Implement a 'dh_state' sdev attribute for dynamic device handler
manipulation. A read on the attribute will return the name of
the currently attached device handler or 'detached' if no handler
is attached.
The attribute allows the following strings to be written:
- The name of the device handler to be attached if the state is
'detached'.
- 'activate' to trigger path activation if a device handler
is attached.
- 'detach' to detach the currently attached device handler.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
---
drivers/scsi/device_handler/scsi_dh.c | 103 ++++++++++++++++++++++++++++++++-
1 files changed, 102 insertions(+), 1 deletions(-)
Index: linux-2.6.26-git5/drivers/scsi/device_handler/scsi_dh.c
===================================================================
--- linux-2.6.26-git5.orig/drivers/scsi/device_handler/scsi_dh.c
+++ linux-2.6.26-git5/drivers/scsi/device_handler/scsi_dh.c
@@ -84,7 +84,7 @@ static int scsi_dh_handler_attach(struct
* @scsi_dh - Device handler to be detached
*
* Detach from a device handler. If a device handler is specified,
- * only detach if the currently attached handler is equal to it.
+ * only detach if the currently attached handler matches @scsi_dh.
*/
static void scsi_dh_handler_detach(struct scsi_device *sdev,
struct scsi_device_handler *scsi_dh)
@@ -103,6 +103,98 @@ static void scsi_dh_handler_detach(struc
}
/*
+ * Functions for sysfs attribute 'dh_state'
+ */
+static ssize_t
+store_dh_state(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct scsi_device *sdev = to_scsi_device(dev);
+ struct scsi_device_handler *scsi_dh;
+ int err = -EINVAL;
+
+ if (!sdev->scsi_dh_data) {
+ /*
+ * Attach to a device handler
+ */
+ if (!(scsi_dh = get_device_handler(buf)))
+ return err;
+ err = scsi_dh_handler_attach(sdev, scsi_dh);
+ } else {
+ scsi_dh = sdev->scsi_dh_data->scsi_dh;
+ if (!strncmp(buf, "detach", 6)) {
+ /*
+ * Detach from a device handler
+ */
+ scsi_dh_handler_detach(sdev, scsi_dh);
+ err = 0;
+ } else if (!strncmp(buf, "activate", 8)) {
+ /*
+ * Activate a device handler
+ */
+ if (scsi_dh->activate)
+ err = scsi_dh->activate(sdev);
+ else
+ err = 0;
+ }
+ }
+
+ return err<0?err:count;
+}
+
+static ssize_t
+show_dh_state(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ struct scsi_device *sdev = to_scsi_device(dev);
+
+ if (!sdev->scsi_dh_data)
+ return snprintf(buf, 20, "detached\n");
+
+ return snprintf(buf, 20, "%s\n", sdev->scsi_dh_data->scsi_dh->name);
+}
+
+static struct device_attribute scsi_dh_state_attr =
+ __ATTR(dh_state, S_IRUGO | S_IWUSR, show_dh_state,
+ store_dh_state);
+
+/*
+ * scsi_dh_sysfs_attr_add - Callback for scsi_init_dh
+ */
+static int scsi_dh_sysfs_attr_add(struct device *dev, void *data)
+{
+ struct scsi_device *sdev;
+ int err;
+
+ if (!scsi_is_sdev_device(dev))
+ return 0;
+
+ sdev = to_scsi_device(dev);
+
+ err = device_create_file(&sdev->sdev_gendev,
+ &scsi_dh_state_attr);
+
+ return 0;
+}
+
+/*
+ * scsi_dh_sysfs_attr_remove - Callback for scsi_exit_dh
+ */
+static int scsi_dh_sysfs_attr_remove(struct device *dev, void *data)
+{
+ struct scsi_device *sdev;
+
+ if (!scsi_is_sdev_device(dev))
+ return 0;
+
+ sdev = to_scsi_device(dev);
+
+ device_remove_file(&sdev->sdev_gendev,
+ &scsi_dh_state_attr);
+
+ return 0;
+}
+
+/*
* scsi_dh_notifier - notifier chain callback
*/
static int scsi_dh_notifier(struct notifier_block *nb,
@@ -132,7 +224,10 @@ static int scsi_dh_notifier(struct notif
if (action == BUS_NOTIFY_ADD_DEVICE) {
err = scsi_dh_handler_attach(sdev, devinfo);
+ if (!err)
+ err = device_create_file(dev, &scsi_dh_state_attr);
} else if (action == BUS_NOTIFY_DEL_DEVICE) {
+ device_remove_file(dev, &scsi_dh_state_attr);
scsi_dh_handler_detach(sdev, NULL);
}
out:
@@ -284,11 +379,17 @@ static int __init scsi_dh_init(void)
r = bus_register_notifier(&scsi_bus_type, &scsi_dh_nb);
+ if (!r)
+ bus_for_each_dev(&scsi_bus_type, NULL, NULL,
+ scsi_dh_sysfs_attr_add);
+
return r;
}
static void __exit scsi_dh_exit(void)
{
+ bus_for_each_dev(&scsi_bus_type, NULL, NULL,
+ scsi_dh_sysfs_attr_remove);
bus_unregister_notifier(&scsi_bus_type, &scsi_dh_nb);
}
--
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