Hi all, I am currently implementing one SC driver and I have run into a problem with T=0 Case 2 command response length.
Standard says that this response can be : 1) 6C Luicc (i.e. 2 bytes); or 2) INS [Data(Luicc)] 90 00 (i.e. Luicc + 3 bytes) There are other variations with "61" and "6C" PBs, but in any case it turns out that for the same command [CLA INS P1 P2 P3=00], response can vary in length and is not known in advance. I can not read byte by byte and analyse it because : 1) It should be done in a transport layer, so I have to exit my driver RX function 2) When I do this, there is a danger of RX FIFO overflow while I am in transport layer processing, because now driver is not popping bytes from RX FIFO (which is only 8 bytes). And if a card is sending long answer and I exited my driver code to analyse first byte, havoc might happen. As a result, before calling my drivers RX function I have to know in advance how much bytes I have to receive, and stay in my driver's RX function until I received this number of bytes, while popping RX FIFO to some location in memory. I have an impression that here : http://www.opensc-project.org/openct/browser/trunk/src/ifd/proto-t0.c in the code implemented by Olaf, byte by byte is analyzed. My question is also how this is possible, because card is sending you like a crazy, without stop. Do you have some interrupt in your driver for each byte arrived to remove it from your RX FIFO ? That would be too much interruptions for me, I want as much bytes as possible in the FIFO before interrupts arrive and tell me to pop it. What is the best way to implement Case 2 response END detection : 1) To demand always 256 (maximum) length from UICC and have timeout which will say : no more characters arriving, so it must be the end of message. 2) To insert some kind of T=0 dependence in the driver itself (datalink layer) which will take a look at every byte arriving (which I did not want to do. I wanted to keep byte sending/receiving transparent for the driver, and do analysis in the transport layer. I do not want to pollute my driver with T=0 dependencies). 3) Something other that I am missing right now ? BTW. Luicc is defined like : Luicc: exact length of data available in the UICC to be returned in response to the case 2 or 4 Command received by the UICC Is it always not known by the terminal before issuing first Case 2 command, or there is a way to know this value in advance (I guess no, and I guess it changes dynamically depending on the command and the card state.) BR, Drasko _______________________________________________ opensc-devel mailing list opensc-devel@lists.opensc-project.org http://www.opensc-project.org/mailman/listinfo/opensc-devel
