[PATCH v1] virtio-can: define out of rage can-id and sdu

[PATCH v1] virtio-can: define out of rage can-id and sdu

[Matias Ezequiel Vara Larsen]

Explain when a message is out of range.

Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
---
v0 -> v1
    * Use length of the field wording to indicate out of range
    * Add when sdu length is out of range
---
 device-types/can/description.tex | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/device-types/can/description.tex b/device-types/can/description.tex
index 2511d9c..fa56abd 100644
--- a/device-types/can/description.tex
+++ b/device-types/can/description.tex
@@ -191,6 +191,14 @@ \subsubsection{Controller Mode}\label{sec:Device Types / CAN Device / Device Ope
 invalid state with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST
 NOT schedule the message for transmission.
 
+Note that the \field{can_id} field of a CAN frame is out of range when its
+length is more than 11 bits for standard frames or more than 29 bits for
+extended frames. The length of the \field{sdu} field is out of range when it
+uses more than 8 bytes for standard frames. If the VIRTIO_CAN_F_CAN_FD feature
+has been negotiated, the lenght of the \field{sdu} field is out of range when
+it uses more than 8 bytes and is not in the set [ 12, 16, 20, 24, 32, 48, 64 ]
+bytes.
+
 If the parameters are valid the message is scheduled for transmission.
 
 If feature VIRTIO_CAN_F_CAN_LATE_TX_ACK has been negotiated the

base-commit: 37c6a406678a5ee891fdf5671298cb4fcfa517f2
-- 
2.42.0

Re: [PATCH v1] virtio-can: define out of rage can-id and sdu

[Harald Mommer]

On 27.06.24 13:08, Matias Ezequiel Vara Larsen wrote:
> Explain when a message is out of range.
>
> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
> ---
> v0 -> v1
>      * Use length of the field wording to indicate out of range
>      * Add when sdu length is out of range
> ---
>   device-types/can/description.tex | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/device-types/can/description.tex b/device-types/can/description.tex
> index 2511d9c..fa56abd 100644
> --- a/device-types/can/description.tex
> +++ b/device-types/can/description.tex
> @@ -191,6 +191,14 @@ \subsubsection{Controller Mode}\label{sec:Device Types / CAN Device / Device Ope
>   invalid state with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST
>   NOT schedule the message for transmission.
>   
> +Note that the \field{can_id} field of a CAN frame is out of range when its
> +length is more than 11 bits for standard frames or more than 29 bits for
> +extended frames. The length of the \field{sdu} field is out of range when it
> +uses more than 8 bytes for standard frames. If the VIRTIO_CAN_F_CAN_FD feature
> +has been negotiated, the lenght of the \field{sdu} field is out of range when
> +it uses more than 8 bytes and is not in the set [ 12, 16, 20, 24, 32, 48, 64 ]
> +bytes.
> +
>   If the parameters are valid the message is scheduled for transmission.
>   
>   If feature VIRTIO_CAN_F_CAN_LATE_TX_ACK has been negotiated the
>
> base-commit: 37c6a406678a5ee891fdf5671298cb4fcfa517f2

"If the VIRTIO_CAN_F_CAN_FD feature has been negotiated, ..."

Would mean that sending a CAN classic frame having an sdu length > 8 
over a virtio CAN device capable to send also CAN FD frames would be 
allowed. This is not the case. The condition is the type of the actual 
CAN frame to be sent.

Decisive for CAN classic / CAN FD is the presence or absence of 
VIRTIO_CAN_FLAGS_FD in the flags.

Having an automatism to change a CAN classic frame to a CAN FD frame or 
the other way around under some conditions is not in the spec.

For example: "If the VIRTIO_CAN_FLAGS_FD bit is set in the 
\field{flags}, ..."

Or "If the frame is a CAN FD frame, ..."

Re: [PATCH v1] virtio-can: define out of rage can-id and sdu

[Matias Ezequiel Vara Larsen]

On Thu, Jun 27, 2024 at 03:16:35PM +0200, Harald Mommer wrote:
> 
> On 27.06.24 13:08, Matias Ezequiel Vara Larsen wrote:
> > Explain when a message is out of range.
> > 
> > Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
> > ---
> > v0 -> v1
> >      * Use length of the field wording to indicate out of range
> >      * Add when sdu length is out of range
> > ---
> >   device-types/can/description.tex | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> > 
> > diff --git a/device-types/can/description.tex b/device-types/can/description.tex
> > index 2511d9c..fa56abd 100644
> > --- a/device-types/can/description.tex
> > +++ b/device-types/can/description.tex
> > @@ -191,6 +191,14 @@ \subsubsection{Controller Mode}\label{sec:Device Types / CAN Device / Device Ope
> >   invalid state with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST
> >   NOT schedule the message for transmission.
> > +Note that the \field{can_id} field of a CAN frame is out of range when its
> > +length is more than 11 bits for standard frames or more than 29 bits for
> > +extended frames. The length of the \field{sdu} field is out of range when it
> > +uses more than 8 bytes for standard frames. If the VIRTIO_CAN_F_CAN_FD feature
> > +has been negotiated, the lenght of the \field{sdu} field is out of range when
> > +it uses more than 8 bytes and is not in the set [ 12, 16, 20, 24, 32, 48, 64 ]
> > +bytes.
> > +
> >   If the parameters are valid the message is scheduled for transmission.
> >   If feature VIRTIO_CAN_F_CAN_LATE_TX_ACK has been negotiated the
> > 
> > base-commit: 37c6a406678a5ee891fdf5671298cb4fcfa517f2
> 
> "If the VIRTIO_CAN_F_CAN_FD feature has been negotiated, ..."
> 
> Would mean that sending a CAN classic frame having an sdu length > 8 over a
> virtio CAN device capable to send also CAN FD frames would be allowed. This
> is not the case. The condition is the type of the actual CAN frame to be
> sent.
> 
> Decisive for CAN classic / CAN FD is the presence or absence of
> VIRTIO_CAN_FLAGS_FD in the flags.
> 
> Having an automatism to change a CAN classic frame to a CAN FD frame or the
> other way around under some conditions is not in the spec.
> 
> For example: "If the VIRTIO_CAN_FLAGS_FD bit is set in the \field{flags},
> ..."
> 
> Or "If the frame is a CAN FD frame, ..."
> 
> 

Thanks Harald, I will add it to v2.

Matias