sd.c

讲述linux的初始化过程

			int hard_sector = sector_size;
			int sz = rscsi_disks[i].capacity * (hard_sector/256);

			/* There are 16 minors allocated for each major device */
			for (m = i << 4; m < ((i + 1) << 4); m++) {
				sd_hardsizes[m] = hard_sector;
			}

			printk("SCSI device %s: "
			       "%d %d-byte hdwr sectors (%d MB)\n",
			       nbuff, rscsi_disks[i].capacity,
			       hard_sector, (sz/2 - sz/1250 + 974)/1950);
		}

		/* Rescale capacity to 512-byte units */
		if (sector_size == 4096)
			rscsi_disks[i].capacity <<= 3;
		if (sector_size == 2048)
			rscsi_disks[i].capacity <<= 2;
		if (sector_size == 1024)
			rscsi_disks[i].capacity <<= 1;
		if (sector_size == 256)
			rscsi_disks[i].capacity >>= 1;
	}


	/*
	 * Unless otherwise specified, this is not write protected.
	 */
	rscsi_disks[i].write_prot = 0;
	if (rscsi_disks[i].device->removable && rscsi_disks[i].ready) {
		/* FLOPTICAL */

		/*
		 * For removable scsi disk ( FLOPTICAL ) we have to recognise
		 * the Write Protect Flag. This flag is kept in the Scsi_Disk
		 * struct and tested at open !
		 * Daniel Roche ( [e-mail] )
		 *
		 * Changed to get all pages (0x3f) rather than page 1 to
		 * get around devices which do not have a page 1.  Since
		 * we're only interested in the header anyway, this should
		 * be fine.
		 *   -- Matthew Dharm ([e-mail])
		 */

		memset((void *) &cmd[0], 0, 8);
		cmd[0] = MODE_SENSE;
		cmd[1] = (rscsi_disks[i].device->lun << 5) & 0xe0;
		cmd[2] = 0x3f;	/* Get all pages */
		cmd[4] = 8;     /* But we only want the 8 byte header */
		SRpnt->sr_cmd_len = 0;
		SRpnt->sr_sense_buffer[0] = 0;
		SRpnt->sr_sense_buffer[2] = 0;

		/* same code as READCAPA !! */
		SRpnt->sr_data_direction = SCSI_DATA_READ;
		scsi_wait_req(SRpnt, (void *) cmd, (void *) buffer,
			    512, SD_TIMEOUT, MAX_RETRIES);

		the_result = SRpnt->sr_result;

		if (the_result) {
			printk("%s: test WP failed, assume Write Protected\n", nbuff);
			rscsi_disks[i].write_prot = 1;
		} else {
			rscsi_disks[i].write_prot = ((buffer[2] & 0x80) != 0);
			printk("%s: Write Protect is %s\n", nbuff,
			       rscsi_disks[i].write_prot ? "on" : "off");
		}

	}			/* check for write protect */
	SRpnt->sr_device->ten = 1;
	SRpnt->sr_device->remap = 1;
	SRpnt->sr_device->sector_size = sector_size;
	/* Wake up a process waiting for device */
	scsi_release_request(SRpnt);
	SRpnt = NULL;

	scsi_free(buffer, 512);
	return i;
}

/*
 * The sd_init() function looks at all SCSI drives present, determines
 * their size, and reads partition table entries for them.
 */

static int sd_registered;

static int sd_init()
{
	int i;

	if (sd_template.dev_noticed == 0)
		return 0;

	if (!rscsi_disks)
		sd_template.dev_max = sd_template.dev_noticed + SD_EXTRA_DEVS;

	if (sd_template.dev_max > N_SD_MAJORS * SCSI_DISKS_PER_MAJOR)
		sd_template.dev_max = N_SD_MAJORS * SCSI_DISKS_PER_MAJOR;

	if (!sd_registered) {
		for (i = 0; i < N_USED_SD_MAJORS; i++) {
			if (devfs_register_blkdev(SD_MAJOR(i), "sd", &sd_fops)) {
				printk("Unable to get major %d for SCSI disk\n", SD_MAJOR(i));
				return 1;
			}
		}
		sd_registered++;
	}
	/* We do not support attaching loadable devices yet. */
	if (rscsi_disks)
		return 0;

	rscsi_disks = kmalloc(sd_template.dev_max * sizeof(Scsi_Disk), GFP_ATOMIC);
	if (!rscsi_disks)
		goto cleanup_devfs;
	memset(rscsi_disks, 0, sd_template.dev_max * sizeof(Scsi_Disk));

	/* for every (necessary) major: */
	sd_sizes = kmalloc((sd_template.dev_max << 4) * sizeof(int), GFP_ATOMIC);
	if (!sd_sizes)
		goto cleanup_disks;
	memset(sd_sizes, 0, (sd_template.dev_max << 4) * sizeof(int));

	sd_blocksizes = kmalloc((sd_template.dev_max << 4) * sizeof(int), GFP_ATOMIC);
	if (!sd_blocksizes)
		goto cleanup_sizes;
	
	sd_hardsizes = kmalloc((sd_template.dev_max << 4) * sizeof(int), GFP_ATOMIC);
	if (!sd_hardsizes)
		goto cleanup_blocksizes;

	for (i = 0; i < sd_template.dev_max << 4; i++) {
		sd_blocksizes[i] = 1024;
		sd_hardsizes[i] = 512;
	}

	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		blksize_size[SD_MAJOR(i)] = sd_blocksizes + i * (SCSI_DISKS_PER_MAJOR << 4);
		hardsect_size[SD_MAJOR(i)] = sd_hardsizes + i * (SCSI_DISKS_PER_MAJOR << 4);
	}
	sd = kmalloc((sd_template.dev_max << 4) *
					  sizeof(struct hd_struct),
					  GFP_ATOMIC);
	if (!sd)
		goto cleanup_sd;
	memset(sd, 0, (sd_template.dev_max << 4) * sizeof(struct hd_struct));

	if (N_USED_SD_MAJORS > 1)
		sd_gendisks = kmalloc(N_USED_SD_MAJORS * sizeof(struct gendisk), GFP_ATOMIC);
		if (!sd_gendisks)
			goto cleanup_sd_gendisks;
	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		sd_gendisks[i] = sd_gendisk;
		sd_gendisks[i].de_arr = kmalloc (SCSI_DISKS_PER_MAJOR * sizeof *sd_gendisks[i].de_arr,
                                                 GFP_ATOMIC);
		if (!sd_gendisks[i].de_arr)
			goto cleanup_gendisks_de_arr;
                memset (sd_gendisks[i].de_arr, 0,
                        SCSI_DISKS_PER_MAJOR * sizeof *sd_gendisks[i].de_arr);
		sd_gendisks[i].flags = kmalloc (SCSI_DISKS_PER_MAJOR * sizeof *sd_gendisks[i].flags,
                                                GFP_ATOMIC);
		if (!sd_gendisks[i].flags)
			goto cleanup_gendisks_flags;
                memset (sd_gendisks[i].flags, 0,
                        SCSI_DISKS_PER_MAJOR * sizeof *sd_gendisks[i].flags);
		sd_gendisks[i].major = SD_MAJOR(i);
		sd_gendisks[i].major_name = "sd";
		sd_gendisks[i].minor_shift = 4;
		sd_gendisks[i].max_p = 1 << 4;
		sd_gendisks[i].part = sd + (i * SCSI_DISKS_PER_MAJOR << 4);
		sd_gendisks[i].sizes = sd_sizes + (i * SCSI_DISKS_PER_MAJOR << 4);
		sd_gendisks[i].nr_real = 0;
		sd_gendisks[i].next = sd_gendisks + i + 1;
		sd_gendisks[i].real_devices =
		    (void *) (rscsi_disks + i * SCSI_DISKS_PER_MAJOR);
	}

	LAST_SD_GENDISK.next = NULL;
	return 0;

cleanup_gendisks_flags:
	kfree(sd_gendisks[i].de_arr);
cleanup_gendisks_de_arr:
	while (--i >= 0 ) {
		kfree(sd_gendisks[i].de_arr);
		kfree(sd_gendisks[i].flags);
	}
	kfree(sd_gendisks);
cleanup_sd_gendisks:
	kfree(sd);
cleanup_sd:
	kfree(sd_hardsizes);
cleanup_blocksizes:
	kfree(sd_blocksizes);
cleanup_sizes:
	kfree(sd_sizes);
cleanup_disks:
	kfree(rscsi_disks);
cleanup_devfs:
	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		devfs_unregister_blkdev(SD_MAJOR(i), "sd");
	}
	sd_registered--;
	return 1;
}


static void sd_finish()
{
	struct gendisk *gendisk;
	int i;

	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		blk_dev[SD_MAJOR(i)].queue = sd_find_queue;
	}
	for (gendisk = gendisk_head; gendisk != NULL; gendisk = gendisk->next)
		if (gendisk == sd_gendisks)
			break;
	if (gendisk == NULL) {
		LAST_SD_GENDISK.next = gendisk_head;
		gendisk_head = sd_gendisks;
	}
	for (i = 0; i < sd_template.dev_max; ++i)
		if (!rscsi_disks[i].capacity && rscsi_disks[i].device) {
			sd_init_onedisk(i);
			if (!rscsi_disks[i].has_part_table) {
				sd_sizes[i << 4] = rscsi_disks[i].capacity;
				register_disk(&SD_GENDISK(i), MKDEV_SD(i),
						1<<4, &sd_fops,
						rscsi_disks[i].capacity);
				rscsi_disks[i].has_part_table = 1;
			}
		}
	/* If our host adapter is capable of scatter-gather, then we increase
	 * the read-ahead to 60 blocks (120 sectors).  If not, we use
	 * a two block (4 sector) read ahead. We can only respect this with the
	 * granularity of every 16 disks (one device major).
	 */
	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		read_ahead[SD_MAJOR(i)] =
		    (rscsi_disks[i * SCSI_DISKS_PER_MAJOR].device
		     && rscsi_disks[i * SCSI_DISKS_PER_MAJOR].device->host->sg_tablesize)
		    ? 120	/* 120 sector read-ahead */
		    : 4;	/* 4 sector read-ahead */
	}

	return;
}

static int sd_detect(Scsi_Device * SDp)
{
	char nbuff[6];
	if (SDp->type != TYPE_DISK && SDp->type != TYPE_MOD)
		return 0;

	sd_devname(sd_template.dev_noticed++, nbuff);
	printk("Detected scsi %sdisk %s at scsi%d, channel %d, id %d, lun %d\n",
	       SDp->removable ? "removable " : "",
	       nbuff,
	       SDp->host->host_no, SDp->channel, SDp->id, SDp->lun);

	return 1;
}

static int sd_attach(Scsi_Device * SDp)
{
        unsigned int devnum;
	Scsi_Disk *dpnt;
	int i;

	if (SDp->type != TYPE_DISK && SDp->type != TYPE_MOD)
		return 0;

	if (sd_template.nr_dev >= sd_template.dev_max) {
		SDp->attached--;
		return 1;
	}
	for (dpnt = rscsi_disks, i = 0; i < sd_template.dev_max; i++, dpnt++)
		if (!dpnt->device)
			break;

	if (i >= sd_template.dev_max)
		panic("scsi_devices corrupt (sd)");

	rscsi_disks[i].device = SDp;
	rscsi_disks[i].has_part_table = 0;
	sd_template.nr_dev++;
	SD_GENDISK(i).nr_real++;
        devnum = i % SCSI_DISKS_PER_MAJOR;
        SD_GENDISK(i).de_arr[devnum] = SDp->de;
        if (SDp->removable)
		SD_GENDISK(i).flags[devnum] |= GENHD_FL_REMOVABLE;
	return 0;
}

#define DEVICE_BUSY rscsi_disks[target].device->busy
#define USAGE rscsi_disks[target].device->access_count
#define CAPACITY rscsi_disks[target].capacity
#define MAYBE_REINIT  sd_init_onedisk(target)

/* This routine is called to flush all partitions and partition tables
 * for a changed scsi disk, and then re-read the new partition table.
 * If we are revalidating a disk because of a media change, then we
 * enter with usage == 0.  If we are using an ioctl, we automatically have
 * usage == 1 (we need an open channel to use an ioctl :-), so this
 * is our limit.
 */
int revalidate_scsidisk(kdev_t dev, int maxusage)
{
	int target;
	int max_p;
	int start;
	int i;

	target = DEVICE_NR(dev);

	if (DEVICE_BUSY || USAGE > maxusage) {
		printk("Device busy for revalidation (usage=%d)\n", USAGE);
		return -EBUSY;
	}
	DEVICE_BUSY = 1;

	max_p = sd_gendisks->max_p;
	start = target << sd_gendisks->minor_shift;

	for (i = max_p - 1; i >= 0; i--) {
		int index = start + i;
		kdev_t devi = MKDEV_SD_PARTITION(index);
		struct super_block *sb = get_super(devi);
		sync_dev(devi);
		if (sb)
			invalidate_inodes(sb);
		invalidate_buffers(devi);
		sd_gendisks->part[index].start_sect = 0;
		sd_gendisks->part[index].nr_sects = 0;
		/*
		 * Reset the blocksize for everything so that we can read
		 * the partition table.  Technically we will determine the
		 * correct block size when we revalidate, but we do this just
		 * to make sure that everything remains consistent.
		 */
		sd_blocksizes[index] = 1024;
		if (rscsi_disks[target].device->sector_size == 2048)
			sd_blocksizes[index] = 2048;
		else
			sd_blocksizes[index] = 1024;
	}

#ifdef MAYBE_REINIT
	MAYBE_REINIT;
#endif

	grok_partitions(&SD_GENDISK(target), target % SCSI_DISKS_PER_MAJOR,
			1<<4, CAPACITY);

	DEVICE_BUSY = 0;
	return 0;
}

static int fop_revalidate_scsidisk(kdev_t dev)
{
	return revalidate_scsidisk(dev, 0);
}
static void sd_detach(Scsi_Device * SDp)
{
	Scsi_Disk *dpnt;
	int i, j;
	int max_p;
	int start;

	for (dpnt = rscsi_disks, i = 0; i < sd_template.dev_max; i++, dpnt++)
		if (dpnt->device == SDp) {

			/* If we are disconnecting a disk driver, sync and invalidate
			 * everything */
			max_p = sd_gendisk.max_p;
			start = i << sd_gendisk.minor_shift;

			for (j = max_p - 1; j >= 0; j--) {
				int index = start + j;
				kdev_t devi = MKDEV_SD_PARTITION(index);
				struct super_block *sb = get_super(devi);
				sync_dev(devi);
				if (sb)
					invalidate_inodes(sb);
				invalidate_buffers(devi);
				sd_gendisks->part[index].start_sect = 0;
				sd_gendisks->part[index].nr_sects = 0;
				sd_sizes[index] = 0;
			}
                        devfs_register_partitions (&SD_GENDISK (i),
                                                   SD_MINOR_NUMBER (start), 1);
			/* unregister_disk() */
			dpnt->has_part_table = 0;
			dpnt->device = NULL;
			dpnt->capacity = 0;
			SDp->attached--;
			sd_template.dev_noticed--;
			sd_template.nr_dev--;
			SD_GENDISK(i).nr_real--;
			return;
		}
	return;
}

static int __init init_sd(void)
{
	sd_template.module = THIS_MODULE;
	return scsi_register_module(MODULE_SCSI_DEV, &sd_template);
}

static void __exit exit_sd(void)
{
	struct gendisk **prev_sdgd_link;
	struct gendisk *sdgd;
	int i;
	int removed = 0;

	scsi_unregister_module(MODULE_SCSI_DEV, &sd_template);

	for (i = 0; i < N_USED_SD_MAJORS; i++)
		devfs_unregister_blkdev(SD_MAJOR(i), "sd");

	sd_registered--;
	if (rscsi_disks != NULL) {
		kfree(rscsi_disks);
		kfree(sd_sizes);
		kfree(sd_blocksizes);
		kfree(sd_hardsizes);
		kfree((char *) sd);

		/*
		 * Now remove sd_gendisks from the linked list
		 */
		prev_sdgd_link = &gendisk_head;
		while ((sdgd = *prev_sdgd_link) != NULL) {
			if (sdgd >= sd_gendisks && sdgd <= &LAST_SD_GENDISK) {
				removed++;
				*prev_sdgd_link = sdgd->next;
				continue;
			}
			prev_sdgd_link = &sdgd->next;
		}

		if (removed != N_USED_SD_MAJORS)
			printk("%s %d sd_gendisks in disk chain",
			       removed > N_USED_SD_MAJORS ? "total" : "just", removed);

	}
	for (i = 0; i < N_USED_SD_MAJORS; i++) {
		blk_size[SD_MAJOR(i)] = NULL;
		hardsect_size[SD_MAJOR(i)] = NULL;
		read_ahead[SD_MAJOR(i)] = 0;
	}
	sd_template.dev_max = 0;
	if (sd_gendisks != &sd_gendisk)
		kfree(sd_gendisks);
}

module_init(init_sd);
module_exit(exit_sd);