sim client

hi, i like to write the sim client protocol. i do not mean the code of the "sim reader" which is part of layer1 inside the phone. before i start, i would like to know what you think about my api idea. the api is not the low-level api between layer1 and the mobile application (APDU layer). it describes a higher layer for application or protocol processes which need to request IMSI, do key generation, or store location area information. one important thing is that different processes must be able request "read", "write", or other operations like key generation simultaniously. in order to handle multiple requests after each other, a queue inside sim client must exist. afterwar processing each request, the result must be sent only to the requesting process (if it still exists). a state machine watches over the current DF (current selected file area of the sim) and changes current "DF" if required, before processing read or write job. also it triggers the next job in the queue, if finished with the current one. int handle = sim_open(void (*cb)(...)) will add a new user instance. cb is the function to be called for response, handle is a unique id of the process (not a memory pointer, unique at all times after starting phone). void sim_job(struct msgb *msg) struct sim_job_hdr { int handle; uint8_t job_type; uint16_t file; }; will add a new job. the type defines the job type. examples are "READ" "WRITE" or "GSMKEY" requests. the handle is used to assign the read/write job to an instance. the file is used to select the correct data file of the sim. the data and len represent the data to be written. void cb(struct msgb *msg) is called back by the sim client when job is done. the handle is given, so multiple user instances may use the same callback. void sim_close(int handle) will remove user instance. outstanding jobs will finish, but no result is given, because cb is now unregistered. the coding and decoding of SIM files must be done by the application or protocol layer that use the sim client. andreas