driver core: Add sysfs support for physical location of a device

When ACPI table includes _PLD fields for a device, create a new
directory (physical_location) in sysfs to share _PLD fields.

Currently without PLD information, when there are multiple of same
devices, it is hard to distinguish which device corresponds to which
physical device at which location. For example, when there are two Type
C connectors, it is hard to find out which connector corresponds to the
Type C port on the left panel versus the Type C port on the right panel.
With PLD information provided, we can determine which specific device at
which location is doing what.

_PLD output includes much more fields, but only generic fields are added
and exposed to sysfs, so that non-ACPI devices can also support it in
the future. The minimal generic fields needed for locating a device are
the following.
- panel
- vertical_position
- horizontal_position
- dock
- lid

Signed-off-by: Won Chung <wonchung@google.com>
Link: https://lore.kernel.org/r/20220314195458.271430-1-wonchung@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/base/physical_location.h b/drivers/base/physical_location.h
new file mode 100644
index 000000000000..82cde9f1b161
--- /dev/null
+++ b/drivers/base/physical_location.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Device physical location support
+ *
+ * Author: Won Chung <wonchung@google.com>
+ */
+
+#include <linux/device.h>
+
+#ifdef CONFIG_ACPI
+extern bool dev_add_physical_location(struct device *dev);
+extern const struct attribute_group dev_attr_physical_location_group;
+#else
+static inline bool dev_add_physical_location(struct device *dev) { return false; };
+static const struct attribute_group dev_attr_physical_location_group = {};
+#endif