driver core: Move the "removable" attribute from USB to core

Move the "removable" attribute from USB to core in order to allow it to be
supported by other subsystem / buses. Individual buses that want to support
this attribute can populate the removable property of the device while
enumerating it with the 3 possible values -
 - "unknown"
 - "fixed"
 - "removable"
Leaving the field unchanged (i.e. "not supported") would mean that the
attribute would not show up in sysfs for that device. The UAPI (location,
symantics etc) for the attribute remains unchanged.

Move the "removable" attribute from USB to the device core so it can be
used by other subsystems / buses.

By default, devices do not have a "removable" attribute in sysfs.

If a subsystem or bus driver wants to support a "removable" attribute, it
should call device_set_removable() before calling device_register() or
device_add(), e.g.:

    device_set_removable(dev, DEVICE_REMOVABLE);
    device_register(dev);

The possible values and the resulting sysfs attribute contents are:

    DEVICE_REMOVABLE_UNKNOWN  ->  "unknown"
    DEVICE_REMOVABLE          ->  "removable"
    DEVICE_FIXED              ->  "fixed"

Convert the USB "removable" attribute to use this new device core
functionality.  There should be no user-visible change in the location or
semantics of attribute for USB devices.

Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rajat Jain <rajatja@google.com>
Link: https://lore.kernel.org/r/20210524171812.18095-1-rajatja@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/include/linux/device.h b/include/linux/device.h
index 38a2071cf776..8566fa98b239 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -351,6 +351,22 @@ enum dl_dev_state {
 };
 
 /**
+ * enum device_removable - Whether the device is removable. The criteria for a
+ * device to be classified as removable is determined by its subsystem or bus.
+ * @DEVICE_REMOVABLE_NOT_SUPPORTED: This attribute is not supported for this
+ *				    device (default).
+ * @DEVICE_REMOVABLE_UNKNOWN:  Device location is Unknown.
+ * @DEVICE_FIXED: Device is not removable by the user.
+ * @DEVICE_REMOVABLE: Device is removable by the user.
+ */
+enum device_removable {
+	DEVICE_REMOVABLE_NOT_SUPPORTED = 0, /* must be 0 */
+	DEVICE_REMOVABLE_UNKNOWN,
+	DEVICE_FIXED,
+	DEVICE_REMOVABLE,
+};
+
+/**
  * struct dev_links_info - Device data related to device links.
  * @suppliers: List of links to supplier devices.
  * @consumers: List of links to consumer devices.
@@ -431,6 +447,9 @@ struct dev_links_info {
  * 		device (i.e. the bus driver that discovered the device).
  * @iommu_group: IOMMU group the device belongs to.
  * @iommu:	Per device generic IOMMU runtime data
+ * @removable:  Whether the device can be removed from the system. This
+ *              should be set by the subsystem / bus driver that discovered
+ *              the device.
  *
  * @offline_disabled: If set, the device is permanently online.
  * @offline:	Set after successful invocation of bus type's .offline().
@@ -544,6 +563,8 @@ struct device {
 	struct iommu_group	*iommu_group;
 	struct dev_iommu	*iommu;
 
+	enum device_removable	removable;
+
 	bool			offline_disabled:1;
 	bool			offline:1;
 	bool			of_node_reused:1;
@@ -782,6 +803,22 @@ static inline bool dev_has_sync_state(struct device *dev)
 	return false;
 }
 
+static inline void dev_set_removable(struct device *dev,
+				     enum device_removable removable)
+{
+	dev->removable = removable;
+}
+
+static inline bool dev_is_removable(struct device *dev)
+{
+	return dev->removable == DEVICE_REMOVABLE;
+}
+
+static inline bool dev_removable_is_valid(struct device *dev)
+{
+	return dev->removable != DEVICE_REMOVABLE_NOT_SUPPORTED;
+}
+
 /*
  * High level routines for use by the bus drivers
  */