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, 28 insertions, 0 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 628e33939aca..f0a2331c71a0 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2405,6 +2405,25 @@ static ssize_t online_store(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RW(online);
 
+static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	const char *loc;
+
+	switch (dev->removable) {
+	case DEVICE_REMOVABLE:
+		loc = "removable";
+		break;
+	case DEVICE_FIXED:
+		loc = "fixed";
+		break;
+	default:
+		loc = "unknown";
+	}
+	return sysfs_emit(buf, "%s\n", loc);
+}
+static DEVICE_ATTR_RO(removable);
+
 int device_add_groups(struct device *dev, const struct attribute_group **groups)
 {
 	return sysfs_create_groups(&dev->kobj, groups);
@@ -2582,8 +2601,16 @@ static int device_add_attrs(struct device *dev)
 			goto err_remove_dev_online;
 	}
 
+	if (dev_removable_is_valid(dev)) {
+		error = device_create_file(dev, &dev_attr_removable);
+		if (error)
+			goto err_remove_dev_waiting_for_supplier;
+	}
+
 	return 0;
 
+ err_remove_dev_waiting_for_supplier:
+	device_remove_file(dev, &dev_attr_waiting_for_supplier);
  err_remove_dev_online:
 	device_remove_file(dev, &dev_attr_online);
  err_remove_dev_groups:
@@ -2603,6 +2630,7 @@ static void device_remove_attrs(struct device *dev)
 	struct class *class = dev->class;
 	const struct device_type *type = dev->type;
 
+	device_remove_file(dev, &dev_attr_removable);
 	device_remove_file(dev, &dev_attr_waiting_for_supplier);
 	device_remove_file(dev, &dev_attr_online);
 	device_remove_groups(dev, dev->groups);