If the value read from the file is 1, reads and writes from/to the
device are blocked because the tape position may not match user's
expectation (tape rewound after device reset).
Signed-off-by: Kai Mäkisara <Kai.Makisara@xxxxxxxxxxx>
---
Documentation/scsi/st.rst | 5 +++++
drivers/scsi/st.c | 19 +++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/Documentation/scsi/st.rst b/Documentation/scsi/st.rst
index d3b28c28d74c..2209f03faad3 100644
--- a/Documentation/scsi/st.rst
+++ b/Documentation/scsi/st.rst
@@ -157,6 +157,11 @@ enabled driver and mode options. The value in the file is a bit mask where the
bit definitions are the same as those used with MTSETDRVBUFFER in setting the
options.
+Each directory contains the entry 'reset_blocked'. If this value is one,
+reading and writing to the device is blocked after device reset. Most
+devices rewind the tape after reset and the writes/read don't access the
+tape position the user expects.
+
A link named 'tape' is made from the SCSI device directory to the class
directory corresponding to the mode 0 auto-rewind device (e.g., st0).
diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index ad86dfbc8919..0e6a87f1f47f 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -4697,6 +4697,24 @@ options_show(struct device *dev, struct device_attribute *attr, char *buf)
}
static DEVICE_ATTR_RO(options);
+/**
+ * reset_blocked_show - Value 1 indicates that reads, writes, etc. are blocked
+ * because a device reset has occurred and no operation positioning the tape
+ * has been issued.
+ * @dev: struct device
+ * @attr: attribute structure
+ * @buf: buffer to return formatted data in
+ */
+static ssize_t reset_blocked_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct st_modedef *STm = dev_get_drvdata(dev);
+ struct scsi_tape *STp = STm->tape;
+
+ return sprintf(buf, "%d", STp->pos_unknown);
+}
+static DEVICE_ATTR_RO(reset_blocked);
+
/* Support for tape stats */
/**
@@ -4881,6 +4899,7 @@ static struct attribute *st_dev_attrs[] = {
&dev_attr_default_density.attr,
&dev_attr_default_compression.attr,
&dev_attr_options.attr,
+ &dev_attr_reset_blocked.attr,
NULL,
};
--
2.43.0
