[PATCH v2 1/2] driver core: Move the "removable" attribute from USB to core

From: Rajat Jain
Date: Fri Apr 23 2021 - 22:16:46 EST

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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 opt-in by setting the
supports_removable flag, and then populating the removable property
of the device while enumerating it. The ABI for the attribute remains
unchanged.

Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
---
v2: Add documentation

Documentation/ABI/testing/sysfs-bus-usb | 11 ------
.../ABI/testing/sysfs-devices-removable | 17 +++++++++
drivers/base/core.c | 28 +++++++++++++++
drivers/usb/core/hub.c | 8 ++---
drivers/usb/core/sysfs.c | 24 -------------
drivers/usb/core/usb.c | 1 +
include/linux/device.h | 36 +++++++++++++++++++
include/linux/usb.h | 7 ----
8 files changed, 86 insertions(+), 46 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-devices-removable

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index bf2c1968525f..73eb23bc1f34 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -154,17 +154,6 @@ Description:
files hold a string value (enable or disable) indicating whether
or not USB3 hardware LPM U1 or U2 is enabled for the device.

-What: /sys/bus/usb/devices/.../removable
-Date: February 2012
-Contact: Matthew Garrett <mjg@xxxxxxxxxx>
-Description:
- Some information about whether a given USB device is
- physically fixed to the platform can be inferred from a
- combination of hub descriptor bits and platform-specific data
- such as ACPI. This file will read either "removable" or
- "fixed" if the information is available, and "unknown"
- otherwise.
-
What: /sys/bus/usb/devices/.../ltm_capable
Date: July 2012
Contact: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
diff --git a/Documentation/ABI/testing/sysfs-devices-removable b/Documentation/ABI/testing/sysfs-devices-removable
new file mode 100644
index 000000000000..e13dddd547b5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-removable
@@ -0,0 +1,17 @@
+What: /sys/devices/.../removable
+Date: Apr 2021
+Contact: Matthew Garrett <mjg@xxxxxxxxxx>,
+ Rajat Jain <rajatja@xxxxxxxxxx>
+Description:
+ Information about whether a given device is physically fixed to
+ the platform. This is determined by the device's subsystem in a
+ bus / platform specific way. This attribute is only present for
+ buses that can support determining such information:
+
+ "removable": The device is external / removable from the system.
+ "fixed": The device is internal / fixed to the system.
+ "unknown": The information is unavailable.
+
+ Currently this is only supported by USB (which infers the
+ information from a combination of hub descriptor bits and
+ platform-specific data such as ACPI).
diff --git a/drivers/base/core.c b/drivers/base/core.c
index f29839382f81..b8ae4cc52805 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2327,6 +2327,25 @@ 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 *state;
+
+ switch (dev->removable) {
+ case DEVICE_REMOVABLE:
+ state = "removable";
+ break;
+ case DEVICE_FIXED:
+ state = "fixed";
+ break;
+ default:
+ state = "unknown";
+ }
+ return sprintf(buf, "%s\n", state);
+}
+static DEVICE_ATTR_RO(removable);
+
int device_add_groups(struct device *dev, const struct attribute_group **groups)
{
return sysfs_create_groups(&dev->kobj, groups);
@@ -2504,8 +2523,16 @@ static int device_add_attrs(struct device *dev)
goto err_remove_dev_online;
}

+ if (type && type->supports_removable) {
+ 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:
@@ -2525,6 +2552,7 @@ 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);
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 7f71218cc1e5..500e5648de04 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2442,11 +2442,11 @@ static void set_usb_port_removable(struct usb_device *udev)
*/
switch (hub->ports[udev->portnum - 1]->connect_type) {
case USB_PORT_CONNECT_TYPE_HOT_PLUG:
- udev->removable = USB_DEVICE_REMOVABLE;
+ dev_set_removable(&udev->dev, DEVICE_REMOVABLE);
return;
case USB_PORT_CONNECT_TYPE_HARD_WIRED:
case USB_PORT_NOT_USED:
- udev->removable = USB_DEVICE_FIXED;
+ dev_set_removable(&udev->dev, DEVICE_FIXED);
return;
default:
break;
@@ -2471,9 +2471,9 @@ static void set_usb_port_removable(struct usb_device *udev)
}

if (removable)
- udev->removable = USB_DEVICE_REMOVABLE;
+ dev_set_removable(&udev->dev, DEVICE_REMOVABLE);
else
- udev->removable = USB_DEVICE_FIXED;
+ dev_set_removable(&udev->dev, DEVICE_FIXED);

}

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index d85699bee671..e8ff3afdf7af 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -298,29 +298,6 @@ static ssize_t urbnum_show(struct device *dev, struct device_attribute *attr,
}
static DEVICE_ATTR_RO(urbnum);

-static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
- char *buf)
-{
- struct usb_device *udev;
- char *state;
-
- udev = to_usb_device(dev);
-
- switch (udev->removable) {
- case USB_DEVICE_REMOVABLE:
- state = "removable";
- break;
- case USB_DEVICE_FIXED:
- state = "fixed";
- break;
- default:
- state = "unknown";
- }
-
- return sprintf(buf, "%s\n", state);
-}
-static DEVICE_ATTR_RO(removable);
-
static ssize_t ltm_capable_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -825,7 +802,6 @@ static struct attribute *dev_attrs[] = {
&dev_attr_avoid_reset_quirk.attr,
&dev_attr_authorized.attr,
&dev_attr_remove.attr,
- &dev_attr_removable.attr,
&dev_attr_ltm_capable.attr,
#ifdef CONFIG_OF
&dev_attr_devspec.attr,
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index a566bb494e24..5a0f73a28196 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -523,6 +523,7 @@ struct device_type usb_device_type = {
#ifdef CONFIG_PM
.pm = &usb_device_pm_ops,
#endif
+ .supports_removable = true,
};

diff --git a/include/linux/device.h b/include/linux/device.h
index ba660731bd25..d6442b811607 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -93,6 +93,12 @@ struct device_type {
void (*release)(struct device *dev);

const struct dev_pm_ops *pm;
+
+ /*
+ * Determines whether the subsystem supports classifying the devices of
+ * this type into removable vs fixed.
+ */
+ bool supports_removable;
};

/* interface for exporting device attributes */
@@ -350,6 +356,19 @@ enum dl_dev_state {
DL_DEV_UNBINDING,
};

+/**
+ * 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_UNKNOWN: Device location is Unknown (default).
+ * @DEVICE_REMOVABLE: Device is removable by the user.
+ * @DEVICE_FIXED: Device is not removable by the user.
+ */
+enum device_removable {
+ DEVICE_REMOVABLE_UNKNOWN = 0,
+ DEVICE_REMOVABLE,
+ DEVICE_FIXED,
+};
+
/**
* struct dev_links_info - Device data related to device links.
* @suppliers: List of links to supplier devices.
@@ -431,6 +450,9 @@ 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().
@@ -541,6 +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;
@@ -778,6 +802,18 @@ 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 && dev->type && dev->type->supports_removable
+ && dev->removable == DEVICE_REMOVABLE;
+}
+
/*
* High level routines for use by the bus drivers
*/
diff --git a/include/linux/usb.h b/include/linux/usb.h
index d6a41841b93e..0bbb9e8b18c7 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -473,12 +473,6 @@ struct usb_dev_state;

struct usb_tt;

-enum usb_device_removable {
- USB_DEVICE_REMOVABLE_UNKNOWN = 0,
- USB_DEVICE_REMOVABLE,
- USB_DEVICE_FIXED,
-};
-
enum usb_port_connect_type {
USB_PORT_CONNECT_TYPE_UNKNOWN = 0,
USB_PORT_CONNECT_TYPE_HOT_PLUG,
@@ -701,7 +695,6 @@ struct usb_device {
#endif
struct wusb_dev *wusb_dev;
int slot_id;
- enum usb_device_removable removable;
struct usb2_lpm_parameters l1_params;
struct usb3_lpm_parameters u1_params;
struct usb3_lpm_parameters u2_params;
--
2.31.1.498.g6c1eba8ee3d-goog

Next message: Rajat Jain: "[PATCH v2 2/2] pci: Support "removable" attribute for PCI devices"
Previous message: Aline Santana Cordeiro: "Re: [Outreachy kernel] [PATCH v3] staging: media: atomisp: pci: Change line break to avoid an open parenthesis at the end of the line"
Next in thread: Rajat Jain: "[PATCH v2 2/2] pci: Support "removable" attribute for PCI devices"
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