[PATCH 3/4] virtio-iommu: Fix contradictory and unnecessary statements

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

In the device-normative statement for the ATTACH request, we say:

  If another endpoint is already attached to the domain identified by
  \field{domain}, then the device MAY attach the endpoint identified by
  \field{endpoint} to the domain.

and later:

  If properties of the endpoint (obtained with a PROBE request) are
  compatible with properties of other endpoints already attached to the
  requested domain, then the device SHOULD attach the endpoint.

These statements contradict each others. Attaching multiple endpoints to
one domain is a convenience that allows using fewer page table
resources. The device is always allowed to reject a second attach
request, in which case the driver simply creates a separate domain for
the second endpoint. Remove the "SHOULD" statement and keep the "MAY"
one.

Also remove the following statement which doesn't add anything useful.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 device-types/iommu/description.tex | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/device-types/iommu/description.tex b/device-types/iommu/description.tex
index c9b43db..fb1b840 100644
--- a/device-types/iommu/description.tex
+++ b/device-types/iommu/description.tex
@@ -383,12 +383,9 @@ \subsubsection{ATTACH request}\label{sec:Device Types / IOMMU Device / Device op
 VIRTIO_IOMMU_S_UNSUPP.
 
 If properties of the endpoint (obtained with a PROBE request) are
-compatible with properties of other endpoints already attached to the
-requested domain, then the device SHOULD attach the endpoint. Otherwise
-the device SHOULD reject the request and set \field{status} to
-VIRTIO_IOMMU_S_UNSUPP.
-
-A device that does not reject the request MUST attach the endpoint.
+not compatible with properties of other endpoints already
+attached to the domain, the device SHOULD reject the request and
+set \field{status} to VIRTIO_IOMMU_S_UNSUPP.
 
 \subsubsection{DETACH request}
 
-- 
2.41.0