diff options
| author | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-03-15 10:07:13 +0000 |
|---|---|---|
| committer | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-03-15 10:07:13 +0000 |
| commit | 4e0739635b32261aea9c05c17081a20be7c00cb6 (patch) | |
| tree | 850efbcb5c536c9bad35dc2fd24acdbced1f0f0e /content.tex | |
| parent | db517375409ca452cdb80f6b8f82b349424f36cd (diff) | |
ccw: allow WRITE_STATUS to fail
We want to be able to fail setting a status on the device (e.g.
FEATURES_OK if the device can't work with the features negotiated).
The easiest way to do that is to allow the device to fail the
WRITE_STATUS command by posting a command reject.
VIRTIO-116
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Approved unanimously:
https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=2762
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@479 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
Diffstat (limited to 'content.tex')
| -rw-r--r-- | content.tex | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/content.tex b/content.tex index 6a8638b..1efe93a 100644 --- a/content.tex +++ b/content.tex @@ -2595,6 +2595,23 @@ The driver changes the status of a device via the CCW_CMD_WRITE_STATUS command, which transmits an 8 bit status value. +As described in +\ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits}, +a device sometimes fails to set the \field{status} field: For example, it +might fail to accept the FEATURES_OK status bit during device initialization. + +\drivernormative{\paragraph}{Communicating Status Information}{Virtio Transport Options / Virtio over channel I/O / Device Initialization / Communicating Status Information} + +If the device posts a unit check with command reject in response to the +CCW_CMD_WRITE_STATUS command, the driver MUST assume that the device failed +to set the status and the \field{status} field retained its previous value. + +\devicenormative{\paragraph}{Communicating Status Information}{Virtio Transport Options / Virtio over channel I/O / Device Initialization / Communicating Status Information} + +If the device fails to set the \field{status} field to the value written by +the driver, the device MUST assure that the \field{status} field is left +unchanged and MUST post a unit check with command reject. + \subsubsection{Handling Device Features}\label{sec:Virtio Transport Options / Virtio over channel I/O / Device Initialization / Handling Device Features} Feature bits are arranged in an array of 32 bit values, making |