[PATCH v3] driver core: Add sysfs support for physical location of a device

[Won Chung]

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@xxxxxxxxxx>
---

Changes from v2
- Use sysfs_emit to create files.
- Correct mix of spaces and tabs.

Changes from v1
- Correct directory names in Documentation.
- Clarify namings in core.c

 .../testing/sysfs-devices-physical_location   |  42 ++++++
 drivers/base/core.c                           | 139 ++++++++++++++++++
 include/linux/device.h                        |  73 +++++++++
 3 files changed, 254 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-physical_location

diff --git a/Documentation/ABI/testing/sysfs-devices-physical_location b/Documentation/ABI/testing/sysfs-devices-physical_location
new file mode 100644
index 000000000000..202324b87083
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-physical_location
@@ -0,0 +1,42 @@
+What:		/sys/devices/.../physical_location
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		This directory contains information on physical location of
+		the device connection point with respect to the system's
+		housing.
+
+What:		/sys/devices/.../physical_location/panel
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		Describes which panel surface of the system’s housing the
+		device connection point resides on.
+
+What:		/sys/devices/.../physical_location/vertical_position
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		Describes vertical position of the device connection point on
+		the panel surface.
+
+What:		/sys/devices/.../physical_location/horizontal_position
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		Describes horizontal position of the device connection point on
+		the panel surface.
+
+What:		/sys/devices/.../physical_location/dock
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		"Yes" if the device connection point resides in a docking
+		station or a port replicator. "No" otherwise.
+
+What:		/sys/devices/.../physical_location/lid
+Date:		March 2022
+Contact:	Won Chung <wonchung@xxxxxxxxxx>
+Description:
+		"Yes" if the device connection point resides on the lid of
+		laptop system. "No" otherwise.
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 7bb957b11861..9cfa71ad21f3 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2466,6 +2466,136 @@ static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(removable);
 
+static int dev_add_physical_location(struct device *dev)
+{
+#if defined(CONFIG_ACPI)
+	struct acpi_pld_info *pld;
+	acpi_status status;
+
+	if (!has_acpi_companion(dev))
+		return 0;
+
+	status = acpi_get_physical_device_location(ACPI_HANDLE(dev), &pld);
+	if (ACPI_FAILURE(status) || !pld)
+		return 0;
+
+	dev->location = (struct device_location) {
+		.panel = pld->panel,
+		.vertical_position = pld->vertical_position,
+		.horizontal_position = pld->horizontal_position,
+		.dock = pld->dock,
+		.lid = pld->lid,
+	};
+
+	return 1;
+#else
+	return 0;
+#endif
+}
+
+static ssize_t panel_show(struct device *dev, struct device_attribute *attr,
+	char *buf)
+{
+	const char *panel;
+
+	switch (dev->location.panel) {
+	case DEVICE_PANEL_TOP:
+		panel = "top";
+		break;
+	case DEVICE_PANEL_BOTTOM:
+		panel = "bottom";
+		break;
+	case DEVICE_PANEL_LEFT:
+		panel = "left";
+		break;
+	case DEVICE_PANEL_RIGHT:
+		panel = "right";
+		break;
+	case DEVICE_PANEL_FRONT:
+		panel = "front";
+		break;
+	case DEVICE_PANEL_BACK:
+		panel = "back";
+		break;
+	default:
+		panel = "unknown";
+	}
+	return sysfs_emit(buf, "%s\n", panel);
+}
+static DEVICE_ATTR_RO(panel);
+
+static ssize_t vertical_position_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const char *vertical_position;
+
+	switch (dev->location.vertical_position) {
+	case DEVICE_VERT_POS_UPPER:
+		vertical_position = "upper";
+		break;
+	case DEVICE_VERT_POS_CENTER:
+		vertical_position = "center";
+		break;
+	case DEVICE_VERT_POS_LOWER:
+		vertical_position = "lower";
+		break;
+	default:
+		vertical_position = "unknown";
+	}
+	return sysfs_emit(buf, "%s\n", vertical_position);
+}
+static DEVICE_ATTR_RO(vertical_position);
+
+static ssize_t horizontal_position_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const char *horizontal_position;
+
+	switch (dev->location.horizontal_position) {
+	case DEVICE_HORI_POS_LEFT:
+		horizontal_position = "left";
+		break;
+	case DEVICE_HORI_POS_CENTER:
+		horizontal_position = "center";
+		break;
+	case DEVICE_HORI_POS_RIGHT:
+		horizontal_position = "right";
+		break;
+	default:
+		horizontal_position = "unknown";
+	}
+	return sysfs_emit(buf, "%s\n", horizontal_position);
+}
+static DEVICE_ATTR_RO(horizontal_position);
+
+static ssize_t dock_show(struct device *dev, struct device_attribute *attr,
+	char *buf)
+{
+	return sysfs_emit(buf, "%s\n", dev->location.dock ? "yes" : "no");
+}
+static DEVICE_ATTR_RO(dock);
+
+static ssize_t lid_show(struct device *dev, struct device_attribute *attr,
+	char *buf)
+{
+	return sysfs_emit(buf, "%s\n", dev->location.lid ? "yes" : "no");
+}
+static DEVICE_ATTR_RO(lid);
+
+static struct attribute *dev_attr_physical_location[] = {
+	&dev_attr_panel.attr,
+	&dev_attr_vertical_position.attr,
+	&dev_attr_horizontal_position.attr,
+	&dev_attr_dock.attr,
+	&dev_attr_lid.attr,
+	NULL,
+};
+
+static const struct attribute_group dev_attr_physical_location_group = {
+	.name = "physical_location",
+	.attrs = dev_attr_physical_location,
+};
+
 int device_add_groups(struct device *dev, const struct attribute_group **groups)
 {
 	return sysfs_create_groups(&dev->kobj, groups);
@@ -2649,8 +2779,17 @@ static int device_add_attrs(struct device *dev)
 			goto err_remove_dev_waiting_for_supplier;
 	}
 
+	if (dev_add_physical_location(dev)) {
+		error = device_add_group(dev,
+			&dev_attr_physical_location_group);
+		if (error)
+			goto err_remove_dev_physical_location;
+	}
+
 	return 0;
 
+ err_remove_dev_physical_location:
+	device_remove_group(dev, &dev_attr_physical_location_group);
  err_remove_dev_waiting_for_supplier:
 	device_remove_file(dev, &dev_attr_waiting_for_supplier);
  err_remove_dev_online:
diff --git a/include/linux/device.h b/include/linux/device.h
index 93459724dcde..424be9cb735e 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -386,6 +386,75 @@ struct dev_msi_info {
 #endif
 };
 
+/**
+ * enum device_location_panel - Describes which panel surface of the system's
+ * housing the device connection point resides on.
+ * @DEVICE_PANEL_TOP: Device connection point is on the top panel.
+ * @DEVICE_PANEL_BOTTOM: Device connection point is on the bottom panel.
+ * @DEVICE_PANEL_LEFT: Device connection point is on the left panel.
+ * @DEVICE_PANEL_RIGHT: Device connection point is on the right panel.
+ * @DEVICE_PANEL_FRONT: Device connection point is on the front panel.
+ * @DEVICE_PANEL_BACK: Device connection point is on the back panel.
+ * @DEVICE_PANEL_UNKNOWN: The panel with device connection point is unknown.
+ */
+enum device_location_panel {
+	DEVICE_PANEL_TOP,
+	DEVICE_PANEL_BOTTOM,
+	DEVICE_PANEL_LEFT,
+	DEVICE_PANEL_RIGHT,
+	DEVICE_PANEL_FRONT,
+	DEVICE_PANEL_BACK,
+	DEVICE_PANEL_UNKNOWN,
+};
+
+/**
+ * enum device_location_vertical_position - Describes vertical position of the
+ * device connection point on the panel surface.
+ * @DEVICE_VERT_POS_UPPER: Device connection point is at upper part of panel.
+ * @DEVICE_VERT_POS_CENTER: Device connection point is at center part of panel.
+ * @DEVICE_VERT_POS_LOWER: Device connection point is at lower part of panel.
+ */
+enum device_location_vertical_position {
+	DEVICE_VERT_POS_UPPER,
+	DEVICE_VERT_POS_CENTER,
+	DEVICE_VERT_POS_LOWER,
+};
+
+/**
+ * enum device_location_horizontal_position - Describes horizontal position of
+ * the device connection point on the panel surface.
+ * @DEVICE_HORI_POS_LEFT: Device connection point is at left part of panel.
+ * @DEVICE_HORI_POS_CENTER: Device connection point is at center part of panel.
+ * @DEVICE_HORI_POS_RIGHT: Device connection point is at right part of panel.
+ */
+enum device_location_horizontal_position {
+	DEVICE_HORI_POS_LEFT,
+	DEVICE_HORI_POS_CENTER,
+	DEVICE_HORI_POS_RIGHT,
+};
+
+/**
+ * struct device_location - Device data related to physical location of the
+ * device connection point.
+ * @panel: Panel surface of the system's housing that the device connection
+ *         point resides on.
+ * @vertical_position: Vertical position of the device connection point within
+ *                     the panel.
+ * @horizontal_position: Horizontal position of the device connection point
+ *                       within the panel.
+ * @dock: Set if the device connection point resides in a docking station or
+ *        port replicator.
+ * @lid: Set if this device connection point resides on the lid of laptop
+ *       system.
+ */
+struct device_location {
+	enum device_location_panel panel;
+	enum device_location_vertical_position vertical_position;
+	enum device_location_horizontal_position horizontal_position;
+	bool dock;
+	bool lid;
+};
+
 /**
  * struct device - The basic device structure
  * @parent:	The device's "parent" device, the device to which it is attached.
@@ -456,6 +525,8 @@ struct dev_msi_info {
  * @removable:  Whether the device can be removed from the system. This
  *              should be set by the subsystem / bus driver that discovered
  *              the device.
+ * @location:	Describes physical location of the device connection point in
+ *		the system housing.
  *
  * @offline_disabled: If set, the device is permanently online.
  * @offline:	Set after successful invocation of bus type's .offline().
@@ -569,6 +640,8 @@ struct device {
 
 	enum device_removable	removable;
 
+	struct device_location	location;
+
 	bool			offline_disabled:1;
 	bool			offline:1;
 	bool			of_node_reused:1;
-- 
2.35.1.616.g0bdcbb4464-goog