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

From: Tom Rix
Date: Wed Jul 13 2022 - 18:07:23 EST

On 7/7/22 8:05 AM, matthew.gerlach@xxxxxxxxxxxxxxx wrote:
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.
+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

This link looks good.

It may be good to be explicit and say which device(s) needs to be specified by the quadruple.

Reviewed-by: Tom Rix <trix@xxxxxxxxxx>

Location of DFLs on a PCI Device
The original method for finding a DFL on a PCI device assumed the start of the