Last September the USB Implementers Forum quietly published an update to the USB 2.0 specification… The Embedded USB2 Version 2.0 “eUSB2V2” supplement to provide for better performance with significantly higher data rates to USB 2.0 while maintaining the low-voltage electrical interface.
This eUSB2V2 update is intended to provide for more bandwidth for devices like integrated/embedded web cameras for allowing higher resolutions while maintaining low power requirements of 1.2V with Embedded USB. Any USB 2.0 updates nearly two and a half decades since USB 2.0 first premiered wasn’t on my bingo card. Only with the flow of “-next” patches getting ready for Linux 6.15 did I even realize of this recent spec update from a few months ago. The Linux kernel is now getting ready for eUSB2V2 hardware.
The eUSB2V2 bit rates can achieve as much as 4.8Gb/s.
Kannappan R with Intel along with other Intel engineers have been making updates to the Linux USB driver for handling the latest eUSB2v2 specs. A patch queued into USB-next for the Linux 6.15 kernel explains:
“Add support for the ‘eUSB2 Isochronous Endpoint Companion Descriptor’ introduced in the recent USB 2.0 specification ‘USB 2.0 Double Isochronous IN Bandwidth’ ECN.
It allows embedded USB2 (eUSB2) devices to report and use higher bandwidths for isochronous IN transfers in order to support higher camera resolutions on the lid of laptops and tablets with minimal change to the USB2 protocol.
The motivation for expanding USB 2.0 is further clarified in an additional Embedded USB2 version 2.0 (eUSB2v2) supplement to the USB 2.0 specification. It points out this is optimized for performance, power and cost by using the USB 2.0 low-voltage, power efficient PHY and half-duplex link for the asymmetric camera bandwidth needs, avoiding the costly and complex full-duplex USB 3.x symmetric link and gigabit receivers.
eUSB2 devices that support the higher isochronous IN bandwidth and the new descriptor can be identified by their device descriptor bcdUSB value of 0x0220″
Looks like we’ll still be seeing USB 2.0 (eUSB2) based laptop web cameras for years to come while now with higher resolutions coming while keeping costs low and without changes to power requirements. This latest USB 2.0 work from Intel will be part of the upcoming Linux 6.15 kernel cycle.
