linux-kernel - Re: [PATCH v7 2/2] fpga: dfl: fme: add performance reporting support

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Message-ID: <20200212132045.GC1789899@kroah.com>
Date:   Wed, 12 Feb 2020 05:20:45 -0800
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Wu Hao <hao.wu@...el.com>
Cc:     Will Deacon <will@...nel.org>, mdf@...nel.org,
        mark.rutland@....com, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        atull@...nel.org, yilun.xu@...el.com,
        Luwei Kang <luwei.kang@...el.com>
Subject: Re: [PATCH v7 2/2] fpga: dfl: fme: add performance reporting support

On Wed, Feb 12, 2020 at 06:02:11PM +0800, Wu Hao wrote:
> On Tue, Feb 11, 2020 at 09:30:35PM -0800, Greg KH wrote:
> > On Wed, Feb 12, 2020 at 11:19:29AM +0800, Wu Hao wrote:
> > > On Mon, Feb 10, 2020 at 04:34:01PM +0000, Will Deacon wrote:
> > > > Hi,
> > > > 
> > > > On Mon, Feb 10, 2020 at 11:47:49AM +0800, Wu Hao wrote:
> > > > > This patch adds support for performance reporting private feature
> > > > > for FPGA Management Engine (FME). Now it supports several different
> > > > > performance counters, including 'basic', 'cache', 'fabric', 'vtd'
> > > > > and 'vtd_sip'. It allows user to use standard linux tools to access
> > > > > these performance counters.
> > > > 
> > > > I had a quick look at this, and it mostly looks alright to me. Just a few
> > > > high-level comments/questions:
> > > 
> > > Hi Will
> > > 
> > > Thanks a lot for the review! :)
> > > 
> > > > 
> > > >   - I would still prefer for the PMU drivers to live under drivers/perf/
> > > 
> > > Hm.. one possible way is to create a platform device, and introduce a new
> > > platform device driver under drivers/perf/.
> > 
> > No, do not abuse platform drivers, you have a real device, use it.
> 
> Sure, thanks for the comments. Then I don't have any other idea to move code to
> drivers/perf/ directory, so probably only can live with current code.

The location of the file in the kernel tree has no bearing on if you use
a platform device, a USB device, or a PCI device.  It is just a location
of a file.

You are interacting with the perf api as the driver's primary userspace
api, so put the driver into the drivers/perf/ directory.  That's all
that Will is asking you to do here.

greg k-h