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linux/Documentation/ABI/testing/sysfs-devices-removable

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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>
2021-05-25 01:18:11 +08:00
What: /sys/devices/.../removable
Date: May 2021
Contact: Rajat Jain <rajatxjain@gmail.com>
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:
ABI: sysfs-devices-removable: make a table valid as ReST markup Changeset 70f400d4d957 ("driver core: Move the "removable" attribute from USB to core") added a table to the file, but not using a valid ReST format. Change it to avoid build issues when producing documentation with "make htmldocs". Fixes: 70f400d4d957 ("driver core: Move the "removable" attribute from USB to core") Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/bf83354747b8abaa486fe03af4be2826363469cb.1632740376.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-09-27 19:10:55 +08:00
=========== ===================================================
"removable" device can be removed from the platform by the user
"fixed" device is fixed to the platform / cannot be removed
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>
2021-05-25 01:18:11 +08:00
by the user.
ABI: sysfs-devices-removable: make a table valid as ReST markup Changeset 70f400d4d957 ("driver core: Move the "removable" attribute from USB to core") added a table to the file, but not using a valid ReST format. Change it to avoid build issues when producing documentation with "make htmldocs". Fixes: 70f400d4d957 ("driver core: Move the "removable" attribute from USB to core") Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/bf83354747b8abaa486fe03af4be2826363469cb.1632740376.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-09-27 19:10:55 +08:00
"unknown" The information is unavailable / cannot be deduced.
=========== ===================================================
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>
2021-05-25 01:18:11 +08:00
Currently this is only supported by USB (which infers the
information from a combination of hub descriptor bits and
PCI: Add sysfs "removable" attribute A PCI device is "external_facing" if it's a Root Port with the ACPI "ExternalFacingPort" property or if it has the DT "external-facing" property. We consider everything downstream from such a device to be removable by user. We're mainly concerned with consumer platforms with user accessible Thunderbolt ports that are vulnerable to DMA attacks, and we expect those ports to be identified by firmware as "ExternalFacingPort". Devices in traditional hotplug slots can technically be removed, but the expectation is that unless the port is marked with "ExternalFacingPort", such devices are less accessible to user / may not be removed by end user, and thus not exposed as "removable" to userspace. This can be used to implement userspace policies tailored for user removable devices. Eg usage: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2591812 https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2795038 (code uses such an attribute to remove external PCI devices or disable features on them as needed by the policy desired) Acked-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Rajat Jain <rajatja@google.com> Link: https://lore.kernel.org/r/20210524171812.18095-2-rajatja@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-25 01:18:12 +08:00
platform-specific data such as ACPI) and PCI (which gets this
from ACPI / device tree).
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