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How to programatically determine the usb port speed in embedded devices running the Linux kernel?

Answer 1

You can read /sys/bus/usb/devices/usb?/speed - it ll give you the bus speed of the root hub(s) in Mbps: either 1.5, 12, 480, 5000 or 10000. The first two indicate USB1 (low speed or full speed), the third USB2 and the fourth and fifth USB3.

Answer 2

This rather depends on were the code that needs the information is running. If you want to modify a kernel USB device drivers behavior based on connection speed then the usb_device struct that passed to the driver by the USB subsystem contains a speed enumeration. If you want an application in user space to detect the devices connection speed then try walking the /sys/bus/usb tree you should be able to identify your USB device by checking the idProduct and idVendor entries. Once you have a match then the speed entry will give you what you need. If you have multiple devices connected then you might need to figure a way to match USB id to specific device. Generally USB to device mappings vary on any hot plug support present whether the device supplies a serial number and the sub system that abstracts the functionality provided by the USB device.

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