How to control Port Indicator on USB Hub

some background-story:
Some days ago i had to copy a pdf file to multiple usb sticks for customers. in this process i wished i could write a script that blinks the port led of a port where the copying and unmounting was finished. (i only had a script that copied the content to a freshly inserted stick but didn't know when it is ready to exchange)

Today i found that the lcd4linux project has a plugin to just do this.
they explain that this functionality is part of the USB 2.0 Specification - Section '11.5.3 Port Indicator' I have looked into this document and theoretically it is possible to switch the port indicators to manual mode - then the host can control the indicator. The suggested meanings for both modes are:

• Color: Definition
• Off: Not operational
• Amber: Error condition
• Green: Fully operational
• Blinking Off/Green: Software attention
• Blinking Off/Amber: Hardware attention
• Blinking Green/Amber: Reserved

(source: Table 11-7. Port Indicator Color Definitions)

In Section '11.24.2.7.1.10 PORT_INDICATOR' there is some more information about the request to use these features. It can have 4 states:

• Value: Definition (request value)
• 0: automatic
• 1: amber
• 2: green
• 4: off
• 5..: reserved

(source: Table 11-25. Port Indicator Selector Codes)

i have looked around in /sys/bus/usb/devices/ but didn't found a value that looked promising.
Is it possible to control this from a user-space application in linux or somewhere in /sys/*?

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