Simulated input/output devices

• US 9,418,181 B2
• Filed: 01/09/2013
• Issued: 08/16/2016
• Est. Priority Date: 01/09/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Kelley, John E., Myrick, Andrew D.
• Primary Examiner(s): Rivas, Omar Fernandez
• Assistant Examiner(s): Mapar, Bijan
• Application Number:
  US13/737,927
• Publication Number:
  US 20140195217A1
• Time in Patent Office: 1,315 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: G06F 9/455 Emulation; Interpretation; Software simulation, e.g. virtualisation or emulation of application or operating system execution engines

Abstract

In one or more embodiments, methods and apparatus are provided for simulating device communications such as those of the Universal Serial Bus (“USB”) or the like. The methods and apparatus involve receiving host requests that represent commands in a communication protocol and are associated with communication endpoints, distributing the host requests across the communication endpoints in the order that they are received, to their associated endpoints to generate a distribution of requests, generating a reordered plurality of host requests by selecting the host requests from the communication endpoints in an order based upon the order in which the requests are received and one or more simulation factors, receiving device requests from a simulated device in accordance with the communication protocol, merging the reordered host requests and the plurality of device requests to form a merged sequence of requests, and performing commands from the merged sequence of requests in the order.

Claims

1. A method of simulating communication between devices, the method comprising:

at a hardware simulator;

receiving, at a simulated device interface, a host request that represents a command from a host device for accessing a state register of a simulated device that is connected to the simulated device interface;

distributing the host request to a device endpoint of the simulated device interface;

generating, by simulating an operation of the simulated device, a device request for accessing the state register of the simulated device;

removing the host request from the device endpoint, wherein the receiving, generating, and removing are performed iteratively by concurrent threads;

determining a first time at which the device request is generated, and a second time at which the host request is removed from the device endpoint;

interleaving the host request and the device request into a merged sequence of requests such that, when the first time is earlier than the second time, the device request has priority over the host request; and

executing requests of the merged sequence of requests in an order in which the requests occur in the merged sequence of requests, wherein the requests include instructions for accessing state data stored by the state register.

2. The method of claim 1, wherein the simulated device is configured to provide information related to a simulated operating system on the simulated device.

3. The method of claim 1, further comprising:

splitting the host requests into packets.

4. The method of claim 1, wherein an arrangement of the merged sequence of requests is based on how many device endpoints are enabled.

5. The method of claim 3, wherein the host requests represent read or write transactions.

6. The method of claim 3, wherein the state data includes representations of registers and memory locations.

7. The method of claim 6, wherein the host requests are distributed simultaneous to the execution of requests of the merged sequence of requests.

8. The method of claim 1, wherein removing the host request from the device endpoint comprises determining whether the device endpoint is capable of receiving data.

9. The method of claim 1, wherein the host request, and device endpoint are associated with a Universal Serial Bus (USB).

10. A computing device comprising:

a processor;

a memory configured to store instructions that when executed by the processor cause the processor to perform steps that include;

receiving, at a simulated device interface, a host request that represents a command from a host device for accessing a state register of a simulated device that is connected to the simulated device interface;

distributing the host request to a device endpoint of the simulated device interface;

generating, by simulating an operation of the simulated device, a device request for accessing the state register of the simulated device;

removing the host request from the device endpoint, wherein the receiving, generating, and removing are performed iteratively by concurrent threads;

determining a first time at which the device request is generated, and a second time at which the host request is removed from the device endpoint;

interleaving the host request and the device request into a merged sequence of requests such that, when the first time is earlier than the second time, the device request has priority over the host request; and

executing requests of the merged sequence of requests in an order in which the requests occur in the merged sequence of requests, wherein the requests include instructions for accessing state data stored by the state register.

11. The system of claim 10, wherein the simulated device corresponds to a universal serial bus device that includes a simulated operating system.

12. The system of claim 10, wherein the steps further include:

determining whether any endpoints are available, and

retrieving only host requests that correspond to an available device endpoint.

14. The computing device of claim 10, wherein an arrangement of the merged sequence of requests is based on how many device endpoints are enabled.

15. The computing device of claim 10, wherein the steps further include:

splitting the host requests into packets.

16. The computing device of claim 10, wherein the host requests are distributed simultaneous to the execution of requests of the merged sequence of requests.

13. A non-transitory computer readable medium configured to store instructions that, when executed by a processor of a computing device, cause the computing device to perform steps that include:

receiving, at a simulated device interface, a host request that represents a command from a host device for accessing a state register of a simulated device that is connected to the simulated device interface;

distributing the host request to a device endpoint of the simulated device interface;

generating, by simulating an operation of the simulated device, a device request for accessing the state register of the simulated device;

removing the host request from the device endpoint, wherein the receiving, generating, and removing are performed iteratively by concurrent threads;

determining a first time at which the device request is generated, and a second time at which the host request is removed from the device endpoint;

interleaving the host request and the device request into a merged sequence of requests such that, when the first time is earlier than the second time, the device request has priority over the host request; and

executing requests of the merged sequence of requests in an order in which the requests occur in the merged sequence of requests, wherein the requests include instructions for accessing state data stored by the state register.

17. The non-transitory computer readable medium of claim 13, wherein the requests correspond to instructions to read from or write to the state register.

18. The non-transitory computer readable medium of claim 13, wherein an arrangement of the merged sequence of requests is based on how many device endpoints are enabled.

19. The non-transitory computer readable medium of claim 13, wherein removing the host request from the device endpoint comprises determining whether the device endpoint is capable of receiving data.

20. The non-transitory computer readable medium of claim 13, wherein the host requests are distributed simultaneous to the execution of requests of the merged sequence of requests.