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| -rw-r--r-- | virtio-v1.0-wd01-part1-specification.txt | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt index 2d7a0fe..cfbb60f 100644 --- a/virtio-v1.0-wd01-part1-specification.txt +++ b/virtio-v1.0-wd01-part1-specification.txt @@ -232,6 +232,21 @@ Thus drivers should read configuration space fields like so: Note that configuration space generally uses the little-endian format for multi-byte fields. +Note that future versions of this specification will likely +extend the configuration space for devices by adding extra fields +at the tail end of some structures in configuration space. + +To allow forward compatibility with such extensions, drivers must +not limit structure size and configuration space size. Instead, +drivers should only check that configuration space is *large enough* to +contain the fields required for device operation. + +For example, if the specification states that configuration +space 'includes a single 8-bit field' drivers should understand this to mean that +the configuration space can also include an arbitrary amount of +tail padding, and accept any configuration space size equal to or +greater than the specified 8-bit size. + 100.100.4.1. Legacy Interface: A Note on Configuration Space endian-ness -------------------------------------- @@ -1071,6 +1086,20 @@ struct virtio_pci_cap { This structure can optionally followed by extra data, depending on other fields, as documented below. +Note that future versions of this specification will likely +extend devices by adding extra fields at the tail end of some structures. + +To allow forward compatibility with such extensions, drivers must +not limit structure size. Instead, drivers should only +check that structures are *large enough* to contain the fields +required for device operation. + +For example, if the specification states 'structure includes a +single 8-bit field' drivers should understand this to mean that +the structure can also include an arbitrary amount of tail padding, +and accept any structure size equal to or greater than the +specified 8-bit size. + The fields are interpreted as follows: cap_vndr |