[linux-2.6-block.git] / drivers / scsi / device_handler / scsi_dh.c

/*
 * SCSI device handler infrastruture.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright IBM Corporation, 2007
 *      Authors:
 *               Chandra Seetharaman <sekharan@us.ibm.com>
 *               Mike Anderson <andmike@linux.vnet.ibm.com>
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <scsi/scsi_dh.h>
#include "../scsi_priv.h"

static DEFINE_SPINLOCK(list_lock);
static LIST_HEAD(scsi_dh_list);

static struct scsi_device_handler *__scsi_dh_lookup(const char *name)
{
	struct scsi_device_handler *tmp, *found = NULL;

	spin_lock(&list_lock);
	list_for_each_entry(tmp, &scsi_dh_list, list) {
		if (!strncmp(tmp->name, name, strlen(tmp->name))) {
			found = tmp;
			break;
		}
	}
	spin_unlock(&list_lock);
	return found;
}

static struct scsi_device_handler *scsi_dh_lookup(const char *name)
{
	struct scsi_device_handler *dh;

	dh = __scsi_dh_lookup(name);
	if (!dh) {
		request_module(name);
		dh = __scsi_dh_lookup(name);
	}

	return dh;
}

/*
 * device_handler_match_function - Match a device handler to a device
 * @sdev - SCSI device to be tested
 *
 * Tests @sdev against the match function of all registered device_handler.
 * Returns the found device handler or NULL if not found.
 */
static struct scsi_device_handler *
device_handler_match_function(struct scsi_device *sdev)
{
	struct scsi_device_handler *tmp_dh, *found_dh = NULL;

	spin_lock(&list_lock);
	list_for_each_entry(tmp_dh, &scsi_dh_list, list) {
		if (tmp_dh->match && tmp_dh->match(sdev)) {
			found_dh = tmp_dh;
			break;
		}
	}
	spin_unlock(&list_lock);
	return found_dh;
}

/*
 * device_handler_match - Attach a device handler to a device
 * @scsi_dh - The device handler to match against or NULL
 * @sdev - SCSI device to be tested against @scsi_dh
 *
 * Tests @sdev against the device handler @scsi_dh or against
 * all registered device_handler if @scsi_dh == NULL.
 * Returns the found device handler or NULL if not found.
 */
static struct scsi_device_handler *
device_handler_match(struct scsi_device_handler *scsi_dh,
		     struct scsi_device *sdev)
{
	struct scsi_device_handler *found_dh;

	found_dh = device_handler_match_function(sdev);

	if (scsi_dh && found_dh != scsi_dh)
		found_dh = NULL;

	return found_dh;
}

/*
 * scsi_dh_handler_attach - Attach a device handler to a device
 * @sdev - SCSI device the device handler should attach to
 * @scsi_dh - The device handler to attach
 */
static int scsi_dh_handler_attach(struct scsi_device *sdev,
				  struct scsi_device_handler *scsi_dh)
{
	struct scsi_dh_data *d;

	if (!try_module_get(scsi_dh->module))
		return -EINVAL;

	d = scsi_dh->attach(sdev);
	if (IS_ERR(d)) {
		sdev_printk(KERN_ERR, sdev, "%s: Attach failed (%ld)\n",
			    scsi_dh->name, PTR_ERR(d));
		module_put(scsi_dh->module);
		return PTR_ERR(d);
	}

	d->scsi_dh = scsi_dh;
	d->sdev = sdev;

	spin_lock_irq(sdev->request_queue->queue_lock);
	sdev->scsi_dh_data = d;
	spin_unlock_irq(sdev->request_queue->queue_lock);
	return 0;
}

/*
 * scsi_dh_handler_detach - Detach a device handler from a device
 * @sdev - SCSI device the device handler should be detached from
 */
static void scsi_dh_handler_detach(struct scsi_device *sdev)
{
	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
	struct scsi_device_handler *scsi_dh = scsi_dh_data->scsi_dh;

	scsi_dh->detach(sdev);

	spin_lock_irq(sdev->request_queue->queue_lock);
	sdev->scsi_dh_data = NULL;
	spin_unlock_irq(sdev->request_queue->queue_lock);

	sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", scsi_dh->name);
	module_put(scsi_dh->module);
}

/*
 * 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->sdev_state == SDEV_CANCEL ||
	    sdev->sdev_state == SDEV_DEL)
		return -ENODEV;

	if (!sdev->scsi_dh_data) {
		/*
		 * Attach to a device handler
		 */
		scsi_dh = scsi_dh_lookup(buf);
		if (!scsi_dh)
			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);
			err = 0;
		} else if (!strncmp(buf, "activate", 8)) {
			/*
			 * Activate a device handler
			 */
			if (scsi_dh->activate)
				err = scsi_dh->activate(sdev, NULL, NULL);
			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,
			    unsigned long action, void *data)
{
	struct device *dev = data;
	struct scsi_device *sdev;
	int err = 0;
	struct scsi_device_handler *devinfo = NULL;

	if (!scsi_is_sdev_device(dev))
		return 0;

	sdev = to_scsi_device(dev);

	if (action == BUS_NOTIFY_ADD_DEVICE) {
		err = device_create_file(dev, &scsi_dh_state_attr);
		/* don't care about err */
		devinfo = device_handler_match(NULL, sdev);
		if (devinfo)
			err = scsi_dh_handler_attach(sdev, devinfo);
	} else if (action == BUS_NOTIFY_DEL_DEVICE) {
		device_remove_file(dev, &scsi_dh_state_attr);
		if (sdev->scsi_dh_data)
			scsi_dh_handler_detach(sdev);
	}
	return err;
}

/*
 * scsi_dh_notifier_add - Callback for scsi_register_device_handler
 */
static int scsi_dh_notifier_add(struct device *dev, void *data)
{
	struct scsi_device_handler *scsi_dh = data;
	struct scsi_device *sdev;

	if (!scsi_is_sdev_device(dev))
		return 0;

	if (!get_device(dev))
		return 0;

	sdev = to_scsi_device(dev);

	if (device_handler_match(scsi_dh, sdev))
		scsi_dh_handler_attach(sdev, scsi_dh);

	put_device(dev);

	return 0;
}

/*
 * scsi_dh_notifier_remove - Callback for scsi_unregister_device_handler
 */
static int scsi_dh_notifier_remove(struct device *dev, void *data)
{
	struct scsi_device_handler *scsi_dh = data;
	struct scsi_device *sdev;

	if (!scsi_is_sdev_device(dev))
		return 0;

	if (!get_device(dev))
		return 0;

	sdev = to_scsi_device(dev);

	if (sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh == scsi_dh)
		scsi_dh_handler_detach(sdev);

	put_device(dev);

	return 0;
}

/*
 * scsi_register_device_handler - register a device handler personality
 *      module.
 * @scsi_dh - device handler to be registered.
 *
 * Returns 0 on success, -EBUSY if handler already registered.
 */
int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
{
	if (__scsi_dh_lookup(scsi_dh->name))
		return -EBUSY;

	if (!scsi_dh->attach || !scsi_dh->detach)
		return -EINVAL;

	spin_lock(&list_lock);
	list_add(&scsi_dh->list, &scsi_dh_list);
	spin_unlock(&list_lock);

	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh, scsi_dh_notifier_add);
	printk(KERN_INFO "%s: device handler registered\n", scsi_dh->name);

	return SCSI_DH_OK;
}
EXPORT_SYMBOL_GPL(scsi_register_device_handler);

/*
 * scsi_unregister_device_handler - register a device handler personality
 *      module.
 * @scsi_dh - device handler to be unregistered.
 *
 * Returns 0 on success, -ENODEV if handler not registered.
 */
int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)
{

	if (!__scsi_dh_lookup(scsi_dh->name))
		return -ENODEV;

	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh,
			 scsi_dh_notifier_remove);

	spin_lock(&list_lock);
	list_del(&scsi_dh->list);
	spin_unlock(&list_lock);
	printk(KERN_INFO "%s: device handler unregistered\n", scsi_dh->name);

	return SCSI_DH_OK;
}
EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);

/*
 * scsi_dh_activate - activate the path associated with the scsi_device
 *      corresponding to the given request queue.
 *     Returns immediately without waiting for activation to be completed.
 * @q    - Request queue that is associated with the scsi_device to be
 *         activated.
 * @fn   - Function to be called upon completion of the activation.
 *         Function fn is called with data (below) and the error code.
 *         Function fn may be called from the same calling context. So,
 *         do not hold the lock in the caller which may be needed in fn.
 * @data - data passed to the function fn upon completion.
 *
 */
int scsi_dh_activate(struct request_queue *q, activate_complete fn, void *data)
{
	int err = 0;
	unsigned long flags;
	struct scsi_device *sdev;
	struct scsi_device_handler *scsi_dh = NULL;
	struct device *dev = NULL;

	spin_lock_irqsave(q->queue_lock, flags);
	sdev = q->queuedata;
	if (!sdev) {
		spin_unlock_irqrestore(q->queue_lock, flags);
		err = SCSI_DH_NOSYS;
		if (fn)
			fn(data, err);
		return err;
	}

	if (sdev->scsi_dh_data)
		scsi_dh = sdev->scsi_dh_data->scsi_dh;
	dev = get_device(&sdev->sdev_gendev);
	if (!scsi_dh || !dev ||
	    sdev->sdev_state == SDEV_CANCEL ||
	    sdev->sdev_state == SDEV_DEL)
		err = SCSI_DH_NOSYS;
	if (sdev->sdev_state == SDEV_OFFLINE)
		err = SCSI_DH_DEV_OFFLINED;
	spin_unlock_irqrestore(q->queue_lock, flags);

	if (err) {
		if (fn)
			fn(data, err);
		goto out;
	}

	if (scsi_dh->activate)
		err = scsi_dh->activate(sdev, fn, data);
out:
	put_device(dev);
	return err;
}
EXPORT_SYMBOL_GPL(scsi_dh_activate);

/*
 * scsi_dh_set_params - set the parameters for the device as per the
 *      string specified in params.
 * @q - Request queue that is associated with the scsi_device for
 *      which the parameters to be set.
 * @params - parameters in the following format
 *      "no_of_params\0param1\0param2\0param3\0...\0"
 *      for example, string for 2 parameters with value 10 and 21
 *      is specified as "2\010\021\0".
 */
int scsi_dh_set_params(struct request_queue *q, const char *params)
{
	int err = -SCSI_DH_NOSYS;
	unsigned long flags;
	struct scsi_device *sdev;
	struct scsi_device_handler *scsi_dh = NULL;

	spin_lock_irqsave(q->queue_lock, flags);
	sdev = q->queuedata;
	if (sdev && sdev->scsi_dh_data)
		scsi_dh = sdev->scsi_dh_data->scsi_dh;
	if (scsi_dh && scsi_dh->set_params && get_device(&sdev->sdev_gendev))
		err = 0;
	spin_unlock_irqrestore(q->queue_lock, flags);

	if (err)
		return err;
	err = scsi_dh->set_params(sdev, params);
	put_device(&sdev->sdev_gendev);
	return err;
}
EXPORT_SYMBOL_GPL(scsi_dh_set_params);

/*
 * scsi_dh_attach - Attach device handler
 * @q - Request queue that is associated with the scsi_device
 *      the handler should be attached to
 * @name - name of the handler to attach
 */
int scsi_dh_attach(struct request_queue *q, const char *name)
{
	unsigned long flags;
	struct scsi_device *sdev;
	struct scsi_device_handler *scsi_dh;
	int err = 0;

	scsi_dh = scsi_dh_lookup(name);
	if (!scsi_dh)
		return -EINVAL;

	spin_lock_irqsave(q->queue_lock, flags);
	sdev = q->queuedata;
	if (!sdev || !get_device(&sdev->sdev_gendev))
		err = -ENODEV;
	spin_unlock_irqrestore(q->queue_lock, flags);

	if (err)
		return err;

	if (sdev->scsi_dh_data) {
		if (sdev->scsi_dh_data->scsi_dh != scsi_dh)
			err = -EBUSY;
		goto out_put_device;
	}

	err = scsi_dh_handler_attach(sdev, scsi_dh);

out_put_device:
	put_device(&sdev->sdev_gendev);
	return err;
}
EXPORT_SYMBOL_GPL(scsi_dh_attach);

/*
 * scsi_dh_attached_handler_name - Get attached device handler's name
 * @q - Request queue that is associated with the scsi_device
 *      that may have a device handler attached
 * @gfp - the GFP mask used in the kmalloc() call when allocating memory
 *
 * Returns name of attached handler, NULL if no handler is attached.
 * Caller must take care to free the returned string.
 */
const char *scsi_dh_attached_handler_name(struct request_queue *q, gfp_t gfp)
{
	unsigned long flags;
	struct scsi_device *sdev;
	const char *handler_name = NULL;

	spin_lock_irqsave(q->queue_lock, flags);
	sdev = q->queuedata;
	if (!sdev || !get_device(&sdev->sdev_gendev))
		sdev = NULL;
	spin_unlock_irqrestore(q->queue_lock, flags);

	if (!sdev)
		return NULL;

	if (sdev->scsi_dh_data)
		handler_name = kstrdup(sdev->scsi_dh_data->scsi_dh->name, gfp);

	put_device(&sdev->sdev_gendev);
	return handler_name;
}
EXPORT_SYMBOL_GPL(scsi_dh_attached_handler_name);

static struct notifier_block scsi_dh_nb = {
	.notifier_call = scsi_dh_notifier
};

static int __init scsi_dh_init(void)
{
	int r;

	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);
}

module_init(scsi_dh_init);
module_exit(scsi_dh_exit);

MODULE_DESCRIPTION("SCSI device handler");
MODULE_AUTHOR("Chandra Seetharaman <sekharan@us.ibm.com>");
MODULE_LICENSE("GPL");
Commit	Line	Data
a6a8d9f8 CS	1	/*
	2	* SCSI device handler infrastruture.
	3	*
	4	* This program is free software; you can redistribute it and/or modify it
	5	* under the terms of the GNU General Public License as published by the
	6	* Free Software Foundation; either version 2 of the License, or (at your
	7	* option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful, but
	10	* WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	12	* General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License along
	15	* with this program; if not, write to the Free Software Foundation, Inc.,
	16	* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
	18	* Copyright IBM Corporation, 2007
	19	* Authors:
	20	* Chandra Seetharaman <sekharan@us.ibm.com>
	21	* Mike Anderson <andmike@linux.vnet.ibm.com>
	22	*/
	23
5a0e3ad6	24	#include <linux/slab.h>
acf3368f	25	#include <linux/module.h>
a6a8d9f8 CS	26	#include <scsi/scsi_dh.h>
	27	#include "../scsi_priv.h"
	28
	29	static DEFINE_SPINLOCK(list_lock);
	30	static LIST_HEAD(scsi_dh_list);
	31
566079c8	32	static struct scsi_device_handler __scsi_dh_lookup(const char name)
a6a8d9f8 CS	33	{
	34	struct scsi_device_handler tmp, found = NULL;
	35
	36	spin_lock(&list_lock);
	37	list_for_each_entry(tmp, &scsi_dh_list, list) {
765cbc6d	38	if (!strncmp(tmp->name, name, strlen(tmp->name))) {
a6a8d9f8 CS	39	found = tmp;
	40	break;
	41	}
	42	}
	43	spin_unlock(&list_lock);
	44	return found;
	45	}
	46
566079c8 CH	47	static struct scsi_device_handler scsi_dh_lookup(const char name)
	48	{
	49	struct scsi_device_handler *dh;
	50
	51	dh = __scsi_dh_lookup(name);
	52	if (!dh) {
	53	request_module(name);
	54	dh = __scsi_dh_lookup(name);
	55	}
	56
	57	return dh;
	58	}
	59
6c3633d0 HR	60	/*
	61	* device_handler_match_function - Match a device handler to a device
	62	* @sdev - SCSI device to be tested
	63	*
	64	* Tests @sdev against the match function of all registered device_handler.
	65	* Returns the found device handler or NULL if not found.
	66	*/
	67	static struct scsi_device_handler *
	68	device_handler_match_function(struct scsi_device *sdev)
	69	{
	70	struct scsi_device_handler tmp_dh, found_dh = NULL;
	71
	72	spin_lock(&list_lock);
	73	list_for_each_entry(tmp_dh, &scsi_dh_list, list) {
	74	if (tmp_dh->match && tmp_dh->match(sdev)) {
	75	found_dh = tmp_dh;
	76	break;
	77	}
	78	}
	79	spin_unlock(&list_lock);
	80	return found_dh;
	81	}
	82
7c32c7a2 HR	83	/*
	84	* device_handler_match - Attach a device handler to a device
	85	* @scsi_dh - The device handler to match against or NULL
	86	* @sdev - SCSI device to be tested against @scsi_dh
	87	*
	88	* Tests @sdev against the device handler @scsi_dh or against
	89	* all registered device_handler if @scsi_dh == NULL.
	90	* Returns the found device handler or NULL if not found.
	91	*/
	92	static struct scsi_device_handler *
	93	device_handler_match(struct scsi_device_handler *scsi_dh,
	94	struct scsi_device *sdev)
	95	{
6c3633d0	96	struct scsi_device_handler *found_dh;
7c32c7a2	97
6c3633d0	98	found_dh = device_handler_match_function(sdev);
7c32c7a2	99
940d7faa PJ	100	if (scsi_dh && found_dh != scsi_dh)
940d7faa PJ	101	found_dh = NULL;
7c32c7a2 HR	102
7c32c7a2 HR	103	return found_dh;
a6a8d9f8 CS	104	}
	105
	106	/*
765cbc6d HR	107	* scsi_dh_handler_attach - Attach a device handler to a device
	108	* @sdev - SCSI device the device handler should attach to
	109	* @scsi_dh - The device handler to attach
	110	*/
	111	static int scsi_dh_handler_attach(struct scsi_device *sdev,
	112	struct scsi_device_handler *scsi_dh)
	113	{
1d520328	114	struct scsi_dh_data *d;
765cbc6d	115
1f12ffa5 CH	116	if (!try_module_get(scsi_dh->module))
1f12ffa5 CH	117	return -EINVAL;
27c888f0	118
1d520328 CH	119	d = scsi_dh->attach(sdev);
	120	if (IS_ERR(d)) {
	121	sdev_printk(KERN_ERR, sdev, "%s: Attach failed (%ld)\n",
	122	scsi_dh->name, PTR_ERR(d));
1f12ffa5	123	module_put(scsi_dh->module);
1d520328	124	return PTR_ERR(d);
6c10db72	125	}
1f12ffa5	126
1d520328	127	d->scsi_dh = scsi_dh;
1d520328 CH	128	d->sdev = sdev;
	129
	130	spin_lock_irq(sdev->request_queue->queue_lock);
	131	sdev->scsi_dh_data = d;
	132	spin_unlock_irq(sdev->request_queue->queue_lock);
	133	return 0;
765cbc6d HR	134	}
765cbc6d HR	135
1bab0de0 CH	136	/*
	137	* scsi_dh_handler_detach - Detach a device handler from a device
	138	* @sdev - SCSI device the device handler should be detached from
	139	*/
	140	static void scsi_dh_handler_detach(struct scsi_device *sdev)
6c10db72	141	{
1bab0de0	142	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
27c888f0	143	struct scsi_device_handler *scsi_dh = scsi_dh_data->scsi_dh;
1d520328	144
28072ad5 MC	145	scsi_dh->detach(sdev);
28072ad5 MC	146
1d520328 CH	147	spin_lock_irq(sdev->request_queue->queue_lock);
	148	sdev->scsi_dh_data = NULL;
	149	spin_unlock_irq(sdev->request_queue->queue_lock);
27c888f0	150
1d520328	151	sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", scsi_dh->name);
27c888f0	152	module_put(scsi_dh->module);
6c10db72 CS	153	}
6c10db72 CS	154
4c05ae52 HR	155	/*
	156	* Functions for sysfs attribute 'dh_state'
	157	*/
	158	static ssize_t
	159	store_dh_state(struct device dev, struct device_attribute attr,
	160	const char *buf, size_t count)
	161	{
	162	struct scsi_device *sdev = to_scsi_device(dev);
	163	struct scsi_device_handler *scsi_dh;
	164	int err = -EINVAL;
	165
6bc8d2a0 HR	166	if (sdev->sdev_state == SDEV_CANCEL \|\|
	167	sdev->sdev_state == SDEV_DEL)
	168	return -ENODEV;
	169
4c05ae52 HR	170	if (!sdev->scsi_dh_data) {
	171	/*
	172	* Attach to a device handler
	173	*/
566079c8 CH	174	scsi_dh = scsi_dh_lookup(buf);
566079c8 CH	175	if (!scsi_dh)
4c05ae52 HR	176	return err;
	177	err = scsi_dh_handler_attach(sdev, scsi_dh);
	178	} else {
	179	scsi_dh = sdev->scsi_dh_data->scsi_dh;
	180	if (!strncmp(buf, "detach", 6)) {
	181	/*
	182	* Detach from a device handler
	183	*/
1bab0de0	184	scsi_dh_handler_detach(sdev);
4c05ae52 HR	185	err = 0;
	186	} else if (!strncmp(buf, "activate", 8)) {
	187	/*
	188	* Activate a device handler
	189	*/
	190	if (scsi_dh->activate)
3ae31f6a	191	err = scsi_dh->activate(sdev, NULL, NULL);
4c05ae52 HR	192	else
	193	err = 0;
	194	}
	195	}
	196
	197	return err<0?err:count;
	198	}
	199
	200	static ssize_t
	201	show_dh_state(struct device dev, struct device_attribute attr, char *buf)
	202	{
	203	struct scsi_device *sdev = to_scsi_device(dev);
	204
	205	if (!sdev->scsi_dh_data)
	206	return snprintf(buf, 20, "detached\n");
	207
	208	return snprintf(buf, 20, "%s\n", sdev->scsi_dh_data->scsi_dh->name);
	209	}
	210
	211	static struct device_attribute scsi_dh_state_attr =
	212	__ATTR(dh_state, S_IRUGO \| S_IWUSR, show_dh_state,
	213	store_dh_state);
	214
	215	/*
	216	* scsi_dh_sysfs_attr_add - Callback for scsi_init_dh
	217	*/
	218	static int scsi_dh_sysfs_attr_add(struct device dev, void data)
	219	{
	220	struct scsi_device *sdev;
	221	int err;
	222
	223	if (!scsi_is_sdev_device(dev))
	224	return 0;
	225
	226	sdev = to_scsi_device(dev);
	227
	228	err = device_create_file(&sdev->sdev_gendev,
	229	&scsi_dh_state_attr);
	230
	231	return 0;
	232	}
	233
	234	/*
	235	* scsi_dh_sysfs_attr_remove - Callback for scsi_exit_dh
	236	*/
	237	static int scsi_dh_sysfs_attr_remove(struct device dev, void data)
	238	{
	239	struct scsi_device *sdev;
	240
	241	if (!scsi_is_sdev_device(dev))
	242	return 0;
	243
	244	sdev = to_scsi_device(dev);
	245
	246	device_remove_file(&sdev->sdev_gendev,
	247	&scsi_dh_state_attr);
	248
	249	return 0;
	250	}
	251
765cbc6d HR	252	/*
	253	* scsi_dh_notifier - notifier chain callback
	254	*/
	255	static int scsi_dh_notifier(struct notifier_block *nb,
	256	unsigned long action, void *data)
	257	{
	258	struct device *dev = data;
	259	struct scsi_device *sdev;
	260	int err = 0;
7c32c7a2	261	struct scsi_device_handler *devinfo = NULL;
765cbc6d HR	262
	263	if (!scsi_is_sdev_device(dev))
	264	return 0;
	265
	266	sdev = to_scsi_device(dev);
a6a8d9f8	267
765cbc6d	268	if (action == BUS_NOTIFY_ADD_DEVICE) {
5917290c CS	269	err = device_create_file(dev, &scsi_dh_state_attr);
5917290c CS	270	/* don't care about err */
7c32c7a2	271	devinfo = device_handler_match(NULL, sdev);
5917290c CS	272	if (devinfo)
5917290c CS	273	err = scsi_dh_handler_attach(sdev, devinfo);
765cbc6d	274	} else if (action == BUS_NOTIFY_DEL_DEVICE) {
4c05ae52	275	device_remove_file(dev, &scsi_dh_state_attr);
1bab0de0 CH	276	if (sdev->scsi_dh_data)
1bab0de0 CH	277	scsi_dh_handler_detach(sdev);
765cbc6d	278	}
765cbc6d	279	return err;
a6a8d9f8	280	}
a6a8d9f8	281
765cbc6d HR	282	/*
	283	* scsi_dh_notifier_add - Callback for scsi_register_device_handler
	284	*/
	285	static int scsi_dh_notifier_add(struct device dev, void data)
	286	{
	287	struct scsi_device_handler *scsi_dh = data;
	288	struct scsi_device *sdev;
	289
	290	if (!scsi_is_sdev_device(dev))
	291	return 0;
	292
	293	if (!get_device(dev))
	294	return 0;
	295
	296	sdev = to_scsi_device(dev);
	297
	298	if (device_handler_match(scsi_dh, sdev))
	299	scsi_dh_handler_attach(sdev, scsi_dh);
	300
	301	put_device(dev);
	302
	303	return 0;
	304	}
	305
	306	/*
	307	* scsi_dh_notifier_remove - Callback for scsi_unregister_device_handler
	308	*/
a6a8d9f8 CS	309	static int scsi_dh_notifier_remove(struct device dev, void data)
	310	{
	311	struct scsi_device_handler *scsi_dh = data;
765cbc6d HR	312	struct scsi_device *sdev;
	313
	314	if (!scsi_is_sdev_device(dev))
	315	return 0;
	316
	317	if (!get_device(dev))
	318	return 0;
	319
	320	sdev = to_scsi_device(dev);
	321
1bab0de0 CH	322	if (sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh == scsi_dh)
1bab0de0 CH	323	scsi_dh_handler_detach(sdev);
765cbc6d HR	324
765cbc6d HR	325	put_device(dev);
a6a8d9f8	326
a6a8d9f8 CS	327	return 0;
	328	}
	329
765cbc6d HR	330	/*
	331	* scsi_register_device_handler - register a device handler personality
	332	* module.
	333	* @scsi_dh - device handler to be registered.
	334	*
	335	* Returns 0 on success, -EBUSY if handler already registered.
	336	*/
	337	int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
	338	{
566079c8	339	if (__scsi_dh_lookup(scsi_dh->name))
765cbc6d HR	340	return -EBUSY;
765cbc6d HR	341
1f12ffa5 CH	342	if (!scsi_dh->attach \|\| !scsi_dh->detach)
	343	return -EINVAL;
	344
765cbc6d HR	345	spin_lock(&list_lock);
	346	list_add(&scsi_dh->list, &scsi_dh_list);
	347	spin_unlock(&list_lock);
940d7faa	348
765cbc6d HR	349	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh, scsi_dh_notifier_add);
	350	printk(KERN_INFO "%s: device handler registered\n", scsi_dh->name);
	351
	352	return SCSI_DH_OK;
	353	}
	354	EXPORT_SYMBOL_GPL(scsi_register_device_handler);
	355
a6a8d9f8 CS	356	/*
	357	* scsi_unregister_device_handler - register a device handler personality
	358	* module.
	359	* @scsi_dh - device handler to be unregistered.
	360	*
	361	* Returns 0 on success, -ENODEV if handler not registered.
	362	*/
	363	int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)
	364	{
7c32c7a2	365
566079c8	366	if (!__scsi_dh_lookup(scsi_dh->name))
765cbc6d	367	return -ENODEV;
a6a8d9f8 CS	368
a6a8d9f8 CS	369	bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh,
765cbc6d HR	370	scsi_dh_notifier_remove);
765cbc6d HR	371
a6a8d9f8 CS	372	spin_lock(&list_lock);
	373	list_del(&scsi_dh->list);
	374	spin_unlock(&list_lock);
765cbc6d	375	printk(KERN_INFO "%s: device handler unregistered\n", scsi_dh->name);
a6a8d9f8	376
765cbc6d	377	return SCSI_DH_OK;
a6a8d9f8 CS	378	}
	379	EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);
	380
	381	/*
	382	* scsi_dh_activate - activate the path associated with the scsi_device
	383	* corresponding to the given request queue.
3ae31f6a CS	384	* Returns immediately without waiting for activation to be completed.
	385	* @q - Request queue that is associated with the scsi_device to be
	386	* activated.
	387	* @fn - Function to be called upon completion of the activation.
	388	* Function fn is called with data (below) and the error code.
	389	* Function fn may be called from the same calling context. So,
	390	* do not hold the lock in the caller which may be needed in fn.
	391	* @data - data passed to the function fn upon completion.
	392	*
a6a8d9f8	393	*/
3ae31f6a	394	int scsi_dh_activate(struct request_queue q, activate_complete fn, void data)
a6a8d9f8 CS	395	{
	396	int err = 0;
	397	unsigned long flags;
	398	struct scsi_device *sdev;
	399	struct scsi_device_handler *scsi_dh = NULL;
0b839357	400	struct device *dev = NULL;
a6a8d9f8 CS	401
	402	spin_lock_irqsave(q->queue_lock, flags);
	403	sdev = q->queuedata;
a18a920c MB	404	if (!sdev) {
	405	spin_unlock_irqrestore(q->queue_lock, flags);
	406	err = SCSI_DH_NOSYS;
	407	if (fn)
	408	fn(data, err);
	409	return err;
	410	}
	411
	412	if (sdev->scsi_dh_data)
a6a8d9f8	413	scsi_dh = sdev->scsi_dh_data->scsi_dh;
0b839357 MS	414	dev = get_device(&sdev->sdev_gendev);
0b839357 MS	415	if (!scsi_dh \|\| !dev \|\|
db422318 MH	416	sdev->sdev_state == SDEV_CANCEL \|\|
db422318 MH	417	sdev->sdev_state == SDEV_DEL)
a6a8d9f8	418	err = SCSI_DH_NOSYS;
db422318 MH	419	if (sdev->sdev_state == SDEV_OFFLINE)
db422318 MH	420	err = SCSI_DH_DEV_OFFLINED;
a6a8d9f8 CS	421	spin_unlock_irqrestore(q->queue_lock, flags);
a6a8d9f8 CS	422
db422318 MH	423	if (err) {
	424	if (fn)
	425	fn(data, err);
0b839357	426	goto out;
db422318	427	}
a6a8d9f8 CS	428
a6a8d9f8 CS	429	if (scsi_dh->activate)
3ae31f6a	430	err = scsi_dh->activate(sdev, fn, data);
0b839357 MS	431	out:
0b839357 MS	432	put_device(dev);
a6a8d9f8 CS	433	return err;
	434	}
	435	EXPORT_SYMBOL_GPL(scsi_dh_activate);
	436
18ee70c9 CS	437	/*
	438	* scsi_dh_set_params - set the parameters for the device as per the
	439	* string specified in params.
	440	* @q - Request queue that is associated with the scsi_device for
	441	* which the parameters to be set.
	442	* @params - parameters in the following format
	443	* "no_of_params\0param1\0param2\0param3\0...\0"
	444	* for example, string for 2 parameters with value 10 and 21
	445	* is specified as "2\010\021\0".
	446	*/
	447	int scsi_dh_set_params(struct request_queue q, const char params)
	448	{
	449	int err = -SCSI_DH_NOSYS;
	450	unsigned long flags;
	451	struct scsi_device *sdev;
	452	struct scsi_device_handler *scsi_dh = NULL;
	453
	454	spin_lock_irqsave(q->queue_lock, flags);
	455	sdev = q->queuedata;
	456	if (sdev && sdev->scsi_dh_data)
	457	scsi_dh = sdev->scsi_dh_data->scsi_dh;
	458	if (scsi_dh && scsi_dh->set_params && get_device(&sdev->sdev_gendev))
	459	err = 0;
	460	spin_unlock_irqrestore(q->queue_lock, flags);
	461
	462	if (err)
	463	return err;
	464	err = scsi_dh->set_params(sdev, params);
	465	put_device(&sdev->sdev_gendev);
	466	return err;
	467	}
	468	EXPORT_SYMBOL_GPL(scsi_dh_set_params);
	469
ae11b1b3	470	/*
2a9ab40f	471	* scsi_dh_attach - Attach device handler
7e8a74b1 MS	472	* @q - Request queue that is associated with the scsi_device
7e8a74b1 MS	473	* the handler should be attached to
ae11b1b3 HR	474	* @name - name of the handler to attach
	475	*/
	476	int scsi_dh_attach(struct request_queue q, const char name)
	477	{
	478	unsigned long flags;
	479	struct scsi_device *sdev;
	480	struct scsi_device_handler *scsi_dh;
	481	int err = 0;
	482
566079c8	483	scsi_dh = scsi_dh_lookup(name);
ae11b1b3 HR	484	if (!scsi_dh)
	485	return -EINVAL;
	486
	487	spin_lock_irqsave(q->queue_lock, flags);
	488	sdev = q->queuedata;
	489	if (!sdev \|\| !get_device(&sdev->sdev_gendev))
	490	err = -ENODEV;
	491	spin_unlock_irqrestore(q->queue_lock, flags);
	492
1bab0de0 CH	493	if (err)
1bab0de0 CH	494	return err;
ae11b1b3 HR	495
ae11b1b3 HR	496	if (sdev->scsi_dh_data) {
1bab0de0 CH	497	if (sdev->scsi_dh_data->scsi_dh != scsi_dh)
	498	err = -EBUSY;
	499	goto out_put_device;
ae11b1b3	500	}
1bab0de0 CH	501
	502	err = scsi_dh_handler_attach(sdev, scsi_dh);
	503
	504	out_put_device:
ae11b1b3	505	put_device(&sdev->sdev_gendev);
1bab0de0	506	return err;
ae11b1b3	507	}
1bab0de0	508	EXPORT_SYMBOL_GPL(scsi_dh_attach);
ae11b1b3	509
7e8a74b1 MS	510	/*
	511	* scsi_dh_attached_handler_name - Get attached device handler's name
	512	* @q - Request queue that is associated with the scsi_device
	513	* that may have a device handler attached
	514	* @gfp - the GFP mask used in the kmalloc() call when allocating memory
	515	*
	516	* Returns name of attached handler, NULL if no handler is attached.
	517	* Caller must take care to free the returned string.
	518	*/
	519	const char scsi_dh_attached_handler_name(struct request_queue q, gfp_t gfp)
	520	{
	521	unsigned long flags;
	522	struct scsi_device *sdev;
	523	const char *handler_name = NULL;
	524
	525	spin_lock_irqsave(q->queue_lock, flags);
	526	sdev = q->queuedata;
	527	if (!sdev \|\| !get_device(&sdev->sdev_gendev))
	528	sdev = NULL;
	529	spin_unlock_irqrestore(q->queue_lock, flags);
	530
	531	if (!sdev)
	532	return NULL;
	533
	534	if (sdev->scsi_dh_data)
	535	handler_name = kstrdup(sdev->scsi_dh_data->scsi_dh->name, gfp);
	536
	537	put_device(&sdev->sdev_gendev);
	538	return handler_name;
	539	}
	540	EXPORT_SYMBOL_GPL(scsi_dh_attached_handler_name);
	541
765cbc6d HR	542	static struct notifier_block scsi_dh_nb = {
	543	.notifier_call = scsi_dh_notifier
	544	};
	545
	546	static int __init scsi_dh_init(void)
	547	{
	548	int r;
	549
	550	r = bus_register_notifier(&scsi_bus_type, &scsi_dh_nb);
	551
4c05ae52 HR	552	if (!r)
	553	bus_for_each_dev(&scsi_bus_type, NULL, NULL,
	554	scsi_dh_sysfs_attr_add);
	555
765cbc6d HR	556	return r;
	557	}
	558
	559	static void __exit scsi_dh_exit(void)
	560	{
4c05ae52 HR	561	bus_for_each_dev(&scsi_bus_type, NULL, NULL,
4c05ae52 HR	562	scsi_dh_sysfs_attr_remove);
765cbc6d HR	563	bus_unregister_notifier(&scsi_bus_type, &scsi_dh_nb);
	564	}
	565
	566	module_init(scsi_dh_init);
	567	module_exit(scsi_dh_exit);
	568
a6a8d9f8 CS	569	MODULE_DESCRIPTION("SCSI device handler");
	570	MODULE_AUTHOR("Chandra Seetharaman <sekharan@us.ibm.com>");
	571	MODULE_LICENSE("GPL");