[Manrix-devel] TIPS on how to write Services and Drivers in ManRiX.

[Manish R. <reg...@gm...>]

The code below (with heavy documentation) teaches you how to write
system services and device drivers in Manrix. Remember they all are
User Land Processes. they are also available in manrix/server/
If you have any questions/suggestions, drop a mail.

/* server_skeleton.c */
/*
 * This is the sample skeleton server.
 * This shows how you can implement a server (or System service)
 * in ManRiX.
 */

#include <mrx/svrpool.h>


/*
 * This Macro defines how many threads to create in advance.
 * We have implemented a pool of threads that works on Requests.
 * They are also called worker Threads.
 */
#define MAX_SVR_THREADS		5

/*
 * This is a Macro that tells which signal to use for notifying
 * Worker threads on arrival of request.
 */
#define SVR_REQUEST		SIGRTMIN


/*
 * a structure to hold pool struture.
 * see mrx/svrpool.h of LIBC.
 */
struct thrpool svrpool = {0};

/*
 * a function pointer type for functions which is called
 * according to Client Request
 */
typedef int (* fptr_t)(message_t );

/*
 * Functions to handle request
 */

int msg_no_func(message_t msg)
{
	return 0;
}

int msg_svr_open(message_t msg)
{
	return 0;
}

int msg_svr_close(message_t msg)
{
	return 0;
}

int msg_svr_read(message_t msg)
{
	return 0;
}

int msg_svr_write(message_t msg)
{
	return 0;
}

/*
 * address of functions according to request number.
 * Suppose, if the client calls for service 3 ( Remember message
 * passing is only way of doing server requests in ManRiX,
 * msg->w1 can be the reqest number though not necessarily),
 * msg_svr_read is called.
 */
fptr_t svr_func[] = {
	msg_no_func,
	msg_svr_open,
	msg_svr_close,
	msg_svr_read,
	msg_svr_write,
};

/*
 * This is an Alternative worker.
 * Only used when the pool is full.
 */
void *worker(poolstruct_t pool)
{
	fptr_t ptr;

	ptr = svr_func[pool->request];
	ptr(&pool->msg);

	return NULL;
}

/*
 * This is an alternative message handler.
 * It is called only when all pools are used.
 * It simply creates a thread and calls the worker
 */
void handle_full(void *ptr)
{
	pthread_attr_t attr;
	struct sched_param parm;
	poolstruct_t thr;

	thr = (poolstruct_t)malloc(sizeof(struct poolstruct));

	if(thr == NULL)
		return ;

	pthread_attr_init(&attr);
	parm.sched_priority = PRIO_SYS_DEF;
	pthread_attr_setschedparam(&attr, &parm);
	pthread_create(&thr->owner_id, &attr, (pthtype_t)worker, thr);
}

/*
 * The worker thread function. All threads in the pool
 * gets here and waits for the arrival of request.
 * After the arrival of the request, call the function
 * according to the request number.
 */
void *svr_worker(poolstruct_t pool)
{
	sigset_t set;
	struct sigaction action;
	int num, off;
	fptr_t ptr;

	/*
	 * Just respond to the particular signal used to notify
	 * worker thread. Not other signals.
	 */
	sigfillset(&set);
	sigdelset(&set, SVR_REQUEST);
	pthread_sigmask(SIG_SETMASK, &set, NULL);

	/*
	 * Just ignore the the signal.
	 * It will simply wake the thread on signal arrival.
	 */
	action.sa_handler = SIG_IGN;
	sigaction(SVR_REQUEST, &action, NULL);

	pool->flag |= POOL_DONE;

	/*
	 * Just to know which thread in the bitmap we are using
	 * Later we will mark it busy.
	 */
	off = ((unsigned long)pool - (unsigned
long)svrpool.pool)/sizeof(struct poolstruct);

 	/*
 	 * If you are using Previledged instructions (eg in/out, cli etc.).
 	 */
 	syscall_change_iopl(3);

	while(1)
	{
		/*
		 * Wait for the signal.
		 * i.e. the arrival of request
		 */
		sigwait(&set, &num);

		/*
		 * Call the appropriate function according to request number.
		 */
		ptr = con_func[pool->request];
		ptr(&pool->msg);

		/*
		 * Clear the bitmap to mark it busy
		 */
		clear_bit(&svrpool.pool_bitmap, off);
	}
}

/* Main: */
int main(int argc, char *argv)
{

	/*
	 * You Must use this syscall if your server uses
	 * Previledged instructions (eg in/out, cli etc.).
	 * This raises the I/O previdge level of the calling thread
	 * to 3.
	 */
	syscall_change_iopl(3);

	/*
	 * You can specify the alternative handler
	 * They will be used in case all the threads
	 * in the pool is used.
	 */
	svrpool.altworker = (pthtype_t)handle_full;

	/*
	 * Initialize bitmap to 0. So, in ia32, up to 32 threads can be
	 * used (for now). 0 means free thread, 1 means used thread.
	 */
	svrpool.pool_bitmap = 0;

	/*
	 * Initialize the thread pool.
	 */
	ret = pool_init(&svrpool, MAX_SVR_THREADS, (pthtype_t)svr_worker);
	if(ret < 0)
		printf("Pool Failed");

	/*
	 * Infinite loop where the thread listens to the request.
	 * After the request arrives, the worker thread runs.
	 */
	msg_loop(&svrpool, SVR_REQUEST);

	return 0;
}

/* driver skeleton.c */
/*
 * This is the sample skeleton driver.
 * This shows how you can implement a driver as a seperate process
 * (or System service) in ManRiX.
 */
#include <pthread.h>
#include <sched.h>
#include <mrx/svrpool.h>
#include <asm/syscall.h>

/* The interrupt Entry */
void intr()
{
	// Handle the interrupt here
}

/*
 * The Device Interrupt handler thread entry
 */
void *kbd_thr(void *data)
{
	int ret;
	/*
	 * You Must use this syscall if your driver uses
	 * Previledged instructions (eg in/out, cli etc.).
	 * This raises the I/O previdge level of the calling thread
	 * to 3. Required in Most cases.
	 */
	syscall_change_iopl(3);

	/*
	 * Make Sure you enable the IRQ in 8259a chips (in x86)
	 */
	IRQ_init(IRQNO);

	/*
	 * Request for the IRQ.
	 * This syscall hooks the function intr() to irq IRQNO
	 * That function is called on each Interrupt.
	 */
	syscall_IRQ_request(IRQNO, intr);

	do{
		/*
		 * This function waits for the IRQ.
		 */
		ret = syscall_IRQ_wait();

	}while(1 == 1);

	return NULL;
}


/* Initialize the driver */

/* Use main if required i.e main does not exist previously */
/* int main() */

int drv_init()
{
	pthread_attr_t attr;
	struct sched_param parm;

	/*
	 * You can use the same thread or create a seperate thread
	 * for listening to interrupts.
	 * Give maximum priority (but not a must).
	 */
	pthread_attr_init(&attr);
	parm.sched_priority = PRIO_RT_MAX;
	pthread_attr_setschedparam(&attr, &parm);

	pthread_create(NULL, &attr, drv_thr, NULL);

	return 0;
}


regards
Manish Regmi