From c037b6c818c30b6afa11dc70018fc4a075f26028 Mon Sep 17 00:00:00 2001 From: Rajat Jain Date: Mon, 24 May 2021 10:18:12 -0700 Subject: 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 Signed-off-by: Rajat Jain Link: https://lore.kernel.org/r/20210524171812.18095-2-rajatja@google.com Signed-off-by: Greg Kroah-Hartman --- Documentation/ABI/testing/sysfs-devices-removable | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'Documentation/ABI/testing/sysfs-devices-removable') diff --git a/Documentation/ABI/testing/sysfs-devices-removable b/Documentation/ABI/testing/sysfs-devices-removable index acf7766e800b..bda6c320c8d3 100644 --- a/Documentation/ABI/testing/sysfs-devices-removable +++ b/Documentation/ABI/testing/sysfs-devices-removable @@ -14,4 +14,5 @@ Description: 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). + platform-specific data such as ACPI) and PCI (which gets this + from ACPI / device tree). -- cgit v1.2.3