drivers/core/of: Add symlink to device-tree from devices with an OF node (5590f319) · Commits · 戴 / test

So I've been annoyed lately with having a bunch of devices such as i2c eeproms (for use by VPDs, server world !) and other bits and pieces that I want to be able to identify from userspace, and possibly provide additional data about from FW. Basically, it boils down to correlating the sysfs device with the OF tree device node, so that user space can use device-tree info such as additional "location" or "label" (or whatever else we can come up with) propreties to identify a given device, or get some attributes of use about it, etc... Now, so far, we've done that in some subsystem in a fairly ad-hoc basis using "devspec" properties. For example, PCI creates them if it can correlate the probed device with a DT node. Some powerpc specific busses do that too. However, i2c doesn't and it would be nice to have something more generic since technically any device can have a corresponding device tree node. This patch adds an "of_node" symlink to devices that have a non-NULL dev->of_node pointer, the patch is pretty trivial and seems to work just fine for me. Signed-off-by:

Benjamin Herrenschmidt <benh@kernel.crashing.org> Acked-by:

Rob Herring <robh@kernel.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/stable/sysfs-devices

0 → 100644

+10 −0

Original line number	Diff line number	Diff line
		# Note: This documents additional properties of any device beyond what
		# is documented in Documentation/sysfs-rules.txt

		What: /sys/devices/*/of_path
		Date: February 2015
		Contact: Device Tree mailing list <devicetree@vger.kernel.org>
		Description:
		Any device associated with a device-tree node will have
		an of_path symlink pointing to the corresponding device
		node in /sys/firmware/devicetree/

drivers/base/core.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -805,8 +805,16 @@ static void cleanup_device_parent(struct device *dev)

		static int device_add_class_symlinks(struct device *dev)
		{
		struct device_node *of_node = dev_of_node(dev);
		int error;

		if (of_node) {
		error = sysfs_create_link(&dev->kobj, &of_node->kobj,"of_node");
		if (error)
		dev_warn(dev, "Error %d creating of_node link\n",error);
		/* An error here doesn't warrant bringing down the device */
		}

		if (!dev->class)
		return 0;

		@@ -814,7 +822,7 @@ static int device_add_class_symlinks(struct device *dev)
		&dev->class->p->subsys.kobj,
		"subsystem");
		if (error)
		goto out;
		goto out_devnode;

		if (dev->parent && device_is_not_partition(dev)) {
		error = sysfs_create_link(&dev->kobj, &dev->parent->kobj,
		@@ -842,12 +850,16 @@ out_device:

		out_subsys:
		sysfs_remove_link(&dev->kobj, "subsystem");
		out:
		out_devnode:
		sysfs_remove_link(&dev->kobj, "of_node");
		return error;
		}

		static void device_remove_class_symlinks(struct device *dev)
		{
		if (dev_of_node(dev))
		sysfs_remove_link(&dev->kobj, "of_node");

		if (!dev->class)
		return;

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