[PATCH 2/3] scsi: add expect_media_change_suspend sysfs device setting

[Martin Kepplinger]

Add a user-facing flag that sets expecting_media_change on runtime
resume. That works around devices that send MEDIA_CHANGED when it
actually is just resumed from suspend and the media can be expected
not to have changed.

Signed-off-by: Martin Kepplinger <martin.kepplinger@xxxxxxx>
---
 drivers/scsi/scsi_sysfs.c  | 38 ++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_device.h |  2 ++
 2 files changed, 40 insertions(+)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index b6378c8ca783..a049290addff 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1189,6 +1189,43 @@ static DEVICE_ATTR(queue_ramp_up_period, S_IRUGO | S_IWUSR,
 		   sdev_show_queue_ramp_up_period,
 		   sdev_store_queue_ramp_up_period);
 
+static ssize_t
+sdev_show_expect_media_change_suspend(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct scsi_device *sdev;
+	sdev = to_scsi_device(dev);
+
+	if (sdev->expect_media_change_suspend)
+		return sprintf(buf, "1\n");
+	else
+		return sprintf(buf, "0\n");
+}
+
+static ssize_t
+sdev_store_expect_media_change_suspend(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t count)
+{
+	struct scsi_device *sdev;
+	unsigned int flag;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	sdev = to_scsi_device(dev);
+	err = kstrtouint(buf, 10, &flag);
+	if (err)
+		return err;
+	sdev->expect_media_change_suspend = !!flag;
+
+	return count;
+}
+static DEVICE_ATTR(expect_media_change_suspend, S_IRUGO | S_IWUSR,
+		   sdev_show_expect_media_change_suspend,
+		   sdev_store_expect_media_change_suspend);
+
 static umode_t scsi_sdev_attr_is_visible(struct kobject *kobj,
 					 struct attribute *attr, int i)
 {
@@ -1260,6 +1297,7 @@ static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_queue_type.attr,
 	&dev_attr_wwid.attr,
 	&dev_attr_blacklist.attr,
+	&dev_attr_expect_media_change_suspend.attr,
 #ifdef CONFIG_SCSI_DH
 	&dev_attr_dh_state.attr,
 	&dev_attr_access_state.attr,
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index ca2c3eb5830f..fafb8e6ea4d0 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -171,6 +171,8 @@ struct scsi_device {
 	unsigned expecting_cc_ua:1; /* Expecting a CHECK_CONDITION/UNIT_ATTN
 				     * because we did a bus reset. */
 	unsigned expecting_media_change:1; /* Expecting "media changed" UA */
+	unsigned expect_media_change_suspend:1; /* User facing flag to enable
+						 * the above flag on runtime resume */
 	unsigned use_10_for_rw:1; /* first try 10-byte read / write */
 	unsigned use_10_for_ms:1; /* first try 10-byte mode sense/select */
 	unsigned set_dbd_for_ms:1; /* Set "DBD" field in mode sense */
-- 
2.20.1