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Commit 6751667a authored by Ben Hutchings's avatar Ben Hutchings Committed by Greg Kroah-Hartman
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driver core: Add deferred_probe attribute to devices in sysfs 



It is sometimes useful to know that a device is on the deferred probe
list rather than, say, not having a driver available.  Expose this
information to user-space.

Signed-off-by: default avatarBen Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent baa8809f

Documentation/ABI/testing/sysfs-devices-deferred_probe

0 → 100644
+12 −0
Original line number Diff line number Diff line 
What:		/sys/devices/.../deferred_probe

Date:		August 2016

Contact:	Ben Hutchings <ben.hutchings@codethink.co.uk>

Description:

		The /sys/devices/.../deferred_probe attribute is

		present for all devices.  If a driver detects during

		probing a device that a related device is not yet

		ready, it may defer probing of the first device.  The

		kernel will retry probing the first device after any

		other device is successfully probed.  This attribute

		reads as 1 if probing of this device is currently

		deferred, or 0 otherwise.

drivers/base/base.h

+2 −0
Original line number Diff line number Diff line
@@ -141,6 +141,8 @@ extern void device_unblock_probing(void); 
extern struct kset *devices_kset;

extern void devices_kset_move_last(struct device *dev);



extern struct device_attribute dev_attr_deferred_probe;



#if defined(CONFIG_MODULES) && defined(CONFIG_SYSFS)

extern void module_add_driver(struct module *mod, struct device_driver *drv);

extern void module_remove_driver(struct device_driver *drv);

drivers/base/core.c

+7 −0
Original line number Diff line number Diff line
@@ -1060,8 +1060,14 @@ static int device_add_attrs(struct device *dev) 
			goto err_remove_dev_groups;

	}



	error = device_create_file(dev, &dev_attr_deferred_probe);

	if (error)

		goto err_remove_online;



	return 0;



 err_remove_online:

	device_remove_file(dev, &dev_attr_online);

 err_remove_dev_groups:

	device_remove_groups(dev, dev->groups);

 err_remove_type_groups:
@@ -1079,6 +1085,7 @@ static void device_remove_attrs(struct device *dev) 
	struct class *class = dev->class;

	const struct device_type *type = dev->type;



	device_remove_file(dev, &dev_attr_deferred_probe);

	device_remove_file(dev, &dev_attr_online);

	device_remove_groups(dev, dev->groups);

drivers/base/dd.c

+13 −0
Original line number Diff line number Diff line
@@ -53,6 +53,19 @@ static LIST_HEAD(deferred_probe_pending_list); 
static LIST_HEAD(deferred_probe_active_list);

static atomic_t deferred_trigger_count = ATOMIC_INIT(0);



static ssize_t deferred_probe_show(struct device *dev,

				   struct device_attribute *attr, char *buf)

{

	bool value;



	mutex_lock(&deferred_probe_mutex);

	value = !list_empty(&dev->p->deferred_probe);

	mutex_unlock(&deferred_probe_mutex);



	return sprintf(buf, "%d\n", value);

}

DEVICE_ATTR_RO(deferred_probe);



/*

 * In some cases, like suspend to RAM or hibernation, It might be reasonable

 * to prohibit probing of devices as it could be unsafe.