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

[Matias Ezequiel Vara Larsen <mvaralar@redhat.com>]

On Wed, Jun 26, 2024 at 01:07:17PM +0200, Harald Mommer wrote:
> 
> On 21.06.24 16:27, Matias Ezequiel Vara Larsen wrote:
> > On Wed, Jun 05, 2024 at 10:42:19AM +0200, Stefano Garzarella wrote:
> > > On Tue, May 21, 2024 at 04:11:42PM GMT, Matias Ezequiel Vara Larsen wrote:
> > > > Explain when a message is out of range.
> > > > 
> > > > Signed-off-by: Matias Ezequiel Vara Larsen<mvaralar@redhat.com>
> > > > ---
> > > > * This patch applies on top of virtio-1.4, which has not been released
> > > >   yet.
> > > > ---
> > > > device-types/can/description.tex | 3 +++
> > > > 1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/device-types/can/description.tex b/device-types/can/description.tex
> > > > index 2511d9c..98b163b 100644
> > > > --- a/device-types/can/description.tex
> > > > +++ b/device-types/can/description.tex
> > > > @@ -191,6 +191,9 @@ \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 a message is out of range when a standard frame uses more than 11
> > > > +bits of \field{can_id} or when an extended frame uses more than 29 bits.
> > > > +
> > > 
> Non-extended CAN frame and can_id contains more than 11 bits (not in range
> 0..7FFH) => broken.
> 
> Extended CAN frame and can_id contains more than 29 bits (not in range
> 0..1FFFFFFFH) => broken.
> 
> See also 5.20.3 "Feature bits", there it's mentioned but not this
> prominently.
> 
> Classic CAN frame and sdu length > 8 bytes => broken.
> 
> Comes from ISO 11898-1:2015, should have been mentioned more clearly here as
> it was done in 5.20.3. There is not stated that the allowed value range is
> 0..8. Obvious for CAN people, not obvious for anybody else.
> 
> CAN FD frame and sdu length > 8 bytes and not in the set { 12, 16, 20, 24,
> 32, 48, 64 } bytes => broken.
> 
> Comes from ISO 11898-1:2015, is not obvious for people not too familiar with
> CAN FD and is missing in the virtio CAN specification.
> 
> This is what was meant. Now some good wording is needed.
> 
> 
Thanks Harald! I'll add it in v1.

Matias