[Qemu-devel] [PATCH v2 virtio 1/1] Add "Group Identifier" to virtio PCI capabilities.

[Venu Busireddy]

Add VIRTIO_PCI_CAP_GROUP_ID_CFG (Group Identifier) capability to the
virtio PCI capabilities to allow for the grouping of devices.

Signed-off-by: Venu Busireddy <address@hidden>
---
 content.tex | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/content.tex b/content.tex
index be18234..27581c1 100644
--- a/content.tex
+++ b/content.tex
@@ -599,6 +599,8 @@ The fields are interpreted as follows:
 #define VIRTIO_PCI_CAP_DEVICE_CFG        4
 /* PCI configuration access */
 #define VIRTIO_PCI_CAP_PCI_CFG           5
+/* Group Identifier */
+#define VIRTIO_PCI_CAP_GROUP_ID_CFG      6
 \end{lstlisting}
 
         Any other value is reserved for future use.
@@ -997,6 +999,40 @@ address \field{cap.length} bytes within a BAR range
 specified by some other Virtio Structure PCI Capability
 of type other than \field{VIRTIO_PCI_CAP_PCI_CFG}.
 
+\subsubsection{Group Identifier capability}\label{sec:Virtio Transport Options 
/ Virtio Over PCI Bus / PCI Device Layout / Group Identifier capability}
+
+The VIRTIO_PCI_CAP_GROUP_ID_CFG capability provides means for grouping devices 
together.
+
+The capability is immediately followed by an identifier of arbitrary size as 
below:
+
+\begin{lstlisting}
+struct virtio_pci_group_id_cap {
+        struct virtio_pci_cap cap;
+        u8 group_id[]; /* Group Identifier */
+};
+\end{lstlisting}
+
+The fields \field{cap.bar}, \field{cap.length}, \field{cap.offset}
+and \field{group_id} are read-only for the driver.
+
+The specification does not impose any restrictions on the structure
+or size of group_id[], except that the size must be a multiple of 4.
+Devices are free to declare this array as large as needed, as long as
+the combined size of all capabilities can be accommodated within the
+PCI configuration space.
+
+The field \field{cap.cap_len} indicates the length of the group identifier
+\field{group_id}. The fields \field{cap.bar}, \field{cap.offset} and
+\field{cap.length} should be set to 0.
+
+\devicenormative{\paragraph}{Group Identifier capability}{Virtio Transport 
Options / Virtio Over PCI Bus / PCI Device Layout / Group Identifier capability}
+
+The device MAY present the VIRTIO_PCI_CAP_GROUP_ID_CFG capability.
+
+\drivernormative{\paragraph}{Group Identifier capability}{Virtio Transport 
Options / Virtio Over PCI Bus / PCI Device Layout / Group Identifier capability}
+
+The driver MUST NOT write to group_id[] area.
+
 \subsubsection{Legacy Interfaces: A Note on PCI Device 
Layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device 
Layout / Legacy Interfaces: A Note on PCI Device Layout}
 
 Transitional devices MUST present part of configuration