RE: [PATCH v3 1/2] Documentation: fpga: dfl: add PCI Identification documentation

[matthew . gerlach]

On Mon, 18 Jul 2022, Wu, Hao wrote:

> > -----Original Message-----
> > From: matthew.gerlach@xxxxxxxxxxxxxxx <matthew.gerlach@xxxxxxxxxxxxxxx>
> > Sent: Thursday, July 7, 2022 11:06 PM
> > To: Wu, Hao <hao.wu@xxxxxxxxx>; Xu, Yilun <yilun.xu@xxxxxxxxx>; Weight,
> > Russell H <russell.h.weight@xxxxxxxxx>; Muddebihal, Basheer Ahmed
> > <basheer.ahmed.muddebihal@xxxxxxxxx>; trix@xxxxxxxxxx;
> > mdf@xxxxxxxxxx; corbet@xxxxxxx; linux-fpga@xxxxxxxxxxxxxxx; linux-
> > doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Zhang, Tianfei
> > <tianfei.zhang@xxxxxxxxx>
> > Cc: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > Subject: [PATCH v3 1/2] Documentation: fpga: dfl: add PCI Identification
> > documentation
> >
> > From: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> >
> > Add documentation on identifying FPGA based PCI cards prompted
> > by discussion on the linux-fpga@xxxxxxxxxxxxxxx mailing list.
> >
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
> > ---
> > v3: Add url to page tracking PCI ID information for DFL based cards.
> >
> > v2: Introduced in v2.
> > ---
> >  Documentation/fpga/dfl.rst | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> >
> > diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> > index 15b670926084..5144775b860a 100644
> > --- a/Documentation/fpga/dfl.rst
> > +++ b/Documentation/fpga/dfl.rst
> > @@ -507,6 +507,27 @@ ids application.
> >  https://github.com/OPAE/dfl-feature-id
> >
> >
> > +PCI Device Identification
> > +================================
> > +Since FPGA based PCI cards can be reconfigured to a perform a completely
> > +new function at runtime, properly identifying such cards and binding the
> > +correct driver can be challenging. In many use cases, deployed FPGA based
> > +PCI cards are essentially static and the PCI Product ID and Vendor ID pair
> > +is sufficient to identify the card.  The DFL framework helps with the
> > +dynamic case of deployed FPGA cards changing at run time by providing
> > +more detailed information about card discoverable at runtime.
> > +
> > +At one level, the DFL on a PCI card describes the function of the card.
> > +However, the same DFL could be instantiated on different physical cards.
> > +Conversely, different DFLs could be instantiated on the same physical card.
> > +Practical management of a cloud containing a heterogeneous set of such
> > cards
> > +requires a PCI level of card identification. While the PCI Product ID and
> > +Vendor ID may be sufficient to bind the dfl-pci driver, it is expected
> > +that FPGA PCI cards would advertise suitable Subsystem ID and Subsystem
> > +Vendor ID values. Further PCI Product, Vendor, and Subsystem id tracking
> > +can be found at https://github.com/OPAE/dfl-feature-id/blob/main/dfl-pci-
> > ids.rst.
>
> I feel that we may not really need this in fpga-dfl doc, as this is not describing
> any new method provided by DFL, but just something from PCI standard, right?

I think you are correct that this documentation change is not necessary. 
It was useful as a mechanism for discussion, but it is really just 
something from the PCI standard.

I will not include it in the v4 patch set.

> Thanks
> Hao