CS 450
Contents
1. WRITE CLEAR GOTOXY if the op_code is any of these values call your IO Scheduler to handle the interrupt I O Initialization e You need to create and initialize the IOCB s for the terminal and com_port devices e You need to open the terminal and com_port devices o trm_open POINTER TO THE IOCB EVENT FLAG com_open POINTER TO THE IOCB EVENT FLAG baud_rate Set the baud rate 1200 2 By passing a pointer to the event_flag this allows the terminal and com interrupt handlers to directly modify the event_flag I O Cleanup e When MPX is terminated Close the devices by calling trm_close and com close o Clear the waiting queues free the memory of any IOD s in the queue 2 Free the memory for the IOCB for each device Main Your main should do the following now iL 2 eS Se ae 9 sys__init MODULE_F Call Init functions you might have already written init functions in R2 and R3 that do the following sys_set_vec needs called initialize DCBs IOCBs initialize PCB ready blocked queues Open device drivers Install command handler as a process Load IDLE Call dispatcher this should run your comhan Close device drivers Other cleanup you might have cleanup functions in R2 and R3 to call Make sure the queues get cleared and all allocated memory is de allocated sys_exit Test Processes e Available on my website e Load these using your load function to test your project e CPUTERM A process which repeated2. keep track of in the IOCB o event_flag int will hold the current event_flag for the device o count int number of IOD s in the queue o head iod pointer to the first IOD in the waiting queue o tail iod pointer to the last IOD in the waiting queue e You will maintain the waiting queues in first in first out order I O Operations e You will need to download and link with your project TRMDRIVE C and TRMDRIVE H these are the functions for the TERMINAL driver You can open the files to see the parameters the functions take Make sure to include TRMDRIVE H and link TRMDRIVE C They will be available on my website e The following table illustrates what functions to call for which I O operations he COM_PORT functions come from your R5 check TRMDRIVE C and H for more specifics on the TERMINAL functions D _ Processing an I O Request e In both sys_call and the I O Scheduler it will be necessary to process an I O Request Here is the basic outline of how you would do that Decode the request from the IOD gt request for the operation at the head of the queue it will either be READ WRITE CLEAR GOTOXY e You will now need to call the appropriate function to handle the request The parameters are the same if you are calling a read or write trm_read for example 10 _FUNCTION com_iocb head gt buf_addr com_iocb head gt count_addr Call the appropriate operation using the syntax above to
3. to the parameter op_code e Ifthe waiting queue for that device is empty count o Insert the new IOD into the waiting queue as the head and tail set count 1 a m the request immediately refer to the slide on processing I O requests on how to o this e If waiting queue for that device is not empty 2 Insert the new IOD into the waiting queue at the tail e Block the process and return I O Completion e Every time sys_call is invoked it will need to check if any I O operations have been completed e Sys_call will do this by checking the event flags in each IOCB if it is set some completion steps need to be performed Sys_call modifications Call trm_getc this will flush the DOS keyboard buffer into the MPX buffer For each I O device COM_PORT and TERMINAL a Check if the event_flag is set 1 If the flag is set Clear the IOCB s event_flag set o Remove the IOD at the head of the IOCB s waiting queue and free the IOD s memory Unblock the process who had requested the IOD you just freed this should put it in the ready queue The process that requested the IOD is maintained as a field in the IOD Process the next I O request for that device e Se alo to perform these steps after you switch to the system temporary stack and before you reset COP s stack top pointer At the end of sys_ call where you currently check the op_ code to see if it is IDLE or EXIT you need to add checks for READ
4. CS 450 Module R6 Next Week e R5 is due next Friday No documentation no source code due R5 is stand alone so I will not be checking errors from previous modules But in R6 everything needs to work Note Dates marked will be determined R6 e Due at the time of your group s oral exam e Documentation due at the oral exam o o o o Programmer s Manual User s Manual but not the temporary commands manual Group Portfolio A complete copy of your source code Iwill check that you have included the comments that are required and you will lose points if they are missing e Turn in these documents bound in some fashion either a three ring binder or whatever method you want but do not just staple them for this module they must be bound Also you must turn in a CD with all of your source code including help files as well as your rogrammer s manual and user s manual Also please include a README file with the ollowing information on the CD Group number and group member names and semester Compiler and version number you used Operating System used for development If you used a DOS emulator DosBox or not Any other information that might be needed to run your MPX project e You will need to use the serial port emulator or two computers physically connected to demonstrate R6 just like R5 Oral Exams e Oral exams will take place during dead week On we will sc
5. handle the request Check the chart on the I O operations slide for information on which function to call Note that CLEAR and GOTOXY for the TERMINAL device require different parameters than those listed above I O Scheduler e The I O scheduler is a function you will write that will process a new I O request You will recall that in R3 you used a pointer to parameters that were pushed on the stack when an interrupt was generated we will need to access those parameters again Because of this it makes your coding very convenient if you place the I O Scheduler in your R3 C file and place the IOD and IOCB structs in R3 H It also makes it very convenient if you make your parameter that you used in R3 global if you haven t already If you make the parameter global you will not need to pass any parameters to your IO Scheduler In short the I O scheduler will create a new IOD for the I O request and either run it if the device is ready or place it in the waiting queue to be run later I O Scheduler Outline e Check which device is being requested stored in the device_id of the parameters e Create an IOD for the new request allocate space using sys_alloc_mem Set the PCB in the IOD to COP and set the name gt The COP is the process making the I O request so you need to save that in the IOD Set the buffer address to the parameter buf_addr and count address to the parameter count_addr and the request
6. hedule the oral exams make sure one group member comes so you can schedule your oral exam If no one from your group shows up on to schedule your group s oral y sr PY A y group rst ava exam takes place on the ilable day during dead week NO EXCEPTIONS e A poup members must attend the Oral Exam if you do not attend you will FAIL the class e The oral exam will last approximately one hour and will be comprised of R6 demonstration and questions from Dr Mooney and myself regarding the MPX project You are expected to know A e about every portion of the project including how you implemented specific things and nar Toa functions are needed even if you didn t work on that particular part o e You will find it VERY useful to bring a complete copy of your source code for each group member to the oral exam It is also helpful if you include a table of contents and tabs for each module so you can find specific functions quickly to answer questions R6 Overview e We need to implement continuous dispatch Comhan will be loaded as a process o An IDLE process will be introduced so there is always something in the ready queue and ready to dispatch e We will also need to provide more support for I O Requests An I O scheduler and completion handler will be added to handle I O events o Support for the terminal driver provided in the support software will be added Commands e At this point only the permanent co
7. ly displays a message line on the display screen This process is CPU bound it waits for a while in a loop between messages consuming processor time It runs continuously until terminated e CPUCOM Similar to CPUTERM but this process outputs its messages to the communication port We assume that a standard terminal or a separate PC or workstation running terminal emulation software is connected to this port e IOTERM Similar to CPUTERM but this process includes no delay loop It attempts to continuously output messages making a new request as soon as the last one has been PTE e IOCOM Similar to IOTERM but this process outputs its messages to the communications port e IOTRM25 Similar to IOTERM however this process displays its normal message exactly 25 times then requests termination A special message is displayed before the termination request If the process is dispatched after its termination request an error message is displayed and the process restarts e IOCOM25 Similar to IOTRM25 but this process outputs all of its messages to the serial port e IOMULTI Takes input from the com port and prints it to the screen Preliminary Code e On you must turn in preliminary code for R6 I want to see that you are starting on the code have coded the section where Comhan gets loaded as a process and you are making progress towards the I O scheduler Your code does not have to work or even compile e My intention is to fo
8. mmands should be in your system Commands that should be available in all temporary commands should be Set get date disabled Display MPX files e Commands that are temporary and Help should be removed Load 2 Block Quit Exit e Unblock Suspend Loading the R3 test processes Resume Dispatch Terminate a Create PCB Set Priority Delete PCB Show all blocked ready specific PCB Version Any commands relating to extra credit Do not allow users to suspend resume terminate or change the priority of SYSTEM processes Comhan and IDLE e In order to obtain continuous dispatch we will need to load comhan and an idle process into the ready queue when MPX starts e Comhan Whatever your procedure name is that handles your commands the one that prompts the user for a command and receives it needs to be installed as a process in MAIN Do this the same way you loaded the test processes in R3 Give Comhan the highest priority place it in the ready not suspended state insert it into the ready queue You may find it necessary to give Comhan a larger stack space than other processes minimum recommended stack size for Comhan is 4K When comhan gets the exit command it should remove all processes from the queues including IDLE and itself so that when dispatch is run again it detects an empty ready queue and returns to main e IDLE available on my website Load idle use your load functio
9. n from R4 Give IDLE the LOWEST priority Make sure IDLE is designated a SYSTEM process Resume it and put it in the ready queue o IDLE doesn t do anything it just ensures there is always a process in the ready queue and thus dispatcher won t quit until we want it to I O Event Handling e The basic idea here is this while an I O device is carrying out an I O request and a process is waiting on the I O request another process ah be allowed to execute have control of the PU e We will need to add functionality that allows us to queue I O requests by device and start an I O operation and run another process e We will also need to implement a way to handle the completion of an I O operation Handling I O Events e Devices Com Port driver written by you in R5 Terminal driver supplied on my website Data Structures JO Control Block IOCB holds information about an I O device IO Request Descriptor IOD holds information about an I O request I O Scheduler Processes I O requests either by processing immediately if the device is free or by placing it on the device s waiting queue if the device is busy Itis most convenient to put your I O scheduler and all related data structures in your R3 files e Sys_call Each time sys_call is invoked it will check to see if any I O events have been completed if so COP must be switched from the blocked to ready state and moved from the blocked to ready que
10. rce you to start working on R6 early and get the code written so you have 2 weeks to dedicate just to debugging e Code is due at the beginning of the project session on You may print out the appropriate sections of code and hand it in or email me a copy of your source code e If you turn in the preliminary code on you lose no points you lose 7 point 2 you lose 14 points Ifyou fail to turn in by you lose 20 points Tips You Gant use any I O device before you call trm_open and com_open this includes using printt Once you change sys_init to MODULE_F MPX will only work if your I O scheduler works Remember that you have up to 3 extra credit points available to you some of these are very simple to implement Change prompt history aliasing accepting commands from a script batch file Your programmer s manual should have documentation for every function in your code and every structure in your code Your user s manual should only have documentation for all permanent commands Documentation will be graded more thoroughly than previous attempts All functionality of MPX will be tested again so make sure everything works Make sure to thoroughly test your project crashes in particular will reflect poorly in your grade Make sure you have descriptive error messages displayed anytime there is an error Make sure that help is there for all permanent commands Make sure you implement paging for help sho
11. ue Active IOCB device must be cleared to signal that no request is active for the device Search the waiting queue for another process waiting to use the device that was just freed If one is found the I O scheduler is called to start the I O I O Request Descriptors IOD e We need to keep track of certain information for every active or pending I O request e Two options for where to put the IOD s An MPX process can only have 1 pending I O request at a time so it is possible to embed an IOD in each PCB However this is not very convenient when it comes time to find the next I O operation to be run Create a waiting queue of IOD s for each device much more convenient and I will assume you use this option in the remaining slides e Suggested information to keep track of Name of the process PCB requesting the I O operation char Pointer to the PCB requesting the I O operation Request type what kind of I O request i e IDLE READ WRITE CLEAR int Location of the transfer buffer char 2 Pointer to the count variable of the buffer int Pointer to the next IOD in the waiting queue Note that the request type transfer buffer and count variable refer to the op_code buffer_address and count_address in the parameter you use in R3 I O Control Block IOCB e Each device needs a control structure which will keep track of the waiting queue and current status e Suggested information you need to
12. w and anywhere else it is appropriate The R6 project manual will be available on my website as always reading it will make this module easier to complete For Module R6 do not use anything from Dr Mooney s site it is not in sync with the R6 you are doing this semester
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