+/**
+ * sd_format_disk_name - 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
+ *
+ * SCSI 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 beggining 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.
+ */
+static int sd_format_disk_name(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;
+}
+