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Subject[PATCH 1/4] block: add function disk_name_format() into block core
  According to 3e1a7ff8a0a7b948f2684930166954f9e8e776fe,
I copied function "sd_format_disk_name()" into block core with
the name of "disk_name_format()".

Signed-off-by: Ren Mingxin <renmx@cn.fujitsu.com>
---
block/genhd.c | 49
+++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/genhd.h | 2 ++
2 files changed, 51 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index df9816e..10c04b6 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -357,6 +357,55 @@ void unregister_blkdev(unsigned int major, const
char *name)

EXPORT_SYMBOL(unregister_blkdev);

+/*
+ * disk_name_format - format disk name
+ * @prefix: name prefix - ie. "sd" for SCSI disks
+ * @index: index of the disk to format name for
+ * @buf: output buffer
+ * @buflen: length of the output buffer
+ *
+ * Take SCSI disks for example. Disk names starts at sda. The
+ * 26th device is sdz and the 27th is sdaa. The last one for
+ * two lettered suffix is sdzz which is followed by sdaaa.
+ *
+ * This is basically 26 base counting with one extra 'nil' entry
+ * at the beginning from the second digit on and can be
+ * determined using similar method as 26 base conversion with the
+ * index shifted -1 after each digit is computed.
+ *
+ * CONTEXT:
+ * Don't care.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+
+int disk_name_format(char *prefix, int index, char *buf, int buflen)
+{
+ const int base = 'z' - 'a' + 1;
+ char *begin = buf + strlen(prefix);
+ char *end = buf + buflen;
+ char *p;
+ int unit;
+
+ p = end - 1;
+ *p = '\0';
+ unit = base;
+ do {
+ if (p == begin)
+ return -EINVAL;
+ *--p = 'a' + (index % unit);
+ index = (index / unit) - 1;
+ } while (index >= 0);
+
+ memmove(begin, p, end - p);
+ memcpy(buf, prefix, strlen(prefix));
+
+ return 0;
+}
+
+EXPORT_SYMBOL(disk_name_format);
+
static struct kobj_map *bdev_map;

/**
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index e61d319..cd3d5e5 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -407,6 +407,8 @@ static inline void free_part_info(struct hd_struct
*part)
extern void part_round_stats(int cpu, struct hd_struct *part);

/* block/genhd.c */
+extern int disk_name_format(char *prefix, int index, char *buf, int
buflen);
+
extern void add_disk(struct gendisk *disk);
extern void del_gendisk(struct gendisk *gp);
extern struct gendisk *get_gendisk(dev_t dev, int *partno);


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