scsi.c

GNU Mach 微内核源代码, 基于美国卡内基美隆大学的 Mach 研究项目

	/* Obviously the bus reset didn't work.
	 * Let's try even harder and call for an HBA reset.
         * Maybe the HBA itself crashed and this will shake it loose.
	 */
	printk("SCSI host %d reset (pid %ld) timed out - trying to shake it loose\n",
	       SCpnt->host->host_no, SCpnt->pid);
	SCpnt->internal_timeout &= ~(IN_RESET | IN_RESET2);
	SCpnt->internal_timeout |= IN_RESET3;
        scsi_reset (SCpnt,
		    SCSI_RESET_ASYNCHRONOUS | SCSI_RESET_SUGGEST_HOST_RESET);
	return;
		
    default:
	printk("SCSI host %d reset (pid %ld) timed out again -\n",
	       SCpnt->host->host_no, SCpnt->pid);
	printk("probably an unrecoverable SCSI bus or device hang.\n");
	return;

    }
    
}


/* This function takes a quick look at a request, and decides if it
 * can be queued now, or if there would be a stall while waiting for
 * something else to finish.  This routine assumes that interrupts are
 * turned off when entering the routine.  It is the responsibility
 * of the calling code to ensure that this is the case. 
 */

Scsi_Cmnd * request_queueable (struct request * req, Scsi_Device * device)
{
    Scsi_Cmnd * SCpnt = NULL;
    int tablesize;
    Scsi_Cmnd * found = NULL;
    struct buffer_head * bh, *bhp;
    
    if (!device)
	panic ("No device passed to request_queueable().\n");
    
    if (req && req->rq_status == RQ_INACTIVE)
	panic("Inactive in request_queueable");

    /*
     * Look for a free command block.  If we have been instructed not to queue
     * multiple commands to multi-lun devices, then check to see what else is 
     * going for this device first.
     */
      
    if (!device->single_lun) {
	SCpnt = device->device_queue;
	while(SCpnt){
	    if(SCpnt->request.rq_status == RQ_INACTIVE) break;
	    SCpnt = SCpnt->device_next;
	}
    } else {
	SCpnt = device->host->host_queue;
	while(SCpnt){
	    if(SCpnt->channel == device->channel 
                && SCpnt->target == device->id) {
		if (SCpnt->lun == device->lun) {
		    if(found == NULL 
		       && SCpnt->request.rq_status == RQ_INACTIVE) 
		    {
			found=SCpnt;
		    }
		} 
		if(SCpnt->request.rq_status != RQ_INACTIVE) {
		    /*
		     * I think that we should really limit things to one
		     * outstanding command per device - this is what tends 
                     * to trip up buggy firmware.
		     */
		    return NULL;
		}
	    }
	    SCpnt = SCpnt->next;
	}
	SCpnt = found;
    }
    
    if (!SCpnt) return NULL;
    
    if (SCSI_BLOCK(device->host)) return NULL;
    
    if (req) {
	memcpy(&SCpnt->request, req, sizeof(struct request));
	tablesize = device->host->sg_tablesize;
	bhp = bh = req->bh;
	if(!tablesize) bh = NULL;
	/* Take a quick look through the table to see how big it is.  
	 * We already have our copy of req, so we can mess with that 
	 * if we want to. 
	 */
	while(req->nr_sectors && bh){
	    bhp = bhp->b_reqnext;
	    if(!bhp || !CONTIGUOUS_BUFFERS(bh,bhp)) tablesize--;
	    req->nr_sectors -= bh->b_size >> 9;
	    req->sector += bh->b_size >> 9;
	    if(!tablesize) break;
	    bh = bhp;
	}
	if(req->nr_sectors && bh && bh->b_reqnext){  /* Any leftovers? */
	    SCpnt->request.bhtail = bh;
	    req->bh = bh->b_reqnext; /* Divide request */
	    bh->b_reqnext = NULL;
	    bh = req->bh;
	    
	    /* Now reset things so that req looks OK */
	    SCpnt->request.nr_sectors -= req->nr_sectors;
	    req->current_nr_sectors = bh->b_size >> 9;
	    req->buffer = bh->b_data;
	    SCpnt->request.sem = NULL; /* Wait until whole thing done */
	} else {
	    req->rq_status = RQ_INACTIVE;
	    wake_up(&wait_for_request);
	}
    } else {
	SCpnt->request.rq_status = RQ_SCSI_BUSY;  /* Busy, but no request */
	SCpnt->request.sem = NULL;   /* And no one is waiting for the device 
				      * either */
    }
    
    SCpnt->use_sg = 0;               /* Reset the scatter-gather flag */
    SCpnt->old_use_sg  = 0;
    SCpnt->transfersize = 0;
    SCpnt->underflow = 0;
    SCpnt->cmd_len = 0;

/* Since not everyone seems to set the device info correctly
 * before Scsi_Cmnd gets send out to scsi_do_command, we do it here.
 */ 
    SCpnt->channel = device->channel;
    SCpnt->lun = device->lun;
    SCpnt->target = device->id;

    return SCpnt;
}

/* This function returns a structure pointer that will be valid for
 * the device.  The wait parameter tells us whether we should wait for
 * the unit to become free or not.  We are also able to tell this routine
 * not to return a descriptor if the host is unable to accept any more
 * commands for the time being.  We need to keep in mind that there is no
 * guarantee that the host remain not busy.  Keep in mind the
 * request_queueable function also knows the internal allocation scheme
 * of the packets for each device 
 */

Scsi_Cmnd * allocate_device (struct request ** reqp, Scsi_Device * device,
			     int wait)
{
    kdev_t dev;
    struct request * req = NULL;
    int tablesize;
    unsigned long flags;
    struct buffer_head * bh, *bhp;
    struct Scsi_Host * host;
    Scsi_Cmnd * SCpnt = NULL;
    Scsi_Cmnd * SCwait = NULL;
    Scsi_Cmnd * found = NULL;
    
    if (!device)
	panic ("No device passed to allocate_device().\n");
    
    if (reqp) req = *reqp;
    
    /* See if this request has already been queued by an interrupt routine */
    if (req) {
	if(req->rq_status == RQ_INACTIVE) return NULL;
	dev = req->rq_dev;
    } else
        dev = 0;		/* unused */
    
    host = device->host;
    
    if (intr_count && SCSI_BLOCK(host)) return NULL;
    
    while (1==1){
	if (!device->single_lun) {
	    SCpnt = device->device_queue;
	    while(SCpnt){
		SCwait = SCpnt;
		if(SCpnt->request.rq_status == RQ_INACTIVE) break;
		SCpnt = SCpnt->device_next;
	    }
	} else {
	    SCpnt = device->host->host_queue;
	    while(SCpnt){
		if(SCpnt->channel == device->channel 
                   && SCpnt->target == device->id) {
		    if (SCpnt->lun == device->lun) {
			SCwait = SCpnt;
			if(found == NULL 
			   && SCpnt->request.rq_status == RQ_INACTIVE) 
			{
			    found=SCpnt;
			}
		    } 
		    if(SCpnt->request.rq_status != RQ_INACTIVE) {
			/*
			 * I think that we should really limit things to one
			 * outstanding command per device - this is what tends
                         * to trip up buggy firmware.
			 */
			found = NULL;
			break;
		    }
		}
		SCpnt = SCpnt->next;
	    }
	    SCpnt = found;
	}

	save_flags(flags);
	cli();
	/* See if this request has already been queued by an interrupt routine
	 */
	if (req && (req->rq_status == RQ_INACTIVE || req->rq_dev != dev)) {
	    restore_flags(flags);
	    return NULL;
	}
	if (!SCpnt || SCpnt->request.rq_status != RQ_INACTIVE)	/* Might have changed */
	{
#if 1	/* NEW CODE */
		if (wait && SCwait && SCwait->request.rq_status != RQ_INACTIVE){
 			sleep_on(&device->device_wait);
 			restore_flags(flags);
	 	} else {
 			restore_flags(flags);
	 		if (!wait) return NULL;
 			if (!SCwait) {
	 			printk("Attempt to allocate device channel %d,"
                                       " target %d, lun %d\n", device->channel,
                                       device->id, device->lun);
 				panic("No device found in allocate_device\n");
	 		}
 		}
#else	/* ORIGINAL CODE */
		    restore_flags(flags);
		    if(!wait) return NULL;
		    if (!SCwait) {
			printk("Attempt to allocate device channel %d, target"
                               " %d, lun %d\n", device->channel, device->id, 
                               device->lun);
			panic("No device found in allocate_device\n");
		    }
		    SCSI_SLEEP(&device->device_wait,
			       (SCwait->request.rq_status != RQ_INACTIVE));
#endif
	} else {
	    if (req) {
		memcpy(&SCpnt->request, req, sizeof(struct request));
		tablesize = device->host->sg_tablesize;
		bhp = bh = req->bh;
		if(!tablesize) bh = NULL;
		/* Take a quick look through the table to see how big it is.  
		 * We already have our copy of req, so we can mess with that 
		 * if we want to.  
		 */
		while(req->nr_sectors && bh){
		    bhp = bhp->b_reqnext;
		    if(!bhp || !CONTIGUOUS_BUFFERS(bh,bhp)) tablesize--;
		    req->nr_sectors -= bh->b_size >> 9;
		    req->sector += bh->b_size >> 9;
		    if(!tablesize) break;
		    bh = bhp;
		}
		if(req->nr_sectors && bh && bh->b_reqnext){/* Any leftovers? */
		    SCpnt->request.bhtail = bh;
		    req->bh = bh->b_reqnext; /* Divide request */
		    bh->b_reqnext = NULL;
		    bh = req->bh;
		    /* Now reset things so that req looks OK */
		    SCpnt->request.nr_sectors -= req->nr_sectors;
		    req->current_nr_sectors = bh->b_size >> 9;
		    req->buffer = bh->b_data;
		    SCpnt->request.sem = NULL; /* Wait until whole thing done*/
		}
		else
		{
		    req->rq_status = RQ_INACTIVE;
		    *reqp = req->next;
		    wake_up(&wait_for_request);
		}
	    } else {
		SCpnt->request.rq_status = RQ_SCSI_BUSY;
		SCpnt->request.sem = NULL;   /* And no one is waiting for this 
					      * to complete */
	    }
	    restore_flags(flags);
	    break;
	}
    }
    
    SCpnt->use_sg = 0;            /* Reset the scatter-gather flag */
    SCpnt->old_use_sg  = 0;
    SCpnt->transfersize = 0;      /* No default transfer size */
    SCpnt->cmd_len = 0;

    SCpnt->underflow = 0;         /* Do not flag underflow conditions */

    /* Since not everyone seems to set the device info correctly
     * before Scsi_Cmnd gets send out to scsi_do_command, we do it here.
     */ 
    SCpnt->channel = device->channel;
    SCpnt->lun = device->lun;
    SCpnt->target = device->id;

    return SCpnt;
}

/*
 * This is inline because we have stack problemes if we recurse to deeply.
 */

inline void internal_cmnd (Scsi_Cmnd * SCpnt)
{
    unsigned long flags, timeout;
    struct Scsi_Host * host;
#ifdef DEBUG_DELAY
    unsigned long clock;
#endif

#if DEBUG
    unsigned long *ret = 0;
#ifdef __mips__
    __asm__ __volatile__ ("move\t%0,$31":"=r"(ret));
#else
   ret =  __builtin_return_address(0);
#endif
#endif
    
    host = SCpnt->host;
    
    save_flags(flags);
    cli();
    /* Assign a unique nonzero serial_number. */
    if (++serial_number == 0) serial_number = 1;
    SCpnt->serial_number = serial_number;

    /*
     * We will wait MIN_RESET_DELAY clock ticks after the last reset so
     * we can avoid the drive not being ready.
     */
    timeout = host->last_reset + MIN_RESET_DELAY;
    if (jiffies < timeout) {
	int ticks_remaining = timeout - jiffies;
	/*
	 * NOTE: This may be executed from within an interrupt
	 * handler!  This is bad, but for now, it'll do.  The irq
	 * level of the interrupt handler has been masked out by the
	 * platform dependent interrupt handling code already, so the
	 * sti() here will not cause another call to the SCSI host's
	 * interrupt handler (assuming there is one irq-level per
	 * host).
	 */
	sti();
	while (--ticks_remaining >= 0) udelay(1000000/HZ);
	host->last_reset = jiffies - MIN_RESET_DELAY;
    }
    restore_flags(flags);
    
    update_timeout(SCpnt, SCpnt->timeout_per_command);
    
    /*
     * We will use a queued command if possible, otherwise we will emulate the
     * queuing and calling of completion function ourselves.
     */
#ifdef DEBUG
    printk("internal_cmnd (host = %d, channel = %d, target = %d, "
	   "command = %p, buffer = %p, \nbufflen = %d, done = %p)\n", 
	   SCpnt->host->host_no, SCpnt->channel, SCpnt->target, SCpnt->cmnd, 
	   SCpnt->buffer, SCpnt->bufflen, SCpnt->done);
#endif
    
    if (host->can_queue)
    {
#ifdef DEBUG
	printk("queuecommand : routine at %p\n",
	       host->hostt->queuecommand);
#endif
	/* This locking tries to prevent all sorts of races between
	 * queuecommand and the interrupt code.  In effect,
	 * we are only allowed to be in queuecommand once at
	 * any given time, and we can only be in the interrupt
	 * handler and the queuecommand function at the same time
	 * when queuecommand is called while servicing the
	 * interrupt. 
	 */
	
	if(!intr_count && SCpnt->host->irq)
	    disable_irq(SCpnt->host->irq);
	
	host->hostt->queuecommand (SCpnt, scsi_done);
	
	if(!intr_count && SCpnt->host->irq)
	    enable_irq(SCpnt->host->irq);
    }
    else
    {
	int temp;

#ifdef DEBUG
	printk("command() :  routine at %p\n", host->hostt->command);
#endif
	temp = host->hostt->command (SCpnt);
	SCpnt->result = temp;
#ifdef DEBUG_DELAY
	clock = jiffies + 4 * HZ;
	while (jiffies < clock) barrier();
	printk("done(host = %d, result = %04x) : routine at %p\n", 
	       host->host_no, temp, host->hostt->command);
#endif
	scsi_done(SCpnt);
    }
#ifdef DEBUG
    printk("leaving internal_cmnd()\n");
#endif
}

static void scsi_request_sense (Scsi_Cmnd * SCpnt)
{
    unsigned long flags;
    
    save_flags(flags);
    cli();
    SCpnt->flags |= WAS_SENSE | ASKED_FOR_SENSE;
    update_timeout(SCpnt, SENSE_TIMEOUT);
    restore_flags(flags);
    
    
    memcpy ((void *) SCpnt->cmnd , (void *) generic_sense, 
	    sizeof(generic_sense));
    
    SCpnt->cmnd[1] = SCpnt->lun << 5;
    SCpnt->cmnd[4] = sizeof(SCpnt->sense_buffer);
    
    SCpnt->request_buffer = &SCpnt->sense_buffer;
    SCpnt->request_bufflen = sizeof(SCpnt->sense_buffer);
    SCpnt->use_sg = 0;
    SCpnt->cmd_len = COMMAND_SIZE(SCpnt->cmnd[0]);
    internal_cmnd (SCpnt);
}