How to determine the usb port speed in embedded devices running the linux kernel?
+2
A:
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 or 480. The first two indicate USB1 (low speed or full speed) and the third USB2.
caf
2009-12-25 23:31:21
A:
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.
Andrew Roca
2010-01-02 20:51:45