Re: [PATCH v4 1/2] driver core: Move the "removable" attribute from USB to core

From: Bjorn Helgaas
Date: Fri May 21 2021 - 16:54:11 EST

Next message: Stephen Boyd: "Re: [PATCH v4 1/2] drm/msm/dp: handle irq_hpd with sink_count = 0 correctly"
Previous message: Stephen Boyd: "Re: [PATCH v17 1/4] dt-bindings: msm: disp: add yaml schemas for DPU bindings"
In reply to: Greg Kroah-Hartman: "Re: [PATCH v4 1/2] driver core: Move the "removable" attribute from USB to core"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Thu, May 13, 2021 at 04:27:00PM -0700, Rajat Jain wrote:
> 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.

Looks nice!

Maybe the mini usage guide here could be a little more explicit, e.g.,

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.

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

Reviewed-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

Minor comment below, reviewed-by applies whether or not you do
anything.

> ---
> v4: - instead of devicce_type->supports_removable, add 1 more value in
> device_removable_enum
> - documentation update.
> - Remove "Acked-by" and "Reviewed-by" tags from previous versions.
> v3: - Minor commit log / comments updated.
> - use sysfs_emit()
> - Rename local variable name (state -> loc)
> - change supports_removable flag from bool to bitfield.
> 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 | 13 ++++---
> drivers/usb/core/sysfs.c | 24 ------------
> include/linux/device.h | 37 +++++++++++++++++++
> include/linux/usb.h | 7 ----
> 7 files changed, 89 insertions(+), 48 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..acf7766e800b
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-devices-removable
> @@ -0,0 +1,17 @@
> +What: /sys/devices/.../removable
> +Date: May 2021
> +Contact: Rajat Jain <rajatxjain@xxxxxxxxx>
> +Description:
> + Information about whether a given device can be removed from the
> + platform by the user. This is determined by its subsystem in a
> + bus / platform-specific way. This attribute is only present for
> + devices that can support determining such information:
> +
> + "removable": device can be removed from the platform by the user
> + "fixed": device is fixed to the platform / cannot be removed
> + by the user.
> + "unknown": The information is unavailable / cannot be deduced.
> +
> + 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 4a8bf8cda52b..ae3d6a4a79fb 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2404,6 +2404,25 @@ 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);
> @@ -2581,8 +2600,16 @@ 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:
> @@ -2602,6 +2629,7 @@ 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 b2bc4b7c4289..366cb7ef3b72 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2432,6 +2432,8 @@ static void set_usb_port_removable(struct usb_device *udev)
> u16 wHubCharacteristics;
> bool removable = true;
>
> + dev_set_removable(&udev->dev, DEVICE_REMOVABLE_UNKNOWN);
> +
> if (!hdev)
> return;
>
> @@ -2443,11 +2445,11 @@ 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;
> @@ -2472,9 +2474,9 @@ 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);
>
> }
>
> @@ -2546,8 +2548,7 @@ int usb_new_device(struct usb_device *udev)
> device_enable_async_suspend(&udev->dev);
>
> /* check whether the hub or firmware marks this port as non-removable */
> - if (udev->parent)
> - set_usb_port_removable(udev);
> + set_usb_port_removable(udev);
>
> /* Register the device. The device driver is responsible
> * for configuring the device and invoking the add-device
> diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
> index 5a168ba9fc51..fa2e49d432ff 100644
> --- a/drivers/usb/core/sysfs.c
> +++ b/drivers/usb/core/sysfs.c
> @@ -301,29 +301,6 @@ 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)
> {
> @@ -828,7 +805,6 @@ 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/include/linux/device.h b/include/linux/device.h
> index 38a2071cf776..e3a4749694b7 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -350,6 +350,22 @@ 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_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.
> @@ -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 && dev->removable == DEVICE_REMOVABLE;
> +}
> +
> +static inline bool dev_removable_is_valid(struct device *dev)
> +{
> + return dev && dev->removable != DEVICE_REMOVABLE_NOT_SUPPORTED;

I probably wouldn't check for "dev" being non-NULL in these two
functions unless you have a use case that requires it.

> +}
> +
> /*
> * High level routines for use by the bus drivers
> */
> diff --git a/include/linux/usb.h b/include/linux/usb.h
> index eaae24217e8a..b9bd664f44a1 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,
> @@ -703,7 +697,6 @@ 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;
> --
> 2.31.1.751.gd2f1c929bd-goog
>

Next message: Stephen Boyd: "Re: [PATCH v4 1/2] drm/msm/dp: handle irq_hpd with sink_count = 0 correctly"
Previous message: Stephen Boyd: "Re: [PATCH v17 1/4] dt-bindings: msm: disp: add yaml schemas for DPU bindings"
In reply to: Greg Kroah-Hartman: "Re: [PATCH v4 1/2] driver core: Move the "removable" attribute from USB to core"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]