[PATCH v4 1/2] virtio-net: Describe dev cfg fields read only

[Parav Pandit <parav@nvidia.com>]

Device configuration fields are read only. Avoid duplicating this
description for multiple fields.

Instead describe it one time and do it in the driver requirements
section.

Fixes: https://github.com/oasis-tcs/virtio-spec/issues/161
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Signed-off-by: Parav Pandit <parav@nvidia.com>
---
changelog:
v3->v4:
- write driver requirement as normative statement
- add back read only wording in the description
v2->v3:
- split as new patch
---
 device-types/net/description.tex | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/device-types/net/description.tex b/device-types/net/description.tex
index 73501b6..821f7b0 100644
--- a/device-types/net/description.tex
+++ b/device-types/net/description.tex
@@ -156,25 +156,28 @@ \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network
 \subsection{Device configuration layout}\label{sec:Device Types / Network Device / Device configuration layout}
 \label{sec:Device Types / Block Device / Feature bits / Device configuration layout}
 
-Device configuration fields are listed below, they are read-only for a driver. The \field{mac} address field
-always exists (though is only valid if VIRTIO_NET_F_MAC is set), and
-\field{status} only exists if VIRTIO_NET_F_STATUS is set. Two
-read-only bits (for the driver) are currently defined for the status field:
-VIRTIO_NET_S_LINK_UP and VIRTIO_NET_S_ANNOUNCE.
+Device configuration fields are listed below. All the device
+configuration fields are read-only for the driver.
+
+The \field{mac} address field always exists (though is only
+valid if VIRTIO_NET_F_MAC is set), and \field{status} only
+exists if VIRTIO_NET_F_STATUS is set. Two bits are currently
+defined for the status field: VIRTIO_NET_S_LINK_UP and
+VIRTIO_NET_S_ANNOUNCE.
 
 \begin{lstlisting}
 #define VIRTIO_NET_S_LINK_UP     1
 #define VIRTIO_NET_S_ANNOUNCE    2
 \end{lstlisting}
 
-The following driver-read-only field, \field{max_virtqueue_pairs} only exists if
+The following field, \field{max_virtqueue_pairs} only exists if
 VIRTIO_NET_F_MQ or VIRTIO_NET_F_RSS is set. This field specifies the maximum number
 of each of transmit and receive virtqueues (receiveq1\ldots receiveqN
 and transmitq1\ldots transmitqN respectively) that can be configured once at least one of these features
 is negotiated.
 
-The following driver-read-only field, \field{mtu} only exists if
-VIRTIO_NET_F_MTU is set. This field specifies the maximum MTU for the driver to
+The following field, \field{mtu} only exists if VIRTIO_NET_F_MTU
+is set. This field specifies the maximum MTU for the driver to
 use.
 
 The following two fields, \field{speed} and \field{duplex}, only
@@ -264,6 +267,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
 
 \drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
 
+The driver MUST NOT write to any of the device configuration fields.
+
 A driver SHOULD negotiate VIRTIO_NET_F_MAC if the device offers it.
 If the driver negotiates the VIRTIO_NET_F_MAC feature, the driver MUST set
 the physical address of the NIC to \field{mac}.  Otherwise, it SHOULD
-- 
2.26.2