====== Driver ======
    lsmod: list drivers

Remove driver

    sudo modprobe -r pl2303

Load driver

    sudo modprobe pl2303
    
Prevent loading of module. Add module name to blacklist
    /etc/modprobe.d/blacklist.conf
    
But note that adding it to the blacklist file might not be enough by itself as most distributions load the ehci_hcd module already during initrd, as such you might need to rebuild your initrd after adding it to the blacklist for it to have effect.

To rebuilt your initrd on a Red Hat/Fedora system, run the following command

    mkinitrd -f /boot/initrd-$(uname -r).img $(uname -r)
    
=====  disabling ehci_hcd =====

If your distribution (like Fedora 11) instead compiled the ehci_hcd support directly into the kernel, you cannot unload or blacklist it.

In such cases you can unbind it in sysfs, but first we need to find what the PCI device number of the EHCI controller is as follows;

    lspci|grep -i ehci

On a ThinkPad T41 this returns

    00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 01)

To unbind the ehci_hcd support from the PCI device, run the following command (adjust PCI location, based on lspci result)

     echo -n "0000:00:1d.7" > /sys/bus/pci/drivers/ehci_hcd/unbind

To automatically unload it on bootup, simply add the last command to /etc/rc.local.