ACR122U is a cheap and buggy USB NFC reader. PCSC-Lite/M.U.S.C.L.E. is an open source framework providing support for smartcard readers, including NFC, on UNIX-like systems.
The included diff introduces a workaround for the bug in the ACR122U reader that makes it use "one less" sequence number in the response frame if the request frame was longer than 64 bytes.
It works for me (and does not break on another "correct" CCID reader that I have at hand). I just wanted to share it in case it could be useful for somebody.
It is possible that the bug is specific to a subset of the ACR122U readers, and there exist readers with the USB ID 072f:2200 that do not have this bug. My patch should not break on them, but of course I had no way to test it.pcsclite-ccid-ACR122U.diff is created on September 8, 2013 against the SVN "trunk" version of pcsclite.
12 September 2013, a representative of ACS informed me that they fixed this bug in the device that is now shipping.
= Eugene Crosser