[SCSI] st: show options currently set in sysfs

Show the current binary tape driver and mode options is sysfs. A file
(options) is created in each directory in /sys/class/scsi_tape. The files
contain masks showing the options. The mask bit definitions are the same as
used when setting the options using the MTSETDRVBUFFER function in the
MTIOCTOP ioctl (defined in include/linux/mtio.h). For example:
> cat /sys/class/scsi_tape/nst0/options
0x00000d07

[jejb: updated doc with correction from Randy Dunlap]

Signed-off-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index a4361a8c6ac6..d204aad2e683 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -4365,6 +4365,46 @@ static ssize_t st_defcompression_show(struct class_device *class_dev, char *buf)
 
 CLASS_DEVICE_ATTR(default_compression, S_IRUGO, st_defcompression_show, NULL);
 
+static ssize_t st_options_show(struct class_device *class_dev, char *buf)
+{
+        struct st_modedef *STm = (struct st_modedef *)class_get_devdata(class_dev);
+        struct scsi_tape *STp;
+        int i, j, options;
+        ssize_t l = 0;
+
+        for (i=0; i < st_dev_max; i++) {
+                for (j=0; j < ST_NBR_MODES; j++)
+                        if (&scsi_tapes[i]->modes[j] == STm)
+                                break;
+                if (j < ST_NBR_MODES)
+                        break;
+        }
+        if (i == st_dev_max)
+                return 0;  /* should never happen */
+
+        STp = scsi_tapes[i];
+
+        options = STm->do_buffer_writes ? MT_ST_BUFFER_WRITES : 0;
+        options |= STm->do_async_writes ? MT_ST_ASYNC_WRITES : 0;
+        options |= STm->do_read_ahead ? MT_ST_READ_AHEAD : 0;
+        DEB( options |= debugging ? MT_ST_DEBUGGING : 0 );
+        options |= STp->two_fm ? MT_ST_TWO_FM : 0;
+        options |= STp->fast_mteom ? MT_ST_FAST_MTEOM : 0;
+        options |= STm->defaults_for_writes ? MT_ST_DEF_WRITES : 0;
+        options |= STp->can_bsr ? MT_ST_CAN_BSR : 0;
+        options |= STp->omit_blklims ? MT_ST_NO_BLKLIMS : 0;
+        options |= STp->can_partitions ? MT_ST_CAN_PARTITIONS : 0;
+        options |= STp->scsi2_logical ? MT_ST_SCSI2LOGICAL : 0;
+        options |= STm->sysv ? MT_ST_SYSV : 0;
+        options |= STp->immediate ? MT_ST_NOWAIT : 0;
+        options |= STp->sili ? MT_ST_SILI : 0;
+
+        l = snprintf(buf, PAGE_SIZE, "0x%08x\n", options);
+        return l;
+}
+
+CLASS_DEVICE_ATTR(options, S_IRUGO, st_options_show, NULL);
+
 static int do_create_class_files(struct scsi_tape *STp, int dev_num, int mode)
 {
         int i, rew, error;
@@ -4402,6 +4442,9 @@ static int do_create_class_files(struct scsi_tape *STp, int dev_num, int mode)
                 error = class_device_create_file(st_class_member,
                                         &class_device_attr_default_compression);
                 if (error) goto out;
+                error = class_device_create_file(st_class_member,
+                                        &class_device_attr_options);
+                if (error) goto out;
 
                 if (mode == 0 && rew == 0) {
                         error = sysfs_create_link(&STp->device->sdev_gendev.kobj,