On 05/14/2012 06:22 PM, Pete Batard wrote:
> On 2012.05.14 16:48, Uri Lublin wrote:
>> The scenario I was looking at is:
>> libusb_get_device_list
>> device = go over the list of devices and find the one with
>> appropriate vid,pid
>> libusb_open(device)
>> if failed:
>> install libusb device driver
>> rescan devices (call libusb_get_device_list and
>> libusb_free_device_list)
>> libusb_open(device)
> This shouldn't be too different from what I tested, so I'd expect it to
> work. open_with_vid_pid(), which is what I used in my test, is mostly a
> wrapper for get_device_list() + open() + free_device_list().
>
>> Maybe the problem can be solved in the application.
>> Likely I can unref it before driver installation, and find it again
>> after the installation.
>> That would be similar of using libusb_open_with_vid_pid.
> Yeah. What I'm not clear about is that if libusb_open failed, your
> refcount for the device should be zero when you destroy the device list,
> so the next time you call get_device_list, you should be able to find
> the device with the WinUSB driver instead.
>
> A device that cannot be opened should not be kept instantiated by
> libusbx outside of get_device_list-free_device_list, so maybe the only
> thing you miss is ensuring the device list is destroyed before you call
> on get_device_list again.
We keep a list of all the devices that are plugged into the system
(including cold-plug devices), not only opened devices.
That way users can pick a device they want to share with guests.
My plan is to check how hard it would be to unreference the
libusb_device before installing the driver, and reference back
after the installation.
Thanks,
Uri.
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