes a proposal that partitions the universe of messages into a set of operative messages and a set of inoperative messages and wherein the proposal includes a listing identifying at least some of the messages in the universe of messages to be included in the set of operative messages, the listing including a first list identifying a first subset of the messages in the universe of messages defined by the protocol that the accessory proposes to send to the host device and a second list identifying a second subset of messages in the universe of messages defined by the protocol that the accessory proposes to receive from the host device; and   determining, by the host device, whether to accept or reject the proposal,   wherein determining whether to accept or reject the proposal is based in part on determining whether a first message in the first subset of messages or second subset of messages is not associated with a known capability of the accessory, and if the first message is not associated with a known capability of the accessory, then rejecting the proposal.   
     
     
         9 . The method of  claim 8  wherein the known capabilities of the accessory are identified by manufacturer and model information of the accessory. 
     
     
         10 . The method of  claim 9  wherein the identification message further includes a device descriptor, the device descriptor including the manufacturer and the model name of the accessory. 
     
     
         11 . The method of  claim 8  further comprising:
 receiving, by the host device, authentication information from the accessory, 
 wherein determining whether to accept or reject the proposal is based at least in part on the received authentication information. 
 
     
     
         12 . The method of  claim 8  further comprising:
 sending, by the host device, a response message to the accessory, wherein the response message indicates whether the proposal is accepted or rejected. 
 
     
     
         13 . The method of  claim 12  wherein in the event that the host device accepts the proposal, using, by the host device, messages from the listing to interoperate with the accessory. 
     
     
         14 . A method for establishing communication between a host device and an accessory according to a protocol that defines a universe of messages that are sendable by one of the host device and accessory to the other of the host device and the accessory, the method comprising:
 receiving, by the host device, an identification message from the accessory, wherein the identification message includes a proposal that partitions the universe of messages into a set of operative messages and a set of inoperative messages and wherein the proposal includes a listing identifying at least some of the messages in the universe of messages to be included in the set of operative messages, the listing including a first list identifying a first subset of the messages in the universe of messages defined by the protocol that the accessory proposes to send to the host device and a second list identifying a second subset of messages in the universe of messages defined by the protocol that the accessory proposes to receive from the host device;   receiving, by the host device, authentication information including a digital certificate;   determining, by the host device, whether to accept or reject the proposal,   wherein determining whether to accept or reject the proposal is based in part on whether messages in the first subset of messages and the second subset of messages are permissible based on the digital certificate.   
     
     
         15 . The method of  claim 14  further comprising:
 sending, by the host device, a response message to the accessory, wherein the response message indicates whether the proposal is accepted or rejected. 
 
     
     
         16 . The method of  claim 15  wherein in the event that the host device accepts the proposal, using, by the host device, messages from the listing to interoperate with the accessory. 
     
     
         17 . A method for establishing communication between a host device and an accessory according to a protocol that defines a universe of messages that are sendable by one of the host device and accessory to the other of the host device and the accessory, the method comprising:
 sending, by the accessory, an identification message to the host device, wherein the identification message includes a proposal that partitions the universe of messages into a set of operative messages and a set of inoperative messages and wherein the proposal includes a listing identifying at least some of the messages in the universe of messages to be included in the set of operative messages, the listing including a first list identifying a first subset of the messages in the universe of messages defined by the protocol that the accessory proposes to send to the host device and a second list identifying a second subset of messages in the universe of messages defined by the protocol that the accessory proposes to receive from the host device;   sending, by the accessory, authentication information to the host device; the authentication information including a digital certificate;   in response to sending the identification message and the authentication information, receiving, by the accessory, a response message from the host device, the response message indicating whether the proposal was accepted or rejected by the host device; and   in the event that the proposal was accepted, using, by the accessory, at least some of the messages from the first subset of messages and the second subset of messages to interoperate with the host device.   
     
     
         18 . The method of  claim 17  further comprising:
 in the event that the response message indicates that the proposal was rejected, sending, by the accessory, a modified proposal to the host device, the modified proposal including a modification to the listing identifying messages to be included in the set of operative messages. 
 
     
     
         19 . The method of  claim 17  further comprising:
 receiving, by the accessory, an identification request from the host device, 
 wherein the identification message is sent in response to receiving the identification request. 
 
     
     
         20 . The method of  claim 17  wherein the identification message further includes a device descriptor, the device descriptor including at least one of a name of a manufacturer of the accessory, a model name of the accessory, a serial number of the accessory, a hardware version identifier of the accessory, or a firmware version identifier of the accessory.