[RFC PATCH 2/4] fpga: Add new properties to support user-key encrypted bitstream loading

[Nava kishore Manne]

Hi Rob,

	Please find my response inline.

> -----Original Message-----
> From: Rob Herring <robh at kernel.org>
> Sent: Thursday, May 13, 2021 8:05 PM
> To: Nava kishore Manne <navam at xilinx.com>
> Cc: mdf at kernel.org; trix at redhat.com; Michal Simek <michals at xilinx.com>;
> arnd at arndb.de; Rajan Vaja <RAJANV at xilinx.com>;
> gregkh at linuxfoundation.org; linus.walleij at linaro.org; Amit Sunil Dhamne
> <amitsuni at xlnx.xilinx.com>; Tejas Patel <tejasp at xlnx.xilinx.com>;
> zou_wei at huawei.com; Manish Narani <MNARANI at xilinx.com>; Sai Krishna
> Potthuri <lakshmis at xilinx.com>; Jiaying Liang <jliang at xilinx.com>; linux-
> fpga at vger.kernel.org; devicetree at vger.kernel.org; linux-
> kernel at vger.kernel.org; linux-arm-kernel at lists.infradead.org; git
> <git at xilinx.com>; chinnikishore369 at gmail.com
> Subject: Re: [RFC PATCH 2/4] fpga: Add new properties to support user-key
> encrypted bitstream loading
> 
> On Thu, May 13, 2021 at 5:55 AM Nava kishore Manne <navam at xilinx.com>
> wrote:
> >
> > Hi Rob,
> >
> >         Please find my response inline.
> >
> > > -----Original Message-----
> > > From: Rob Herring <robh at kernel.org>
> > > Sent: Thursday, May 13, 2021 8:01 AM
> > > To: Nava kishore Manne <navam at xilinx.com>
> > > Cc: mdf at kernel.org; trix at redhat.com; Michal Simek
> > > <michals at xilinx.com>; arnd at arndb.de; Rajan Vaja
> <RAJANV at xilinx.com>;
> > > gregkh at linuxfoundation.org; linus.walleij at linaro.org; Amit Sunil
> > > Dhamne <amitsuni at xlnx.xilinx.com>; Tejas Patel
> > > <tejasp at xlnx.xilinx.com>; zou_wei at huawei.com; Manish Narani
> > > <MNARANI at xilinx.com>; Sai Krishna Potthuri <lakshmis at xilinx.com>;
> > > Jiaying Liang <jliang at xilinx.com>; linux- fpga at vger.kernel.org;
> > > devicetree at vger.kernel.org; linux- kernel at vger.kernel.org;
> > > linux-arm-kernel at lists.infradead.org; git <git at xilinx.com>;
> > > chinnikishore369 at gmail.com
> > > Subject: Re: [RFC PATCH 2/4] fpga: Add new properties to support
> > > user-key encrypted bitstream loading
> > >
> > > On Tue, May 04, 2021 at 03:52:25PM +0530, Nava kishore Manne wrote:
> > > > This patch Adds ‘encrypted-key-name’ and
> > > > ‘encrypted-user-key-fpga-config’ properties to support user-key
> > > > encrypted bitstream loading use case.
> > > >
> > > > Signed-off-by: Nava kishore Manne <nava.manne at xilinx.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/fpga/fpga-region.txt | 5 +++++
> > > >  1 file changed, 5 insertions(+)
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/fpga/fpga-region.txt
> > > > b/Documentation/devicetree/bindings/fpga/fpga-region.txt
> > > > index d787d57491a1..957dc6cbcd9e 100644
> > > > --- a/Documentation/devicetree/bindings/fpga/fpga-region.txt
> > > > +++ b/Documentation/devicetree/bindings/fpga/fpga-region.txt
> > > > @@ -177,6 +177,9 @@ Optional properties:
> > > >     it indicates that the FPGA has already been programmed with
> > > > this
> > > image.
> > > >     If this property is in an overlay targeting a FPGA region, it is a
> > > >     request to program the FPGA with that image.
> > > > +- encrypted-key-name : should contain the name of an encrypted
> > > > +key file
> > > located
> > > > +   on the firmware search path. It will be used to decrypt the
> > > > + FPGA
> > > image
> > > > +   file.
> > > >  - fpga-bridges : should contain a list of phandles to FPGA
> > > > Bridges that must
> > > be
> > > >     controlled during FPGA programming along with the parent FPGA
> > > bridge.
> > > >     This property is optional if the FPGA Manager handles the bridges.
> > > > @@ -187,6 +190,8 @@ Optional properties:
> > > >  - external-fpga-config : boolean, set if the FPGA has already
> > > > been
> > > configured
> > > >     prior to OS boot up.
> > > >  - encrypted-fpga-config : boolean, set if the bitstream is
> > > > encrypted
> > > > +- encrypted-user-key-fpga-config : boolean, set if the bitstream
> > > > +is
> > > encrypted
> > > > +   with user key.
> > >
> > > What's the relationship with encrypted-fpga-config? Both present or
> > > mutually exclusive? Couldn't this be implied by encrypted-key-name
> > > being present?
> > >
> >
> > In Encryption we have two kinds of use case one is Encrypted Bitstream
> > loading with Device-key and Other one is Encrypted Bitstream loading
> > with User-key. encrypted-fpga-config and
> > encrypted-user-key-fpga-config are mutually exclusive. To differentiate
> both the use cases I have added this new flag and Aes Key file(encrypted-key-
> name) is needed only for encrypted-user-key-fpga-config use cases.
> 
> If encrypted-key-name is required for a user key, then why do you need
> encrypted-user-key-fpga-config also?
> 
> IOW, why have 3 properties (that's 9 possible combinations) for 2 modes?
> 

Agree, we can use encrypted-key-name for user-key use cases instead of having both encrypted-key-name and encrypted-user-key-fpga-config flags.
Will fix this issue in v2.

Regards,
Navakishore.