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Commit 4c05ae52 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by James Bottomley
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[SCSI] scsi_dh: Add 'dh_state' sysfs attribute 



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: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 765cbc6d

drivers/scsi/device_handler/scsi_dh.c

+102 −1
Original line number Diff line number Diff line
@@ -84,7 +84,7 @@ static int scsi_dh_handler_attach(struct scsi_device *sdev, 
 * @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)
@@ -102,6 +102,98 @@ static void scsi_dh_handler_detach(struct scsi_device *sdev, 
		scsi_dh->detach(sdev);

}



/*

 * 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

 */
@@ -132,7 +224,10 @@ static int scsi_dh_notifier(struct notifier_block *nb, 


	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);

}