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+* For the user
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+NOTE: This document describes the usage of the high level CI API as
+in accordance to the Linux DVB API. This is a not a documentation for the,
+existing low level CI API.
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To utilize the High Level CI capabilities,
+
+(1*) This point is valid only for the Twinhan/clones
+  For the Twinhan/Twinhan clones, the dst_ca module handles the CI
+  hardware handling.This module is loaded automatically if a CI
+  (Common Interface, that holds the CAM (Conditional Access Module)
+  is detected.
+
+(2) one requires a userspace application, ca_zap. This small userland
+  application is in charge of sending the descrambling related information
+  to the CAM.
+
+This application requires the following to function properly as of now.
+
+        (a) Tune to a valid channel, with szap.
+          eg: $ szap -c channels.conf -r "TMC" -x
+
+        (b) a channels.conf containing a valid PMT PID
+
+          eg: TMC:11996:h:0:27500:278:512:650:321
+
+          here 278 is a valid PMT PID. the rest of the values are the
+          same ones that szap uses.
+
+        (c) after running a szap, you have to run ca_zap, for the
+          descrambler to function,
+
+          eg: $ ca_zap patched_channels.conf "TMC"
+
+          The patched means a patch to apply to scan, such that scan can
+          generate a channels.conf_with pmt, which has this PMT PID info
+          (NOTE: szap cannot use this channels.conf with the PMT_PID)
+
+
+        (d) Hopeflly Enjoy your favourite subscribed channel as you do with
+          a FTA card.
+
+(3) Currently ca_zap, and dst_test, both are meant for demonstration
+  purposes only, they can become full fledged applications if necessary.
+
+
+* Cards that fall in this category
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+At present the cards that fall in this category are the Twinhan and it's
+clones, these cards are available as VVMER, Tomato, Hercules, Orange and
+so on.
+
+* CI modules that are supported
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The CI module support is largely dependant upon the firmware on the cards
+Some cards do support almost all of the available CI modules. There is
+nothing much that can be done in order to make additional CI modules
+working with these cards.
+
+Modules that have been tested by this driver at present are
+
+(1) Irdeto 1 and 2 from SCM
+(2) Viaccess from SCM
+(3) Dragoncam
+
+* The High level CI API
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+* For the programmer
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+With the High Level CI approach any new card with almost any random
+architecture can be implemented with this style, the definitions
+insidethe switch statement can be easily adapted for any card, thereby
+eliminating the need for any additional ioctls.
+
+The disadvantage is that the driver/hardware has to manage the rest. For
+the application programmer it would be as simple as sending/receiving an
+array to/from the CI ioctls as defined in the Linux DVB API. No changes
+have been made in the API to accomodate this feature.
+
+
+* Why the need for another CI interface ?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This is one of the most commonly asked question. Well a nice question.
+Strictly speaking this is not a new interface.
+
+The CI interface is defined in the DVB API in ca.h as
+
+typedef struct ca_slot_info {
+        int num;               /* slot number */
+
+        int type;              /* CA interface this slot supports */
+#define CA_CI            1     /* CI high level interface */
+#define CA_CI_LINK       2     /* CI link layer level interface */
+#define CA_CI_PHYS       4     /* CI physical layer level interface */
+#define CA_DESCR         8     /* built-in descrambler */
+#define CA_SC          128     /* simple smart card interface */
+
+        unsigned int flags;
+#define CA_CI_MODULE_PRESENT 1 /* module (or card) inserted */
+#define CA_CI_MODULE_READY   2
+} ca_slot_info_t;
+
+
+
+This CI interface follows the CI high level interface, which is not
+implemented by most applications. Hence this area is revisited.
+
+This CI interface is quite different in the case that it tries to
+accomodate all other CI based devices, that fall into the other categories
+
+This means that this CI interface handles the EN50221 style tags in the
+Application layer only and no session management is taken care of by the
+application. The driver/hardware will take care of all that.
+
+This interface is purely an EN50221 interface exchanging APDU's. This
+means that no session management, link layer or a transport layer do
+exist in this case in the application to driver communication. It is
+as simple as that. The driver/hardware has to take care of that.
+
+
+With this High Level CI interface, the interface can be defined with the
+regular ioctls.
+
+All these ioctls are also valid for the High level CI interface
+
+#define CA_RESET          _IO('o', 128)
+#define CA_GET_CAP        _IOR('o', 129, ca_caps_t)
+#define CA_GET_SLOT_INFO  _IOR('o', 130, ca_slot_info_t)
+#define CA_GET_DESCR_INFO _IOR('o', 131, ca_descr_info_t)
+#define CA_GET_MSG        _IOR('o', 132, ca_msg_t)
+#define CA_SEND_MSG       _IOW('o', 133, ca_msg_t)
+#define CA_SET_DESCR      _IOW('o', 134, ca_descr_t)
+#define CA_SET_PID        _IOW('o', 135, ca_pid_t)
+
+
+On querying the device, the device yields information thus
+
+CA_GET_SLOT_INFO
+----------------------------
+Command = [info]
+APP: Number=[1]
+APP: Type=[1]
+APP: flags=[1]
+APP: CI High level interface
+APP: CA/CI Module Present
+
+CA_GET_CAP
+----------------------------
+Command = [caps]
+APP: Slots=[1]
+APP: Type=[1]
+APP: Descrambler keys=[16]
+APP: Type=[1]
+
+CA_SEND_MSG
+----------------------------
+Descriptors(Program Level)=[ 09 06 06 04 05 50 ff f1]
+Found CA descriptor @ program level
+
+(20) ES type=[2] ES pid=[201]  ES length =[0 (0x0)]
+(25) ES type=[4] ES pid=[301]  ES length =[0 (0x0)]
+ca_message length is 25 (0x19) bytes
+EN50221 CA MSG=[ 9f 80 32 19 03 01 2d d1 f0 08 01 09 06 06 04 05 50 ff f1 02 e0 c9 00 00 04 e1 2d 00 00]
+
+
+Not all ioctl's are implemented in the driver from the API, the other
+features of the hardware that cannot be implemented by the API are achieved
+using the CA_GET_MSG and CA_SEND_MSG ioctls. An EN50221 style wrapper is
+used to exchange the data to maintain compatibility with other hardware.
+
+
+/* a message to/from a CI-CAM */
+typedef struct ca_msg {
+        unsigned int index;
+        unsigned int type;
+        unsigned int length;
+        unsigned char msg[256];
+} ca_msg_t;
+
+
+The flow of data can be described thus,
+
+
+
+
+
+        App (User)
+        -----
+        parse
+          |
+          |
+          v
+        en50221 APDU (package)
+   --------------------------------------
+   |      |                             | High Level CI driver
+   |      |                             |
+   |      v                             |
+   |    en50221 APDU (unpackage)        |
+   |      |                             |
+   |      |                             |
+   |      v                             |
+   |    sanity checks                   |
+   |      |                             |
+   |      |                             |
+   |      v                             |
+   |    do (H/W dep)                    |
+   --------------------------------------
+          |    Hardware
+          |
+          v
+
+
+
+
+The High Level CI interface uses the EN50221 DVB standard, following a
+standard ensures futureproofness.