Fellow Engineers, Is there any way to adjust the speed of one USB 2.0 device without affecting other USB devices attached to the same Root Hub?
I have a USB mass storage device that is USB 2.0 compatible. It enumerates correctly, and generally works fine at High Speed (480 mbps). For a variety of EMI related reasons, I find that it is necessary for me to run this device at Full Speed (12 mbps). In my application, speed is not an issue, but EMI is. I know that the simple solution is to bind the UHCI driver to the Root Hub, instead of the EHCI driver, but this has the unfortunate side effect of forcing all USB devices to work in 1.1 mode. I would like to avoid this since there is another USB mass storage device for which there are no EMI issue that I would like to continue to run at High Speed. I don't mind kernel hacking to get this to work, but I was hoping someone out there already had a simple sysfs patch, or some such, that would allow simple user space adjustment of a device's speed. To throw one more complication into the mix, I would, in the end, like to find a way to force any device connected to a particular physical USB port to run at Full Speed instead of High Speed. Note that I am running Debian Etch (kernel 2.6.18). If a feature like this is already implemented in a later kernel, or one of the experimental branches, then please let me know, and point out the relevant source files. I could likely backport the changes as necessary for my kernel. Thanks for your help and comments, Joel ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
