short.c

本源码是将述嵌入式LINUX驱动程序例程

};

void short_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
    struct timeval tv;
    int written;

    do_gettimeofday(&tv);

    /* Write a 16 byte record. Assume PAGE_SIZE is a multiple of 16 */
    written = sprintf((char *)short_head,"%08u.%06u\n",
                          (int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
    short_incr_bp(&short_head, written);
    wake_up_interruptible(&short_queue); /* awake any reading process */
}

/*
 * The following two functions are equivalent to the previous one,
 * but split in top and bottom half. First, a few needed variables
 */

#define NR_TIMEVAL 512 /* length of the array of time values */

struct timeval tv_data[NR_TIMEVAL]; /* too lazy to allocate it */
volatile struct timeval *tv_head=tv_data;
volatile struct timeval *tv_tail=tv_data;

static struct tq_struct short_task; /* 0 by now, filled by short_init code */

int short_bh_count = 0;

/*
 * Increment a circular buffer pointer in a way that nobody sees
 * an intermediate value.
 */
static inline void short_incr_tv(volatile struct timeval **tvp)
{
    if (*tvp == (tv_data + NR_TIMEVAL - 1))
        *tvp = tv_data;  /* Wrap */
    else
        (*tvp)++;
}



void short_do_tasklet (unsigned long unused)
{
    int savecount = short_bh_count, written;
    short_bh_count = 0; /* we have already been removed from the queue */
    /*
     * The bottom half reads the tv array, filled by the top half,
     * and prints it to the circular text buffer, which is then consumed
     * by reading processes
     */

    /* First write the number of interrupts that occurred before this bh */

    written = sprintf((char *)short_head,"bh after %6i\n",savecount);
    short_incr_bp(&short_head, written);

    /*
     * Then, write the time values. Write exactly 16 bytes at a time,
     * so it aligns with PAGE_SIZE
     */

    do {
        written = sprintf((char *)short_head,"%08u.%06u\n",
			(int)(tv_tail->tv_sec % 100000000),
			(int)(tv_tail->tv_usec));
	short_incr_bp(&short_head, written);
	short_incr_tv(&tv_tail);
    } while (tv_tail != tv_head);

    wake_up_interruptible(&short_queue); /* awake any reading process */
}


void short_bh_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
    /* cast to stop 'volatile' warning */
    do_gettimeofday((struct timeval *) tv_head);
    short_incr_tv(&tv_head);

    /* Queue the bh. Don't care for multiple enqueueing */
    queue_task(&short_task, &tq_immediate);
    mark_bh(IMMEDIATE_BH);

    short_bh_count++; /* record that an interrupt arrived */
}


#ifdef HAVE_TASKLETS
/*
 * Tasklet top half
 */

void short_tl_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
    do_gettimeofday((struct timeval *) tv_head); /* cast to stop 'volatile' warning */
    short_incr_tv(&tv_head);
    tasklet_schedule(&short_tasklet);
    short_bh_count++; /* record that an interrupt arrived */
}

#endif /* HAVE_TASKLETS */



void short_sh_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
    int value, written;
    struct timeval tv;

    /* If it wasn't short, return immediately */
    value = inb(short_base);
    if (!(value & 0x80)) return;
        
    /* clear the interrupting bit */
    outb(value & 0x7F, short_base);

    /* the rest is unchanged */

    do_gettimeofday(&tv);
    written = sprintf((char *)short_head,"%08u.%06u\n",
                          (int)(tv.tv_sec % 100000000), (int)(tv.tv_usec));
    short_incr_bp(&short_head, written);
    wake_up_interruptible(&short_queue); /* awake any reading process */
}

void short_kernelprobe(void)
{
    int count = 0;
    do {
        unsigned long mask;

        mask = probe_irq_on();
        outb_p(0x10,short_base+2); /* enable reporting */
        outb_p(0x00,short_base);   /* clear the bit */
        outb_p(0xFF,short_base);   /* set the bit: interrupt! */
        outb_p(0x00,short_base+2); /* disable reporting */
        udelay(5);  /* give it some time */
        short_irq = probe_irq_off(mask);

        if (short_irq == 0) { /* none of them? */
            printk(KERN_INFO "short: no irq reported by probe\n");
            short_irq = -1;
        }
        /*
         * if more than one line has been activated, the result is
         * negative. We should service the interrupt (no need for lpt port)
         * and loop over again. Loop at most five times, then give up
         */
    } while (short_irq < 0 && count++ < 5);
    if (short_irq < 0)
        printk("short: probe failed %i times, giving up\n", count);
}

void short_probing(int irq, void *dev_id, struct pt_regs *regs)
{
    if (short_irq == 0) short_irq = irq;    /* found */
    if (short_irq != irq) short_irq = -irq; /* ambiguous */
}

void short_selfprobe(void)
{
    int trials[] = {3, 5, 7, 9, 0};
    int tried[]  = {0, 0, 0, 0, 0};
    int i, count = 0;

     /*
      * install the probing handler for all possible lines. Remember
      * the result (0 for success, or -EBUSY) in order to only free
      * what has been acquired
      */
    for (i=0; trials[i]; i++)
        tried[i] = request_irq(trials[i], short_probing,
                               SA_INTERRUPT, "short probe", NULL);

    do {
        short_irq = 0; /* none got, yet */
        outb_p(0x10,short_base+2); /* enable */
        outb_p(0x00,short_base);
        outb_p(0xFF,short_base); /* toggle the bit */
        outb_p(0x00,short_base+2); /* disable */
        udelay(5);  /* give it some time */

        /* the value has been set by the handler */
        if (short_irq == 0) { /* none of them? */
            printk(KERN_INFO "short: no irq reported by probe\n");
        }
        /*
         * If more than one line has been activated, the result is
         * negative. We should service the interrupt (but the lpt port
         * doesn't need it) and loop over again. Do it at most 5 times
         */
    } while (short_irq <=0 && count++ < 5);

    /* end of loop, uninstall the handler */
    for (i=0; trials[i]; i++)
        if (tried[i] == 0)
            free_irq(trials[i], NULL);

    if (short_irq < 0)
        printk("short: probe failed %i times, giving up\n", count);
}

/* Two wrappers, to use non-page-aligned ioremap() on 2.0 */

/* Remap a not (necessarily) aligned port region */
void *short_remap(unsigned long phys_addr)
{
    /* The code comes mainly from arch/any/mm/ioremap.c */
    unsigned long offset, last_addr, size;

    last_addr = phys_addr + SHORT_NR_PORTS - 1;
    offset = phys_addr & ~PAGE_MASK;
    
    /* Adjust the begin and end to remap a full page */
    phys_addr &= PAGE_MASK;
    size = PAGE_ALIGN(last_addr) - phys_addr;
    return ioremap(phys_addr, size) + offset;
}

/* Unmap a region obtained with short_remap */
void short_unmap(void *virt_add)
{
    iounmap((void *)((unsigned long)virt_add & PAGE_MASK));
}



/* Finally, init and cleanup */

int short_init(void)
{
    int result;

    /*
     * first, sort out the base/short_base ambiguity: we'd better
     * use short_base in the code, for clarity, but allow setting
     * just "base" at load time. Same for "irq".
     */
    short_base = base;
    short_irq = irq;

    /* Set up owner pointers.*/
    SET_MODULE_OWNER(&short_fops);
    SET_MODULE_OWNER(&short_i_fops);

    /* Get our needed resources. */
    if (!use_mem) {
	result = check_region(short_base, SHORT_NR_PORTS);
	if (result) {
	    printk(KERN_INFO "short: can't get I/O port address 0x%lx\n",
		   short_base);
	    return result;
	}
	request_region(short_base, SHORT_NR_PORTS, "short");
    } else {
	result = check_mem_region(short_base, SHORT_NR_PORTS);
	if (result) {
	    printk(KERN_INFO "short: can't get I/O mem address 0x%lx\n",
		   short_base);
	    return result;
	}
	request_mem_region(short_base, SHORT_NR_PORTS, "short");

	/* also, ioremap it */
	short_phys = short_base;
	short_base = (unsigned long)short_remap(short_base);
	/* Hmm... we should check the return value */
    }
    result = register_chrdev(major, "short", &short_fops);
    if (result < 0) {
        printk(KERN_INFO "short: can't get major number\n");
        release_region(short_base,SHORT_NR_PORTS);
        return result;
    }
    if (major == 0) major = result; /* dynamic */

    short_buffer = __get_free_pages(GFP_KERNEL,0); /* never fails */
    short_head = short_tail = short_buffer;

    /*
     * Fill the short_task structure, used for the bottom half handler.
     * The cast is there to prevent warnings about the type of the
     * (unused) argument.
     */
    short_task.routine = (void (*)(void *)) short_do_tasklet;
    short_task.data = NULL; /* unused */

    /*
     * Now we deal with the interrupt: either kernel-based
     * autodetection, DIY detection or default number
     */

    if (short_irq < 0 && probe == 1)
        short_kernelprobe();

    if (short_irq < 0 && probe == 2)
        short_selfprobe();

    if (short_irq < 0) /* not yet specified: force the default on */
        switch(short_base) {
          case 0x378: short_irq = 7; break;
          case 0x278: short_irq = 2; break;
          case 0x3bc: short_irq = 5; break;
        }

    /*
     * If shared has been specified, installed the shared handler
     * instead of the normal one. Do it first, before a -EBUSY will
     * force short_irq to -1.
     */
    if (short_irq >= 0 && share > 0) {
        result = request_irq(short_irq, short_sh_interrupt,
                             SA_SHIRQ | SA_INTERRUPT,"short",
                             short_sh_interrupt);
        if (result) {
            printk(KERN_INFO "short: can't get assigned irq %i\n", short_irq);
            short_irq = -1;
        }
        else { /* actually enable it -- assume this *is* a parallel port */
            outb(0x10,short_base+2);
        }
        return 0; /* the rest of the function only installs handlers */
    }

    if (short_irq >= 0) {
        result = request_irq(short_irq, short_interrupt,
                             SA_INTERRUPT, "short", NULL);
        if (result) {
            printk(KERN_INFO "short: can't get assigned irq %i\n",
                   short_irq);
            short_irq = -1;
        }
        else { /* actually enable it -- assume this *is* a parallel port */
            outb(0x10,short_base+2);
        }
    }

    /*
     * Ok, now change the interrupt handler if using top/bottom halves
     * has been requested
     */
    if (short_irq >= 0 && (bh + tasklet) > 0) {
        free_irq(short_irq,NULL);
        result = request_irq(short_irq,
#ifdef HAVE_TASKLETS
                        tasklet ? short_tl_interrupt :
#endif
                        short_bh_interrupt,
                        SA_INTERRUPT,"short-bh", NULL);
        if (result) {
            printk(KERN_INFO "short-bh: can't get assigned irq %i\n",
                   short_irq);
            short_irq = -1;
        }
    }

    return 0;
}

void short_cleanup(void)
{
    if (short_irq >= 0) {
        outb(0x0, short_base + 2);   /* disable the interrupt */
        if (!share) free_irq(short_irq, NULL);
        else free_irq(short_irq, short_sh_interrupt);
    }
        
    unregister_chrdev(major, "short");
    if (use_mem) {
	short_unmap((void *)short_base);
	release_mem_region(short_base, SHORT_NR_PORTS);
    } else {
	release_region(short_base,SHORT_NR_PORTS);
    }
    if (short_buffer) free_page(short_buffer);
}

module_init(short_init);
module_exit(short_cleanup);