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diff --git a/Documentation/userspace-api/media/dvb/ca_high_level.rst b/Documentation/userspace-api/media/dvb/ca_high_level.rst new file mode 100644 index 000000000..a73f3691c --- /dev/null +++ b/Documentation/userspace-api/media/dvb/ca_high_level.rst @@ -0,0 +1,157 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The High level CI API +===================== + +.. note:: + + This documentation is outdated. + +This document describes the high level CI API as in accordance to the +Linux DVB API. + + +With the High Level CI approach any new card with almost any random +architecture can be implemented with this style, the definitions +inside the 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 accommodate 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: + +.. code-block:: c + + 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 +accommodate 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) + + +On querying the device, the device yields information thus: + +.. code-block:: none + + 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. + +.. code-block:: c + + /* 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, + +.. code-block:: none + + 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. |