[virtio-dev] Re: [PATCH 02/11] transport-pci: Move transitional device id to legacy section

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Mar 31, 2023 at 01:58:25AM +0300, Parav Pandit wrote:
> Currently PCI device discovery details for the transitional device
> are documented in two different sections.
> 
> For example, PCI device and vendor ID registers are documented in
> 'Device Requirements: PCI Device Discovery' section, while PCI
> revision id is documented in 'Legacy Interfaces: A Note on PCI
> Device Discovery' section.
> 
> Transitional devices requirements should be documented in "legacy
> interfaces" section as clearly mentioned in
> 'Legacy Interface: A Note on Feature Bits'.

I already commented on this, I disagree.
Modern drivers must be able
to completely ignore legacy interface sections, but they
do bind to transitional device IDs.
This change breaks this assumption.


> Hence,
> 1. Move transitional device requirements to its designated Legacy
>    interface section
> 2. Describe regular device requirements without quoting it as "non
>    transitional device"
> 
> While at it, write the description using a singular object definition.
> 
> Reviewed-by: Satananda Burla <sburla@marvell.com>
> Signed-off-by: Parav Pandit <parav@nvidia.com>
> ---
>  transport-pci.tex | 70 ++++++++++++++++++++++++-----------------------
>  1 file changed, 36 insertions(+), 34 deletions(-)
> 
> diff --git a/transport-pci.tex b/transport-pci.tex
> index 7f27107..1f74c6f 100644
> --- a/transport-pci.tex
> +++ b/transport-pci.tex
> @@ -28,46 +28,24 @@ \subsection{PCI Device Discovery}\label{sec:Virtio Transport Options / Virtio Ov
>  
>  \devicenormative{\subsubsection}{PCI Device Discovery}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}
>  
> -Devices MUST have the PCI Vendor ID 0x1af4.
> -Devices MUST either have the PCI Device ID calculated by adding 0x1040
> +The device MUST have the PCI Vendor ID 0x1af4.
> +The device MUST calculate PCI Device ID by adding 0x1040
>  to the Virtio Device ID, as indicated in section \ref{sec:Device
> -Types} or have the Transitional PCI Device ID depending on the device type,
> -as follows:
> -
> -\begin{tabular}{|l|c|}
> -\hline
> -Transitional PCI Device ID  &  Virtio Device    \\
> -\hline \hline
> -0x1000      &   network device     \\
> -\hline
> -0x1001     &   block device     \\
> -\hline
> -0x1002     & memory ballooning (traditional)  \\
> -\hline
> -0x1003     &      console       \\
> -\hline
> -0x1004     &     SCSI host      \\
> -\hline
> -0x1005     &  entropy source    \\
> -\hline
> -0x1009     &   9P transport     \\
> -\hline
> -\end{tabular}
> +Types}.
>  
>  For example, the network device with the Virtio Device ID 1
> -has the PCI Device ID 0x1041 or the Transitional PCI Device ID 0x1000.
> -
> -The PCI Subsystem Vendor ID and the PCI Subsystem Device ID MAY reflect
> -the PCI Vendor and Device ID of the environment (for informational purposes by the driver).
> +has the PCI Device ID 0x1041.
>  
> -Non-transitional devices SHOULD have a PCI Device ID in the range
> -0x1040 to 0x107f.
> -Non-transitional devices SHOULD have a PCI Revision ID of 1 or higher.
> -Non-transitional devices SHOULD have a PCI Subsystem Device ID of 0x40 or higher.
> +The device SHOULD have a PCI Device ID in the range 0x1040 to 0x107f.
> +The device SHOULD have a PCI Revision ID of 1 or higher.
> +The device SHOULD have a PCI Subsystem Device ID of 0x40 or higher.
>  
>  This is to reduce the chance of a legacy driver attempting
>  to drive the device.
>  
> +The PCI Subsystem Vendor ID and the PCI Subsystem Device ID MAY reflect
> +the PCI Vendor and Device ID of the environment (for informational purposes by the driver).
> +
>  \drivernormative{\subsubsection}{PCI Device Discovery}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}
>  Drivers MUST match devices with the PCI Vendor ID 0x1af4 and
>  the PCI Device ID in the range 0x1040 to 0x107f,
> @@ -85,8 +63,32 @@ \subsection{PCI Device Discovery}\label{sec:Virtio Transport Options / Virtio Ov
>  PCI Subsystem Device ID value.
>  
>  \subsubsection{Legacy Interfaces: A Note on PCI Device Discovery}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery / Legacy Interfaces: A Note on PCI Device Discovery}
> -Transitional devices MUST have a PCI Revision ID of 0.
> -Transitional devices MUST have the PCI Subsystem Device ID
> +
> +The transitional device has one of the following PCI Device ID
> +depending on the device type:
> +
> +\begin{tabular}{|l|c|}
> +\hline
> +Transitional PCI Device ID  &  Virtio Device    \\
> +\hline \hline
> +0x1000      &   network device     \\
> +\hline
> +0x1001     &   block device     \\
> +\hline
> +0x1002     & memory ballooning (traditional)  \\
> +\hline
> +0x1003     &      console       \\
> +\hline
> +0x1004     &     SCSI host      \\
> +\hline
> +0x1005     &  entropy source    \\
> +\hline
> +0x1009     &   9P transport     \\
> +\hline
> +\end{tabular}
> +
> +The transitional device MUST have a PCI Revision ID of 0.
> +The transitional device MUST have the PCI Subsystem Device ID
>  matching the Virtio Device ID, as indicated in section \ref{sec:Device Types}.
>  Transitional devices MUST have the Transitional PCI Device ID in
>  the range 0x1000 to 0x103f.
> -- 
> 2.26.2


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