From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-804-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: From: "Dr. David Alan Gilbert (git)" Date: Fri, 12 Jul 2019 13:19:59 +0100 Message-Id: <20190712122002.10793-3-dgilbert@redhat.com> In-Reply-To: <20190712122002.10793-1-dgilbert@redhat.com> References: <20190712122002.10793-1-dgilbert@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [virtio-comment] [PATCH v7 2/5] pci: Define id field To: virtio-dev@lists.oasis-open.org, virtio-comment@lists.oasis-open.org, stefanha@redhat.com, cohuck@redhat.com Cc: vgoyal@redhat.com List-ID: From: "Dr. David Alan Gilbert" For the virtio-fs device we require multiple large shared memory regions. Differentiate these by an 'id' field in the base capability. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Cornelia Huck --- content.tex | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/content.tex b/content.tex index 6433226..fafa532 100644 --- a/content.tex +++ b/content.tex @@ -651,7 +651,8 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option u8 cap_len; /* Generic PCI field: capability length */ u8 cfg_type; /* Identifies the structure. */ u8 bar; /* Where to find it. */ - u8 padding[3]; /* Pad to full dword. */ + u8 id; /* Multiple capabilities of the same type */ + u8 padding[2]; /* Pad to full dword. */ le32 offset; /* Offset within bar. */ le32 length; /* Length of the structure, in bytes. */ }; @@ -697,7 +698,8 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option The device MAY offer more than one structure of any type - this makes it possible for the device to expose multiple interfaces to drivers. The order of the capabilities in the capability list specifies the order of preference - suggested by the device. + suggested by the device. A device may specify that this ordering mechanism be + overridden by the use of the \field{id} field. \begin{note} For example, on some hypervisors, notifications using IO accesses are faster than memory accesses. In this case, the device would expose two @@ -716,6 +718,12 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option Any other value is reserved for future use. +\item[\field{id}] + Used by some device types to uniquely identify multiple capabilities + of a certain type. If the device type does not specify the meaning of + this field, its contents are undefined. + + \item[\field{offset}] indicates where the structure begins relative to the base address associated with the BAR. The alignment requirements of \field{offset} are indicated -- 2.21.0 This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/