[PATCH] Add char_devs to st

This patch adds support for cdevs to the st driver. The changes are based on
Doug Gilbert's corresponding changes to the sg driver. Using cdevs brings the
following advantanges:
- support for many drives, currently the maximum is set to 128; the minor
  number assignment is explained in the patch to Documentation/scsi/README.st
- the tape devices appear in /sys/cdev/major/st*, as an example here are
  the entries for the first drive (4 modes, rewind and non-rewind
  devices):
  /sys/cdev/major/st0m0   /sys/cdev/major/st0m1   /sys/cdev/major/st0m2
  /sys/cdev/major/st0m3
  /sys/cdev/major/st0m0n  /sys/cdev/major/st0m1n  /sys/cdev/major/st0m2n
  /sys/cdev/major/st0m3n

Documentation/scsi/st.txt

@@ -2,7 +2,7 @@ This file contains brief information about the SCSI tape driver.
 The driver is currently maintained by Kai Mäkisara (email
 Kai.Makisara@kolumbus.fi)
 
-Last modified: Sat Apr 12 20:26:37 2003 by makisara
+Last modified: Sun Nov  9 22:36:02 2003 by makisara
 
 
 BASICS
@@ -95,6 +95,24 @@ tape in the drive (commands trying to write something return error if
 attempted).
 
 
+MINOR NUMBERS
+
+The tape driver currently supports 128 drives by default. This number
+can be increased by editing st.h and recompiling the driver if
+necessary. The upper limit is 2^17 drives if 4 modes for each drive
+are used.
+
+The minor numbers consist of the following bit fields:
+
+dev_upper non-rew mode dev-lower
+  20 -  8     7    6 5  4      0
+The non-rewind bit is always bit 7 (the uppermost bit in the lowermost
+byte). The bits defining the mode are next to the non-rewind bits. The
+remaining bits define the tape device number. This numbering is
+backward compatible with the numbering used when the minor number was
+only 8 bits wide.
+
+
 BSD AND SYS V SEMANTICS
 
 The user can choose between these two behaviours of the tape driver by

drivers/scsi/st.c

@@ -17,7 +17,7 @@
    Last modified: 18-JAN-1998 Richard Gooch <rgooch@atnf.csiro.au> Devfs support
  */
 
-static char *verstr = "20030811";
+static char *verstr = "20031228";
 
 #include <linux/module.h>
 
@@ -35,6 +35,7 @@ static char *verstr = "20030811";
 #include <linux/blkdev.h>
 #include <linux/moduleparam.h>
 #include <linux/devfs_fs_kernel.h>
+#include <linux/cdev.h>
 #include <asm/uaccess.h>
 #include <asm/dma.h>
 #include <asm/system.h>
@@ -140,14 +141,19 @@ DEB( static int debugging = DEBUG; )
 #define ST_TIMEOUT (900 * HZ)
 #define ST_LONG_TIMEOUT (14000 * HZ)
 
-#define TAPE_NR(x) (iminor(x) & ~(-1 << ST_MODE_SHIFT))
+/* Remove mode bits and auto-rewind bit (7) */
+#define TAPE_NR(x) ( ((iminor(x) & ~255) >> (ST_NBR_MODE_BITS + 1)) | \
+    (iminor(x) & ~(-1 << ST_MODE_SHIFT)) )
 #define TAPE_MODE(x) ((iminor(x) & ST_MODE_MASK) >> ST_MODE_SHIFT)
 
+/* Construct the minor number from the device (d), mode (m), and non-rewind (n) data */
+#define TAPE_MINOR(d, m, n) (((d & ~(255 >> (ST_NBR_MODE_BITS + 1))) << (ST_NBR_MODE_BITS + 1)) | \
+  (d & (255 >> (ST_NBR_MODE_BITS + 1))) | (m << ST_MODE_SHIFT) | ((n != 0) << 7) )
+
 /* Internal ioctl to set both density (uppermost 8 bits) and blocksize (lower
    24 bits) */
 #define SET_DENS_AND_BLK 0x10001
 
-#define ST_DEV_ARR_LUMP  6
 static rwlock_t st_dev_arr_lock = RW_LOCK_UNLOCKED;
 
 static int st_fixed_buffer_size = ST_FIXED_BUFFER_SIZE;
@@ -1006,7 +1012,6 @@ static int st_open(struct inode *inode, struct file *filp)
 	write_unlock(&st_dev_arr_lock);
 	STp->rew_at_close = STp->autorew_dev = (iminor(inode) & 0x80) == 0;
 
-
 	if (!scsi_block_when_processing_errors(STp->device)) {
 		retval = (-ENXIO);
 		goto err_out;
@@ -1970,10 +1975,13 @@ static int st_set_options(Scsi_Tape *STp, long options)
 	long code;
 	ST_mode *STm;
 	char *name = tape_name(STp);
+	struct cdev *cd0, *cd1;
 
 	STm = &(STp->modes[STp->current_mode]);
 	if (!STm->defined) {
+		cd0 = STm->cdevs[0]; cd1 = STm->cdevs[1];
 		memcpy(STm, &(STp->modes[0]), sizeof(ST_mode));
+		STm->cdevs[0] = cd0; STm->cdevs[1] = cd1;
 		modes_defined = TRUE;
                 DEBC(printk(ST_DEB_MSG
                             "%s: Initialized mode %d definition from mode 0\n",
@@ -3704,12 +3712,13 @@ static struct file_operations st_fops =
 static int st_probe(struct device *dev)
 {
 	struct scsi_device *SDp = to_scsi_device(dev);
-	struct gendisk *disk;
-	Scsi_Tape *tpnt;
+	struct gendisk *disk = NULL;
+	struct cdev *cdev = NULL;
+	Scsi_Tape *tpnt = NULL;
 	ST_mode *STm;
 	ST_partstat *STps;
 	ST_buffer *buffer;
-	int i, mode, dev_num;
+	int i, j, mode, dev_num, error;
 	char *stp;
 	u64 bounce_limit;
 
@@ -3743,7 +3752,7 @@ static int st_probe(struct device *dev)
 		Scsi_Tape **tmp_da;
 		int tmp_dev_max;
 
-		tmp_dev_max = st_nr_dev + ST_DEV_ARR_LUMP;
+		tmp_dev_max = max(st_nr_dev * 2, 8);
 		if (tmp_dev_max > ST_MAX_TAPES)
 			tmp_dev_max = ST_MAX_TAPES;
 		if (tmp_dev_max <= st_nr_dev) {
@@ -3837,6 +3846,42 @@ static int st_probe(struct device *dev)
 		STm->default_compression = ST_DONT_TOUCH;
 		STm->default_blksize = (-1);	/* No forced size */
 		STm->default_density = (-1);	/* No forced density */
+
+		for (j=0; j < 2; j++) {
+			cdev = cdev_alloc();
+			if (!cdev) {
+				printk(KERN_ERR
+				       "st: out of memory. Device not attached.\n");
+				goto out_put_disk;
+			}
+			snprintf(cdev->kobj.name, KOBJ_NAME_LEN, "%sm%d%s", disk->disk_name,
+				 i, j ? "n" : "");
+			cdev->owner = THIS_MODULE;
+			cdev->ops = &st_fops;
+			STm->cdevs[j] = cdev;
+
+			error = cdev_add(STm->cdevs[j],
+					 MKDEV(SCSI_TAPE_MAJOR, TAPE_MINOR(dev_num, i, j)),
+					 1);
+			if (error) {
+				printk(KERN_ERR "st%d: Can't add %s-rewind mode %d\n",
+				       dev_num, j ? "non" : "auto", i);
+			}
+
+			error = sysfs_create_link(&STm->cdevs[j]->kobj, &SDp->sdev_gendev.kobj,
+						  "device");
+			if (error) {
+				printk(KERN_ERR
+				       "st%d: Can't create sysfs link from SCSI device.\n",
+				       dev_num);
+			}
+		}
+	}
+	error = sysfs_create_link(&SDp->sdev_gendev.kobj, &tpnt->modes[0].cdevs[0]->kobj,
+				  "tape");
+	if (error) {
+		printk(KERN_ERR "st%d: Can't create sysfs link from SCSI device.\n",
+		       dev_num);
 	}
 
 	for (i = 0; i < ST_NBR_PARTITIONS; i++) {
@@ -3881,17 +3926,28 @@ static int st_probe(struct device *dev)
 
 out_put_disk:
 	put_disk(disk);
+	if (tpnt) {
+		for (i=0; i < ST_NBR_MODES; i++) {
+			STm = &(tpnt->modes[i]);
+			if (STm->cdevs[0])
+				kobject_put(&STm->cdevs[0]->kobj);
+			if (STm->cdevs[1])
+				kobject_put(&STm->cdevs[1]->kobj);
+		}
+		kfree(tpnt);
+	}
 out_buffer_free:
 	kfree(buffer);
 out:
 	return -ENODEV;
 };
 
+
 static int st_remove(struct device *dev)
 {
 	Scsi_Device *SDp = to_scsi_device(dev);
 	Scsi_Tape *tpnt;
-	int i, mode;
+	int i, j, mode;
 
 	write_lock(&st_dev_arr_lock);
 	for (i = 0; i < st_dev_max; i++) {
@@ -3901,9 +3957,16 @@ static int st_remove(struct device *dev)
 			st_nr_dev--;
 			write_unlock(&st_dev_arr_lock);
 			devfs_unregister_tape(tpnt->disk->number);
+			sysfs_remove_link(&SDp->sdev_gendev.kobj, "tape");
 			for (mode = 0; mode < ST_NBR_MODES; ++mode) {
 				devfs_remove("%s/mt%s", SDp->devfs_name, st_formats[mode]);
 				devfs_remove("%s/mt%sn", SDp->devfs_name, st_formats[mode]);
+				for (j=0; j < 2; j++) {
+					sysfs_remove_link(&tpnt->modes[mode].cdevs[j]->kobj,
+							  "device");
+					cdev_del(tpnt->modes[mode].cdevs[j]);
+					tpnt->modes[mode].cdevs[j] = NULL;
+				}
 			}
 			tpnt->device = NULL;
 
@@ -3930,12 +3993,14 @@ static int __init init_st(void)
 		"st: Version %s, fixed bufsize %d, s/g segs %d\n",
 		verstr, st_fixed_buffer_size, st_max_sg_segs);
 
-	if (register_chrdev(SCSI_TAPE_MAJOR, "st", &st_fops) >= 0) {
+	if (!register_chrdev_region(MKDEV(SCSI_TAPE_MAJOR, 0),
+				    ST_MAX_TAPE_ENTRIES, "st")) {
 		if (scsi_register_driver(&st_template.gendrv) == 0) {
 			do_create_driverfs_files();
 			return 0;
 		}
-		unregister_chrdev(SCSI_TAPE_MAJOR, "st");
+		unregister_chrdev_region(MKDEV(SCSI_TAPE_MAJOR, 0),
+					 ST_MAX_TAPE_ENTRIES);
 	}
 
 	printk(KERN_ERR "Unable to get major %d for SCSI tapes\n", SCSI_TAPE_MAJOR);
@@ -3946,7 +4011,8 @@ static void __exit exit_st(void)
 {
 	do_remove_driverfs_files();
 	scsi_unregister_driver(&st_template.gendrv);
-	unregister_chrdev(SCSI_TAPE_MAJOR, "st");
+	unregister_chrdev_region(MKDEV(SCSI_TAPE_MAJOR, 0),
+				 ST_MAX_TAPE_ENTRIES);
 	kfree(scsi_tapes);
 	printk(KERN_INFO "st: Unloaded.\n");
 }

drivers/scsi/st.h

@@ -47,13 +47,16 @@ typedef struct {
 	unsigned char default_compression;	/* 0 = don't touch, etc */
 	short default_density;	/* Forced density, -1 = no value */
 	int default_blksize;	/* Forced blocksize, -1 = no value */
+	struct cdev *cdevs[2];  /* Auto-rewind and non-rewind devices */
 } ST_mode;
 
 #define ST_NBR_MODE_BITS 2
 #define ST_NBR_MODES (1 << ST_NBR_MODE_BITS)
 #define ST_MODE_SHIFT (7 - ST_NBR_MODE_BITS)
 #define ST_MODE_MASK ((ST_NBR_MODES - 1) << ST_MODE_SHIFT)
-#define ST_MAX_TAPES (1 << ST_MODE_SHIFT)
+
+#define ST_MAX_TAPES 128
+#define ST_MAX_TAPE_ENTRIES  (ST_MAX_TAPES << (ST_NBR_MODE_BITS + 1))
 
 /* The status related to each partition */
 typedef struct {