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Diffstat (limited to 'Documentation/admin-guide/thunderbolt.rst')
| -rw-r--r-- | Documentation/admin-guide/thunderbolt.rst | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst index 898ad78f3cc7..10c4f0ce2ad0 100644 --- a/Documentation/admin-guide/thunderbolt.rst +++ b/Documentation/admin-guide/thunderbolt.rst @@ -1,6 +1,28 @@ -============= - Thunderbolt -============= +.. SPDX-License-Identifier: GPL-2.0 + +====================== + USB4 and Thunderbolt +====================== +USB4 is the public specification based on Thunderbolt 3 protocol with +some differences at the register level among other things. Connection +manager is an entity running on the host router (host controller) +responsible for enumerating routers and establishing tunnels. A +connection manager can be implemented either in firmware or software. +Typically PCs come with a firmware connection manager for Thunderbolt 3 +and early USB4 capable systems. Apple systems on the other hand use +software connection manager and the later USB4 compliant devices follow +the suit. + +The Linux Thunderbolt driver supports both and can detect at runtime which +connection manager implementation is to be used. To be on the safe side the +software connection manager in Linux also advertises security level +``user`` which means PCIe tunneling is disabled by default. The +documentation below applies to both implementations with the exception that +the software connection manager only supports ``user`` security level and +is expected to be accompanied with an IOMMU based DMA protection. + +Security levels and how to use them +----------------------------------- The interface presented here is not meant for end users. Instead there should be a userspace tool that handles all the low-level details, keeps a database of the authorized devices and prompts users for new connections. @@ -18,8 +40,6 @@ This will authorize all devices automatically when they appear. However, keep in mind that this bypasses the security levels and makes the system vulnerable to DMA attacks. -Security levels and how to use them ------------------------------------ Starting with Intel Falcon Ridge Thunderbolt controller there are 4 security levels available. Intel Titan Ridge added one more security level (usbonly). The reason for these is the fact that the connected devices can |