linux-kernel - RE: [PATCH 2/4] fpga: dfl: Move DFH header register macros to linux/dfl.h

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Date:   Thu, 24 Jun 2021 04:45:43 +0000
From:   "Wu, Hao" <hao.wu@...el.com>
To:     "Xu, Yilun" <yilun.xu@...el.com>,
        Martin Hundebøll <mhu@...icom.dk>
CC:     Tom Rix <trix@...hat.com>, Moritz Fischer <mdf@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Martin Hundebøll <mhu@...nix.com>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        Debarati Biswas <debaratix.biswas@...el.com>,
        "Weight, Russell H" <russell.h.weight@...el.com>
Subject: RE: [PATCH 2/4] fpga: dfl: Move DFH header register macros to
  linux/dfl.h

> On Wed, Jun 23, 2021 at 01:56:59PM +0200, Martin Hundebøll wrote:
> >
> >
> > On 22/06/2021 09.39, Wu, Hao wrote:
> > > > On Mon, Jun 21, 2021 at 06:19:15PM +0800, Wu, Hao wrote:
> > > > > > Subject: [PATCH 2/4] fpga: dfl: Move DFH header register macros to
> > > > linux/dfl.h
> > > > > >
> > > > > > From: Debarati Biswas <debaratix.biswas@...el.com>
> > > > > >
> > > > > > Device Feature List (DFL) drivers may be defined in subdirectories other
> > > > > > than drivers/fpga, and each DFL driver should have access to the Device
> > > > > > Feature Header (DFH) register, which contains revision and type
> > > > > > information. This change moves the macros specific to the DFH register
> > > > > > from drivers/fpga/dfl.h to include/linux/dfl.h.
> > > > >
> > > > > Looks like it requires to access the revision info in the next patch,
> because
> > > > > current dfl_device doesn't expose related information.
> > > > >
> > > > > @Yilun, do you have any concern to expose those info via dfl_device?
> > > >
> > > > Exposing these header register definitions are good to me. These registers
> > > > are in DFL device's MMIO region, so it is good to share these info with
> > > > all DFL drivers.
> > >
> > > I mean expose revision via dfl_device, as dfl core already reads the DFL
> > > header, it sounds duplicate read in each dfl device driver. And if we
> > > consider this as a common need from dfl device driver, then the code
> > > can be moved to a common place as well.
> > >
> > > I hope from dfl device driver side, it doesn't need to know details of
> > > how DFH register is defined, only simple way from dfl device data
> > > structure or some simple helper function, then dfl device driver could
> > > know all common information from DFH.
> > >
> > > How do you think?
> 
> It's good idea.
> 
> >
> > struct dfl_device {} already has "u16 type" and "u16 feature_id", so it would
> make sense to add "u8 feature_rev" as well?
> 
> I think we may name it "u8 revision".

Sounds good.

Then we don't have to expose detailed registers information to such header file.
dfl_device data structure + helper function should be enough. : )

Thanks
Hao

> 
> Thanks,
> Yilun
> 
> >
> > // Martin