Re: [PATCH v3 1/4] Documentation: fpga: dfl: Add documentation for DFHv1

[matthew . gerlach]

On Wed, 5 Oct 2022, Ilpo Järvinen wrote:

> On Tue, 4 Oct 2022, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
>
> > From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> >
> > Add documentation describing the extensions provided by Version
> > 1 of the Device Feature Header (DFHv1).
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > ---
> > v3: no change
> >
> > v2: s/GUILD/GUID/
> >     add picture
> > ---
> >  Documentation/fpga/dfl.rst | 49 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >
> > diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> > index 15b670926084..7c786b75b498 100644
> > --- a/Documentation/fpga/dfl.rst
> > +++ b/Documentation/fpga/dfl.rst
> > @@ -561,6 +561,55 @@ new DFL feature via UIO direct access, its feature id should be added to the
> >  driver's id_table.
> >
> >
> > +Extending the Device Feature Header - DFHv1
> > +===========================================
> > +The current 8 bytes of the Device Feature Header, hereafter referred to as
> > +to DFHv0, provide very little opportunity for the hardware to describe itself
> > +to software. Version 1 of the Device Feature Header (DFHv1) is being introduced
> > +to provide increased flexibility and extensibility to hardware designs using
> > +Device Feature Lists.  The list below describes some of the goals behind the
> > +changes in DFHv1:
> > +
> > +* Provide a standardized mechanism for features to describe
> > +  parameters/capabilities to software.
> > +* Standardize the use of a GUID for all DFHv1 types.
> > +* Decouple the location of the DFH from the register space of the feature itself.
> > +
> > +Modeled after PCI Capabilities, DFHv1 Parameters provide a mechanism to associate
> > +a list of parameter values to a particular feature.
> > +
> > +With DFHv0, not all features types contained a GUID.  DFHv1 makes the GUID standard
> > +across all types.
> > +
> > +With DFHv0, the register map of a given feature is located immediately following
> > +the DFHv0 in the memory space.  With DFHv1, the location of the feature register
> > +map can be specified as an offset to the DFHv1 or as an absolute address.  The DFHv1
> > +structure is shown below:
>
> I think this is not a good place for be some kind of v1 marketing speak
> (that said, I think it's fine to include those goals you have there).

I understand the need to avoid marketing speak here.  I will update to 
just state the facts.

> I'd restructure this so that this section only talks about DFHv1 w/o
> any comparing how v1 is better than v0. Don't base the description on
> how things changed from v0 but just describe v1, that is, like v1 is
> already there, not only being introduced to supercede/extend v0.
>
> And then create v0 section after this section which focuses solely on v0.

I agree that separate sections simply describing v0 and v1 would be 
better.  I may describe v0 first since it shares some fields with v1.

> --
> i.
>
> > +    +-----------------------------------------------------------------------+
> > +    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 VER 12|11 ID 0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_L                             0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_H                             0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Address/Offset                            1|  Rel  0|
> > +    +-----------------------------------------------------------------------+
> > +    |63 Size of register set  32|Params 31|30 Group    16|15 Instance      0|
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0|
> > +    +-----------------------------------------------------------------------+
> > +
> > +                                  ...
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0|
> > +    +-----------------------------------------------------------------------+
> > +
> >  Open discussion
> >  ===============
> >  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration