device filtering support

[Xiaofan Chen]

On Wed, Feb 1, 2012 at 3:28 PM, Hans de Goede <hdegoede at redhat.com> wrote:
> Ok, so lets drop the class filtering bit, even then it still makes
> sense to:
> 1) Have a per filter rule allow/deny result, since we support wildcards
> it makes a lot of sense to also do this, so that you can deny a couple
> of devices from one manufacturer and then get all the others with 1
> allow rule

I am fine with this proposal.

> 2) Support filtering on bcdVersion this is part of the device descriptors
> just like vid/pid, so available at the same time and for some devices
> having a different bcdVersion means that it really is a completely
> different chipset but the vendor thought it would be a good idea to
> just resue the vid+pid and only change the version. Note that windows
> encourages this by allowing drivers to bind to specific versions.

I think this is fine as well even though I am not so sure about
the significance of this feature.

Take note we are talking about filtering during enumeration
(getting the device list), not after the enumeration. You can
filter many things after getting the device list.

Currently libusb-1.0 implementations enumerate all USB
device on all platforms which is quite an expensive operation,
especially under Windows. So this makes filtering during
enumeration process a desirable feature.

libusb-win32/libusbK use different mechanisms which makes
the enumeration faster since we mainly deal with specific
devices and enumerate the device with supported drivers.

-- 
Xiaofan