Delegating Universal Serial Bus Functionality
A method of implementing USB Host functionality specifically designed to ensure a secure and resilient USB-On-The-Go implementation. A USB Hub Driver is configured so that it is able to nominate a portion of the USB topology to be transferred to the control of a peripheral driver or function driver. This nomination process generates a token that is associated with the nominated portion. The token is passed by the Hub Driver to the peripheral driver or function driver. The peripheral driver or function driver then uses the token to claim control over the nominated portion of the USB topology. The token can subsequently be transferred to other software entities as appropriate.
1 . A method of connecting one or more USB devices to a computing device comprising a USB topology having a USB Root Hub, wherein control over a portion of the USB topology is only granted to a software entity upon presentation of an electronic token associated with the said portion of the USB topology.
2 . A method according to claim 1 wherein the electronic token originates from the USB Root Hub of the USB topology.
3 . A method according to claim 1 wherein ownership of an electronic token is transferred from a first software entity to a second software entity by means of the first software entity providing the electronic token to the second software entity and by the second software entity presenting the token to the USB Root Hub.
4 . A method according to claim 3 wherein the one or more software entities comprise processes, threads or classes.
5 . A method according to claim 1 wherein a first token type is used for USB peripheral drivers and a second token type is used for USB function drivers.
6 . A method according to claim 1 wherein an entity may relinquish control of a portion of the USB topology by handing over the electronic token either to the entity by which it was originally nominated or to the USB Root Hub.
7 . A method according to claim 1 further comprising using a capability model for checking that an entity presenting an electronic token should be granted control over a portion of the USB topology.
8 . A method according to claim 7 wherein the electronic tokens are distributed through the use of an open distribution mechanism
9 . A method according to claim 8 wherein the open distribution mechanism comprises a publish and subscribe mechanism
10 . A method according to claim 1 wherein the USB topology is implemented in accordance with the USB-OTG specification.
11 . A computing device comprising a USB topology having a USB Root Hub, and arranged to enable control over a portion of the USB topology to be granted to a software entity upon presentation of an electronic token associated with the said portion of the USB topology.
12 . A device according to claim 11 wherein the electronic token originates from the USB Root Hub of the USB topology.
13 . A device according to claim 11 wherein ownership of an electronic token is transferred from a first software entity to a second software entity by means of the first software entity providing the electronic token to the second software entity and by the second software entity presenting the token to the USB Root Hub.
14 . A device according to claim 13 wherein the one or more software entities comprise processes, threads or classes.
15 . A device according to claim 11 wherein a first token type is used for USB peripheral drivers and a second token type is used for USB function drivers.
16 . A device according to claim 11 wherein an entity may relinquish control of a portion of the USB topology by handing over the electronic token either to the entity by which it was originally nominated or to the USB Root Hub.
17 . A device according to claim 11 wherein a capability model is used for checking that an entity presenting an electronic token should be granted control over a portion of the USB topology.
18 . A device according to claim 17 wherein the electronic tokens are distributed through the use of an open distribution mechanism
19 . A device according to claim 18 wherein the open distribution mechanism comprises a publish and subscribe mechanism
20 . A device according to claim 11 wherein the USB topology is implemented in accordance with the USB-OTG specification.
21 . A device according to claim 11 comprising a mobile phone.
22 . An operating system for causing a computing device to operate in accordance with a method as claimed in claim 1 .