[libhid-discuss] LIBHID: Latest SVN Trunk: hid_opening.c: hid_compare_usb_device(): product_id matched incorrectly

[Andrew Silverman]

My recollection is that this is already a known bug that was never officially patched, as evidently libhid has long since been considered obsolete in favor of newer HID libraries (http://www.signal11.us/oss/hidapi/).  I have the same change in my own code that still works with the existing library.

-----Original Message-----
From: libhid-discuss [mailto:libhid-discuss-bounces+andrewsi=microsoft.com at lists.alioth.debian.org] On Behalf Of christopher.alan.becker at gmail.com
Sent: Sunday, April 19, 2015 7:15 PM
To: libhid-discuss at lists.alioth.debian.org
Subject: [libhid-discuss] LIBHID: Latest SVN Trunk: hid_opening.c: hid_compare_usb_device(): product_id matched incorrectly

Hi:

I ran into a situation with libhid where a USB product  ID of 0x0501 was matching on a USB device with a product ID of 0x0503.  I narrowed it down in hid_compare_usb_device() to the line below:
-----
((dev->descriptor.idProduct & match->product_id) == match->product_id)
-----

Tracing the values of the above, both match and dev descriptor, the values were showing correct (0x0501, 0x0503), but still evaluating as matched.

If I change the above code to just:
-----
(dev->descriptor.idProduct == match->product_id)
-----

Then the product ID's match correctly, and only 0x0501 matches 0x0501.  
Any ideas on why 0x0503 would match 0x0501 on the original code?

Actual hex codes were set/used in the passed HIDInterfaceMatcher struct.

As a side note, the vendor ID did not experience this problem. Latest SVN trunk (2015-04-19).

Thanks.


~ Chris

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