Commit 8fd456ec authored by Saravana Kannan's avatar Saravana Kannan Committed by Greg Kroah-Hartman
Browse files

driver core: Add state_synced sysfs file for devices that support it 



This can be used to check if a device supports sync_state() callbacks
and therefore keeps resources left on by the bootloader enabled till all
its consumers have probed.

This can also be used to check if sync_state() has been called for a
device or whether it is still trying to keep resources enabled because
they were left enabled by the bootloader and all its consumers haven't
probed yet.

Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200521191800.136035-3-saravanak@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 287905e6

Documentation/ABI/testing/sysfs-devices-state_synced

0 → 100644
+24 −0
Original line number Diff line number Diff line 
What:		/sys/devices/.../state_synced

Date:		May 2020

Contact:	Saravana Kannan <saravanak@google.com>

Description:

		The /sys/devices/.../state_synced attribute is only present for

		devices whose bus types or driver provides the .sync_state()

		callback. The number read from it (0 or 1) reflects the value

		of the device's 'state_synced' field. A value of 0 means the

		.sync_state() callback hasn't been called yet. A value of 1

		means the .sync_state() callback has been called.



		Generally, if a device has sync_state() support and has some of

		the resources it provides enabled at the time the kernel starts

		(Eg: enabled by hardware reset or bootloader or anything that

		run before the kernel starts), then it'll keep those resources

		enabled and in a state that's compatible with the state they

		were in at the start of the kernel. The device will stop doing

		this only when the sync_state() callback has been called --

		which happens only when all its consumer devices are registered

		and have probed successfully. Resources that were left disabled

		at the time the kernel starts are not affected or limited in

		any way by sync_state() callbacks.

drivers/base/dd.c

+22 −0
Original line number Diff line number Diff line
@@ -462,6 +462,18 @@ static void driver_deferred_probe_add_trigger(struct device *dev, 
		driver_deferred_probe_trigger();

}



static ssize_t state_synced_show(struct device *dev,

				 struct device_attribute *attr, char *buf)

{

	bool val;



	device_lock(dev);

	val = dev->state_synced;

	device_unlock(dev);

	return sprintf(buf, "%u\n", val);

}

static DEVICE_ATTR_RO(state_synced);



static int really_probe(struct device *dev, struct device_driver *drv)

{

	int ret = -EPROBE_DEFER;
@@ -535,9 +547,16 @@ re_probe: 
		goto dev_groups_failed;

	}



	if (dev_has_sync_state(dev) &&

	    device_create_file(dev, &dev_attr_state_synced)) {

		dev_err(dev, "state_synced sysfs add failed\n");

		goto dev_sysfs_state_synced_failed;

	}



	if (test_remove) {

		test_remove = false;



		device_remove_file(dev, &dev_attr_state_synced);

		device_remove_groups(dev, drv->dev_groups);



		if (dev->bus->remove)
@@ -567,6 +586,8 @@ re_probe: 
		 drv->bus->name, __func__, dev_name(dev), drv->name);

	goto done;



dev_sysfs_state_synced_failed:

	device_remove_groups(dev, drv->dev_groups);

dev_groups_failed:

	if (dev->bus->remove)

		dev->bus->remove(dev);
@@ -1104,6 +1125,7 @@ static void __device_release_driver(struct device *dev, struct device *parent) 


		pm_runtime_put_sync(dev);



		device_remove_file(dev, &dev_attr_state_synced);

		device_remove_groups(dev, drv->dev_groups);



		if (dev->bus && dev->bus->remove)

CRA Git | Maintained and supported by SUSTech CRA and CCSE