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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: Hannes Reinecke <hare@suse.de>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Hannes Reinecke 2008-07-17 16:52:57 -07:00 committed by James Bottomley
parent 765cbc6dad
commit 4c05ae52fc
1 changed files with 102 additions and 1 deletions
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103
drivers/scsi/device_handler/scsi_dh.c
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@ -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);
}