pd.c

讲述linux的初始化过程

		while ((j < PD_NAMELEN-2) && (PD.name[j]=name[j])) j++;
		PD.name[j++] = 'a' + unit;
		PD.name[j] = 0;
		PD.alt_geom = DU[D_GEO];
		PD.standby = DU[D_SBY];
		if (DU[D_PRT]) pd_drive_count++;
	}
}

static inline int pd_new_segment(request_queue_t *q, struct request *req, int max_segments)
{
	if (max_segments > cluster)
		max_segments = cluster;

	if (req->nr_segments < max_segments) {
		req->nr_segments++;
		q->elevator.nr_segments++;
		return 1;
	}
	return 0;
}

static int pd_back_merge_fn(request_queue_t *q, struct request *req, 
			    struct buffer_head *bh, int max_segments)
{
	if (req->bhtail->b_data + req->bhtail->b_size == bh->b_data)
		return 1;
	return pd_new_segment(q, req, max_segments);
}

static int pd_front_merge_fn(request_queue_t *q, struct request *req, 
			     struct buffer_head *bh, int max_segments)
{
	if (bh->b_data + bh->b_size == req->bh->b_data)
		return 1;
	return pd_new_segment(q, req, max_segments);
}

static int pd_merge_requests_fn(request_queue_t *q, struct request *req,
				struct request *next, int max_segments)
{
	int total_segments = req->nr_segments + next->nr_segments;
	int same_segment;

	if (max_segments > cluster)
		max_segments = cluster;

	same_segment = 0;
	if (req->bhtail->b_data + req->bhtail->b_size == next->bh->b_data) {
		total_segments--;
		same_segment = 1;
	}
    
	if (total_segments > max_segments)
		return 0;

	q->elevator.nr_segments -= same_segment;
	req->nr_segments = total_segments;
	return 1;
}

int pd_init (void)

{       int i;
	request_queue_t * q; 

	if (disable) return -1;
        if (devfs_register_blkdev(MAJOR_NR,name,&pd_fops)) {
                printk("%s: unable to get major number %d\n",
                        name,major);
                return -1;
        }
	q = BLK_DEFAULT_QUEUE(MAJOR_NR);
	blk_init_queue(q, DEVICE_REQUEST);
	q->back_merge_fn = pd_back_merge_fn;
	q->front_merge_fn = pd_front_merge_fn;
	q->merge_requests_fn = pd_merge_requests_fn;
        read_ahead[MAJOR_NR] = 8;       /* 8 sector (4kB) read ahead */
        
	pd_gendisk.major = major;
	pd_gendisk.major_name = name;
	pd_gendisk.next = gendisk_head;
	gendisk_head = &pd_gendisk;

	for(i=0;i<PD_DEVS;i++) pd_blocksizes[i] = 1024;
	blksize_size[MAJOR_NR] = pd_blocksizes;

	printk("%s: %s version %s, major %d, cluster %d, nice %d\n",
		name,name,PD_VERSION,major,cluster,nice);
	pd_init_units();
	pd_valid = 0;
	pd_gendisk.nr_real = pd_detect();
	pd_valid = 1;

#ifdef MODULE
        if (!pd_gendisk.nr_real) {
		cleanup_module();
		return -1;
	}
#endif
        return 0;
}

static int pd_open (struct inode *inode, struct file *file)

{       int unit = DEVICE_NR(inode->i_rdev);

        if ((unit >= PD_UNITS) || (!PD.present)) return -ENODEV;

        MOD_INC_USE_COUNT;

	wait_event (pd_wait_open, pd_valid);

        PD.access++;

        if (PD.removable) {
		pd_media_check(unit);
		pd_doorlock(unit,IDE_DOORLOCK);
	}
        return 0;
}

static int pd_ioctl(struct inode *inode,struct file *file,
                    unsigned int cmd, unsigned long arg)

{       struct hd_geometry *geo = (struct hd_geometry *) arg;
        int dev, err, unit;

        if ((!inode) || (!inode->i_rdev)) return -EINVAL;
        dev = MINOR(inode->i_rdev);
	unit = DEVICE_NR(inode->i_rdev);
        if (dev >= PD_DEVS) return -EINVAL;
	if (!PD.present) return -ENODEV;

        switch (cmd) {
	    case CDROMEJECT:
		if (PD.access == 1) pd_eject(unit);
		return 0;
            case HDIO_GETGEO:
                if (!geo) return -EINVAL;
                err = verify_area(VERIFY_WRITE,geo,sizeof(*geo));
                if (err) return err;

		if (PD.alt_geom) {
                    put_user(PD.capacity/(PD_LOG_HEADS*PD_LOG_SECTS), 
		    		(short *) &geo->cylinders);
                    put_user(PD_LOG_HEADS, (char *) &geo->heads);
                    put_user(PD_LOG_SECTS, (char *) &geo->sectors);
		} else {
                    put_user(PD.cylinders, (short *) &geo->cylinders);
                    put_user(PD.heads, (char *) &geo->heads);
                    put_user(PD.sectors, (char *) &geo->sectors);
		}
                put_user(pd_hd[dev].start_sect,(long *)&geo->start);
                return 0;
            case BLKGETSIZE:
                if (!arg) return -EINVAL;
                err = verify_area(VERIFY_WRITE,(long *) arg,sizeof(long));
                if (err) return (err);
                put_user(pd_hd[dev].nr_sects,(long *) arg);
                return (0);
            case BLKRRPART:
		if (!capable(CAP_SYS_ADMIN))
			return -EACCES;
                return pd_revalidate(inode->i_rdev);
	    case BLKROSET:
	    case BLKROGET:
	    case BLKRASET:
	    case BLKRAGET:
	    case BLKFLSBUF:
	    case BLKPG:
		return blk_ioctl(inode->i_rdev, cmd, arg);
            default:
                return -EINVAL;
        }
}

static int pd_release (struct inode *inode, struct file *file)

{       kdev_t devp;
	int	unit;

        devp = inode->i_rdev;
	unit = DEVICE_NR(devp);

	if ((unit >= PD_UNITS) || (PD.access <= 0)) 
		return -EINVAL;

	PD.access--;

        if (!PD.access && PD.removable)
		pd_doorlock(unit,IDE_DOORUNLOCK);

        MOD_DEC_USE_COUNT;

	return 0;
}

static int pd_check_media( kdev_t dev)

{       int r, unit;

	unit = DEVICE_NR(dev);
	if ((unit >= PD_UNITS) || (!PD.present)) return -ENODEV;
        if (!PD.removable) return 0;
	pd_media_check(unit);
	r = PD.changed;
	PD.changed = 0;
	return r;
}

static int pd_revalidate(kdev_t dev)

{       int p, unit, minor;
        long flags;
        kdev_t devp;

	struct super_block *sb;

        unit = DEVICE_NR(dev);
        if ((unit >= PD_UNITS) || (!PD.present)) return -ENODEV;

        save_flags(flags);
        cli(); 
        if (PD.access > 1) {
                restore_flags(flags);
                return -EBUSY;
        }
        pd_valid = 0;
        restore_flags(flags);   

        for (p=(PD_PARTNS-1);p>=0;p--) {
		minor = p + unit*PD_PARTNS;
                devp = MKDEV(MAJOR_NR, minor);
                fsync_dev(devp);

                sb = get_super(devp);
                if (sb) invalidate_inodes(sb);

                invalidate_buffers(devp);
                pd_hd[minor].start_sect = 0;
                pd_hd[minor].nr_sects = 0;
        }

	if (pd_identify(unit))
		grok_partitions(&pd_gendisk,unit,1<<PD_BITS,PD.capacity);

        pd_valid = 1;
        wake_up(&pd_wait_open);

        return 0;
}

#ifdef MODULE

/* Glue for modules ... */

void    cleanup_module(void);

int     init_module(void)

{

#ifdef PARIDE_JUMBO
       { extern paride_init();
         paride_init();
       } 
#endif
        return pd_init();
}

void    cleanup_module(void)

{       struct gendisk **gdp;
	int unit;

        devfs_unregister_blkdev(MAJOR_NR,name);
        for(gdp=&gendisk_head;*gdp;gdp=&((*gdp)->next))
                if (*gdp == &pd_gendisk) break;
        if (*gdp) *gdp = (*gdp)->next;

	for (unit=0;unit<PD_UNITS;unit++) 
	   if (PD.present) pi_release(PI);
}

#endif

#define	WR(c,r,v)	pi_write_regr(PI,c,r,v)
#define	RR(c,r)		(pi_read_regr(PI,c,r))

#define DRIVE		(0xa0+0x10*PD.drive)

/*  ide command interface */

static void pd_print_error( int unit, char * msg, int status )

{       int     i;

	printk("%s: %s: status = 0x%x =",PD.name,msg,status);
        for(i=0;i<18;i++) if (status & (1<<i)) printk(" %s",pd_errs[i]);
	printk("\n");
}

static void pd_reset( int unit )    /* called only for MASTER drive */

{       pi_connect(PI);
	WR(1,6,4);
        udelay(50);
        WR(1,6,0);
	pi_disconnect(PI);
	udelay(250);
}

#define DBMSG(msg)	((verbose>1)?(msg):NULL)

static int pd_wait_for( int unit, int w, char * msg )    /* polled wait */

{       int     k, r, e;

        k=0;
        while(k < PD_SPIN) { 
            r = RR(1,6);
            k++;
            if (((r & w) == w) && !(r & STAT_BUSY)) break;
            udelay(PD_SPIN_DEL);
        }
        e = (RR(0,1)<<8) + RR(0,7);
        if (k >= PD_SPIN)  e |= ERR_TMO;
        if ((e & (STAT_ERR|ERR_TMO)) && (msg != NULL)) 
		pd_print_error(unit,msg,e);
        return e;
}

static void pd_send_command( int unit, int n, int s, int h, 
			     int c0, int c1, int func )

{
        WR(0,6,DRIVE+h);
        WR(0,1,0);                /* the IDE task file */
        WR(0,2,n);
        WR(0,3,s);
        WR(0,4,c0);
        WR(0,5,c1);
        WR(0,7,func);

        udelay(1);
}

static void pd_ide_command( int unit, int func, int block, int count )

/* Don't use this call if the capacity is zero. */

{       int c1, c0, h, s;

        s  = ( block % PD.sectors) + 1;
        h  = ( block / PD.sectors) % PD.heads;
        c0 = ( block / (PD.sectors*PD.heads)) % 256;
        c1 = ( block / (PD.sectors*PD.heads*256));

        pd_send_command(unit,count,s,h,c0,c1,func);
}

/* According to the ATA standard, the default CHS geometry should be
   available following a reset.  Some Western Digital drives come up
   in a mode where only LBA addresses are accepted until the device
   parameters are initialised.
*/

static void pd_init_dev_parms( int unit )
 
{       pi_connect(PI);
        pd_wait_for(unit,0,DBMSG("before init_dev_parms"));
        pd_send_command(unit,PD.sectors,0,PD.heads-1,0,0,IDE_INIT_DEV_PARMS);
        udelay(300);
        pd_wait_for(unit,0,"Initialise device parameters");
        pi_disconnect(PI);
}